Formulations for a problem of petroleum transportation

Oil tankers play a fundamental role in every offshore petroleum supply chain and due to its high price, it is essential to optimize its use. Since this optimization requires handling detailed operational aspects, complete optimization models are typically intractable. Thus, a usual approach is to solve a tactical level model prior to optimize the operational details. In this case, it is desirable that tactical models are as precise as possible to avoid too severe adjustments in the next optimization level. In this paper, we study tactical models for a crude oil transportation problem by tankers. We did our work on the top of a previous paper found in the literature. The previous model considers inventory capacities and discrete lot sizes to be transported, aiming to meet given demands over a finite time horizon. We compare several formulations for this model using 50 instances from the literature and proposing 25 new harder ones. A column generation-based heuristic is also proposed to find good feasible solutions with less computational burden than the heuristics of the commercial solver used.     

The electric field in the conductive half space as a model in mining and petroleum prospecting

We present a formulation of Maxwell's equations in a conductive medium, in the time domain. In order to restrict the equations to the conductive half space, the solution in the air is represented by an integral boundary operator on the interface. The problem admits a variational formulation, allowing a finite element solution. A mathematical analysis is described for 2D and 3D models, and numerical results are presented.     

Models for operads

We study properties of differential graded (dg) operads modulo weak equivalences, that is, modulo the relation given by the existence of a chain of dg operad maps including a homology isomorphism. This approach, naturally arising in string theory, leads us to consider various versions of models. Some applications in topology (homotopy-everything spaces), algebra (cotangent cohomology) and mathematical physics (closed string-field theory) - are also given     

Models for products

This paper explores how models can support productive thinking. For us a model is a thing, a tool to help make sense of something. We restrict attention to specific models for whole-number multiplication, hence the wording of the title. They support evolving thinking in large measure through the ways their users redesign them. They assume new forms, come to be seen and understood in different ways. We show how work that learners do with models can help them to transform, not simply their understanding of key concepts, but also how they come to view themselves as thinkers and learners, as collaborators in a social process that their work and thinking help to constitute. We draw on recent research on core knowledge, especially by Carey, Spelke, and Tomasello, to clarify how models, as we view them here, can underpin specific actions that support emerging understanding.     

Models for purchase frequency

Purchase frequency modeling began with the pioneering work of Ehrenberg [Ehrenberg, A.S.C., 1959. The pattern of consumer purchases. Applied Statistics 8, 26–41]. This note provides an extension of this work. A collection of some seventeen flexible distributions is discussed for purchase frequency modeling. The corresponding estimation procedures are derived by the method of moments and the method of maximum likelihood. An application is illustrated to a consumer purchasing data used by Ehrenberg.     

Models for transporation networks

Various stochastic models are proposed for transportation networks, by increasing order of complexity. The mathematical tools rely on queueing theory and asymptotic analysis. These models are mainly applied to service vehicle systems, like PRAXITELE, but the methods used are more far-reaching. In particular, the asymptotic independence of nodes is proved in the thermodynamical limit, i.e., when the volume of the system increases. Proceedings of the XVII Seminar on Stability Problems for Stochastic Models, Kazan, Russian, 1995. Part III.     

Models for singularity categories

In this article we construct various models for singularity categories of modules over differential graded rings. The main technique is the connection between abelian model structures, cotorsion pairs and deconstructible classes, and our constructions are based on more general results about localization and transfer of abelian model structures. We indicate how recollements of triangulated categories can be obtained model categorically, discussing in detail Krause?s recollement _Kac(Inj(R))→K(Inj(R))→D(R)${\mathrm{K}}_{\mathrm{ac}}(\mathrm{Inj}(R))\to \mathrm{K}(\mathrm{Inj}(R))\to \mathrm{D}(R)$. In the special case of curved mixed Z$\mathbb{Z}$-graded complexes, we show that one of our singular models is Quillen equivalent to Positselski?s contraderived model for the homotopy category of matrix factorizations.     

群的一个Domain结构

群可以通过在其上赋予循环群拓扑构造群的Domain模型，从而实现群的可计算性。群上的循环群偏序集及其对偶都是连续的偏序集，这个连续偏序集是代数Domain的充分必要条件是群的单位元是代数元。如果在pseudo-有限的群G及其循环群偏序集的对偶￡^op[G]上分别赋予循环群拓扑和Scott拓扑，那么恒同函数是连续的。     

Models for network evolution

This paper describes mathematical models for network evolution when ties (edges) are directed and the node set is fixed. Each of these models implies a specific type of departure from the standard null binomial model. We provide statistical tests that, in keeping with these models, are sensitive to particular types of departures from the null. Each model (and associated test) discussed follows directly from one or more socio‐cognitive theories about how individuals alter the colleagues with whom they are likely to interact. The models include triad completion models, degree variance models, polarization and balkanization models, the Holland‐Leinhardt models, metric models, and the constructural model. We find that many of these models, in their basic form, tend asymptotically towards an equilibrium distribution centered at the completely connected network (i.e., all individuals are equally likely to interact with all other individuals); a fact that can inhibit the development of satisfactory tests.     

Optimal exploitation for hybrid systems of renewable resources under partial observation

This work focuses on optimal controls for hybrid systems of renewable resources in random environments. We propose a new formulation to treat the optimal exploitation with harvesting and renewing. The random environments are modeled by a Markov chain, which is hidden and can be observed only in a Gaussian white noise. We use the Wonham filter to estimate the state of the Markov chain from the observable process. Then we formulate a harvesting–renewing model under partial observation. The Markov chain approximation method is used to find a numerical approximation of the value function and optimal policies. Our work takes into account natural aspects of the resource exploitation in practice: interacting resources, switching environment, renewing and partial observation. Numerical examples are provided to demonstrate the results and explore new phenomena arising from new features in the proposed model.     

A simple linear model for the optimal exploitation of renewable resources

This paper describes a simple linearized model for the optimal control of a natural resource stock. Applications of the model to fisheries and forestry, as well as to mineral exploration and recovery, are discussed.Research supported partially by the National Research Council of Canada, Grant A-3990.     

Balancing exploration and exploitation with adaptive variation for evolutionary multi-objective optimization

Although recent studies have shown that evolutionary algorithms are effective tools for solving multi-objective optimization problems, their performances are often bottlenecked by the suitability of the evolutionary operators with respect to the optimization problem at hand and their corresponding parametric settings. To adapt the search dynamic of evolutionary operation in multi-objective optimization, this paper proposes an adaptive variation operator that exploits the chromosomal structure of binary representation and synergizes the function of crossover and mutation. The overall search ability is deterministically tuned online to maintain a balance between extensive exploration and local fine-tuning at different stages of the evolutionary search. Also, the coordination between the two variation operators is achieved by means of an adaptive control that ensures an efficient exchange of information between the different chromosomal sub-structures throughout the evolutionary search. Extensive comparative studies with several representative variation operators are performed on different benchmark problems and significant algorithmic performance improvements in terms of proximity, uniformity and diversity are obtained with the incorporation of the proposed adaptive variation operator into the evolutionary multi-objective optimization process.     

Approximate Deconvolution Models for Magnetohydrodynamics

We consider the family of approximate deconvolution models (ADM) for the simulation of the large eddies in turbulent viscous, incompressible, electrically conducting flows. We prove the existence and uniqueness of solutions to the ADM-MHD equations, their weak converge to the solution of the MHD equations as the averaging radii tend to zero, and derive a bound on the modeling error. We demonstrate that the energy and helicity of the models are conserved, and the models preserve the Alfvén waves. We provide the results of the computational tests, that verify the accuracy and physical fidelity of the models.