On Wrinkling in Sandwich Panels with an Orthotropic Core

This paper deals with the local loss of stability (wrinkling) problem of a thin facing of a sandwich panel. Classical solutions to the problem of a facing instability resting on a homogeneous and isotropic substructure (a core) are compared. The relations between strain energy components associated with different forms of core deformations are discussed. Next, a new solution for the orthotropic core is presented in detail, which is consistent with the classic solution for the isotropic core. Selected numerical examples confirm the correctness of the analytical formulas. In the last part, parametric analyses are carried out to illustrate the sensitivity of wrinkling stress to a change in the material parameters of the core. These analyses illustrate the possibility of using the equations derived in the article for the variability of Poisson’s ratio from −1 to 1 and for material parameters strongly deviating from isotropy.

On the classic Solution of Fuzzy Linear Matrix Equations

Since most time-dependent models may be represented as linear or non-linear dynamical systems, fuzzy linear matrix equations are quite general in signal processing, control and system theory. A uniform method of finding the classic solution of fuzzy linear matrix equations is presented in this paper. Conditions of solution existence are also studied here. Under the framework, a numerical method to solve fuzzy generalized Lyapunov matrix equations is developed. In order to show the validation and efficiency, some selected examples and numerical tests are presented.

Thick-Wall Elastic Collapse for Casing Design

Summary Elastic collapse is an important piece of the tubular collapse formulation in API TR 5C3 (2008) and ISO/TR 10400 (2007). Elastic collapse is significant because it is independent of the strength of the tubing, for example, K-55 and Q-125 have the same resistance to elastic collapse. Advanced collapse models, such as Klever and Tamano (2006), require a thick-wall collapse result as part of their formulation. What would the effect of a thick wall have on elastic collapse? There really is no way to tell from the classic formulation. The primary issue is whether the elastic collapse formula overpredicts or underpredicts collapse pressure. The developers of the API collapse equation thought the thin-wall equation overpredicted collapse pressure and put in terms to reduce the predictions. Other studies suggested the opposite effect. What is needed is a formulation that is based on an elastic solution for a thick-wall cylinder, but that can derive the classic solution for a thin wall. The elastic equations for a thick-walled cylinder exist, known as the Kirsch equations (Kirsch 1898). A new set of physically reasonable boundary conditions are proposed for the Kirsch equation, which was then used to determine the collapse resistance for a thick-wall pipe. This result also yielded the classic result in the limit because t/D is small. The thick-wall elastic collapse formula is then applied to the standard API TR 5C3 (2008) collapse formulation and to the Klever-Tamano formulation (Klever and Tamano 2006).

ELECTROMOBILITY TOPICS ENTERING A NEW DECADE

During the last ten years the electric vehicles became more and more part of the daily mobility. Supported by different policies, but also by the technology advance, the electromobility is far to be an achieved topic and enters a new decade. The hybrid solutions continue to offer an alternative using the combustion engines. Latest researches and developments on fuel cells push to an alternative future, based on hydrogen. The electric batteries, as energy storage on vehicle, remain the most important way to conduct EV to the roads, with regular improvements. In fact, all these technologies are developing solutions to provide and control the energy for an electric motor. The classic solution using one engine and a kinematic chain to distribute the mechanical power to the wheels is completed by the possibility to integrate not only one, but more electric motors in the same vehicle.

Competitive Equilibrium with Indivisible Goods and Generic Budgets

Competitive equilibrium from equal incomes (CEEI) is a classic solution to the problem of fair and efficient allocation of goods (Foley 1967, Varian 1974). Every agent receives an equal budget of artificial currency with which to purchase goods, and prices match demand and supply. However, a CEEI is not guaranteed to exist when the goods are indivisible even in the simple two-agent, single-item market. Yet it is easy to see that, once the two budgets are slightly perturbed (made generic), a competitive equilibrium does exist. In this paper, we aim to extend this approach beyond the single-item case and study the existence of equilibria in markets with two agents and additive preferences over multiple items. We show that, for agents with equal budgets, making the budgets generic—by adding vanishingly small random perturbations—ensures the existence of equilibrium. We further consider agents with arbitrary nonequal budgets, representing nonequal entitlements for goods. We show that competitive equilibrium guarantees a new notion of fairness among nonequal agents and that it exists in cases of interest (such as when the agents have identical preferences) if budgets are perturbed. Our results open opportunities for future research on generic equilibrium existence and fair treatment of nonequals.

Determination of the efforts in two-way slabs of concrete through the finite difference method

From the implementation of analytical solutions for thin rectangular slabs using the Finite Difference Method, the present paper was developed with the purpose of comparing the determined efforts in a concrete plate with those that would be found using the tables originated from the plates theory of authors established in the literature. For this, the programming language Python was used, taking as a case study, a slab with dimensions of 5 meters long by 3 meters wide and thickness equal to 0.10 meters. In the analysis of the efforts, several support conditions were considered, in which the internal efforts and displacements obtained by the Finite Difference Method were compared with the results obtained through the tables proposed in literature. It was verified that the Finite Difference Method constitutes a good alternative for the resolution of thin solid plates, since the results were similar to the classic solution proposed in literature. The implemented program allows the visualization of the efforts through of spectrums of zone which facilitates the understanding of the distribution of the efforts along the slab, differing slightly from the uniform distribution adopted in the tables consulted.

COMPOSITE BINDERS FOR FINISHING COMPOSITIONS

Belgorod region is one of the leading regions in housing construction, especially private households. This is due to the high demand for finishing materials, in particular, dry plaster and putty mixtures, produced mainly on the basis of gypsum. However, local producers of such products can hardly compete with imported products due to lower prices. The reason for this is the absence in Belgorod Region, as in many other regions of Russia, of gypsum deposits and, as a result, its rather high cost exceeds that of Portland cement. Such a situation makes the actual development of cement-based finishing mixtures, corresponding to gypsum consumer qualities. The main problems of obtaining plaster compositions based on Portland cement is its excessive activity, low water-holding capacity and, as a result, poor workability and adhesion to the base. The classic solution to this problem is the introduction of a fine component (clay or lime) into such a solution, which makes the solution suitable for plastering, but does not allow Portland cement to realize its strength potential, therefore, does not ensure the effectiveness of its use. Giving the cement-sand mortar the desired properties due to polymer modifiers (structuring and thickening) is unjustified due to their high cost and high consumption. In this regard, at this stage of research, the task was to obtain a mineral system based on Portland cement with properties maximally adapted to obtain plaster mixtures, in order to further produce its modification with the above-mentioned additives at their minimum consumption. Composite binders consisting of a clinker part and a mineral additive were chosen as a tool for solving the problem posed. Due to the choice of the ratio of components, their type and dispersion, processing modes, it is possible to vary the properties of the products obtained within considerable limits.

Research and the Approval Process: The Organization of Persuasion

An informer sequentially collects and disseminates information through costly research to persuade an evaluator to approve an activity. Payoffs and control rights are split between informer and evaluator depending on the organizational rules governing the approval process. The welfare benchmark corresponds to Wald’s classic solution for a statistician with payoff equal to the sum of informer and evaluator. Organizations with different commitment power of informer and evaluator are compared from a positive and normative perspective. Granting authority to the informer is socially optimal when information acquisition is sufficiently costly. The analysis is applied to the regulatory process for drug approval. (JEL D82, D83, I18, L51, L65, O31)