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.     

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.     

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.     

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.     

单指标模型的统计推断

本文对单指标模型的统计推断方法进行了系统阐述,其中包括联系函数和指标系数的估计,经验似然,模型检验和变量选择等。本文的取材来自近二十年来的最新研究成果。     

Models for petroleum field exploitation

This paper presents some models for an early evaluation of a petroleum field. Based on crude assumptions about a reservoir, our models suggest decisions concerning platform capacity, drilling programme and production. We start out with a simple production planning model using linear programming. By mixed integer programming techniques the model is gradually extended. The most sophisticated version of the model can propose platform capacity, where and when wells should be drilled, and the production from the wells. The models are tested on numerical examples, and the results are discussed. From the experiments we conclude that the problems are very hard to solve, and that the size of problems that can be solved is limited by the computational burden. Finally we give some ideas for future work that may provide better solution methods.