Planning and scheduling in the digital factory

Production planning and scheduling with the aid of software tools in today’s manufacturing industries have become a common practice which is indispensable for providing high level customer service, and at the same time to utilize the production resources, like workforce, machine tools, raw materials, energy, etc., efficiently. To meet the new requirements, problem modeling tools, optimization techniques, and visualization of data and results have become part of the software packages. In this chapter some recent developments in problem modeling and optimization techniques applied to important and challenging industrial planning and scheduling problems are presented. We will focus on new problem areas which are still at the edge of current theoretical research, but they are motivated by practical needs. On the one hand, we will discuss project based production planning, and on the other hand, we will tackle a resource leveling problems in a machine environment. We will present the problems, some modeling and solution approaches, and various extensions and applications

Inhomogeneities and caustics in the sedimentation of noninertial particles in incompressible flows

In an incompressible flow, fluid density remains invariant along fluid element trajectories. This implies that the spatial distribution of non-interacting noninertial particles in such flows cannot develop density inhomogeneities beyond those that are already introduced in the initial condition. However, in certain practical situations, density is measured or accumulated on (hyper-) surfaces of dimensionality lower than the full dimensionality of the flow in which the particles move. An example is the observation of particle distributions sedimented on the floor of the ocean. In such cases, even if the initial distribution of noninertial particles is uniform within a finite support in an incompressible flow, advection in the flow will give rise to inhomogeneities in the observed density. In this paper we analytically derive, in the framework of an initially homogeneous particle sheet sedimenting towards a bottom surface, the relationship between the geometry of the flow and the emerging distribution. From a physical point of view, we identify the two processes that generate inhomogeneities to be the stretching within the sheet, and the projection of the deformed sheet onto the target surface. We point out that an extreme form of inhomogeneity, caustics, can develop for sheets. We exemplify our geometrical results with simulations of particle advection in a simple kinematic flow, study the dependence on various parameters involved, and illustrate that the basic mechanisms work similarly if the initial (homogeneous) distribution occupies a more general region of finite extension rather than a sheet.Comment: 56 pages, 17 figure

A vállalati informatika szerepe a versenyképesség alakításában a pénzügyi és gazdasági válság időszakában (Corporate IT in shaping the competitiveness of the Hungarian enterprises in the financial and economic crisis)

A cikk az informatika és a versenyképesség kapcsolatát vizsgálja. A Budapesti Corvinus Egyetem Versenyképesség Kutatási Programjának korábbi felmérései óta számos új technológia bukkant fel, illetve hazánkat is elérte a világméretű pénzügyi és gazdasági válság hatása. E kihívások tükrében érdemesnek tűnt újra megvizsgálni az információtechnológia (IT) szerepét a versenyképesség alakításában. / === / In this paper the relationship between information technology (IT) and competitiveness is tackled. Since the authors’ previous surveys within their Competitiveness Research Program several new technologies have emerged, and the influence of the word wide financial and economic crisis has reached Hungary as well. In the face of these challenges it is worth reexamining the role of IT in shaping the competitive position of companies. The structure of the paper is as follows. A brief theoretical introduction is provided before their research questionsare presented. After that, the paper contains an analysis on selected fields of the corporate IT function, namely IT infrastructure, IT applications, IT management and IT strategy. Based on this, conclusions are made both at the end of the main parts, and in the final section of the paper. As far as the final conclusions are concerned, the majority of respondents do not regard IT today as a source of sustainable or contestable competitive advantage, though the dominant opinion underlines that IT is a strategic necessity. Besides this, their research results suggest a kind of association between corporate performance and the maturity level of the IT function. However, even the best performing companies are not prepared yet to effectively respond to their own prediction that forecasts the strengthening role of IT as a competitive factor

Car Sequencing with respect to Regular Expressions and Linear Bounds

In this paper we introduce a new model and a computational approach for sequencing assembly lines with two types of constraints: (i) patterns described by regular expressions and (ii) linear bounds on the number of certain products that may occur in pre-specified intervals. If we restrict the problem to the second type of constraints only we obtain a generalization of the familiar car sequencing problem, whereas constraints of type (i) may be useful to add extra structure. Constraints of both types may have priorities and can be violated, and a Pareto optimal solution is sought minimizing the violation of constraints in the given priority order. We describe a computational method based on mathematical programming and genetic algorithms for finding suboptimal solutions

Vállalati közösségi média – A személyközi hálózatok motorja

Napjainkban a szervezetek és személyek hálózatos összekapcsolódása a nemzetközi vezetéstudományi szakirodalom egyik legmeghatározóbb témája. A vállalati közösségi média – mint a hálózatosodást támogató technológia – meglehetősen gyorsan vált népszerűvé, noha pontos tartalma még formálódik, és szervezeti hatásairól is keveset tudunk. A szerzők ismertetik a vállalati közösségi média fontosabb meghatározásait, majd áttekintik az elmúlt évek témával foglalkozó nemzetközi szakirodalmát. Tanulmányukban a vállalati közösségi médiát a személyközi hálózatok motorjaként értelmezik, amelynek működését összevetik az offline tér hálózataival. A szerzők saját kvalitatív kutatásuk alapján ismertetik egy hazai tudásintenzív iparágban működő szervezet vállalati közösségimédia-használatának legfontosabb szervezeti funkcióit

Scheduling of inventory releasing jobs to minimize a regular objective function of delivery times

In this note we provide new complexity and algorithmic results for scheduling inventory releasing jobs, a new class of single machine scheduling problems proposed recently by Boysen et al. We focus on tardiness related criteria, while known results are concerned with inventory levels between fixed delivery points. Our interest is motivated by the fact that deciding whether a feasible schedule exists is NP-hard in the strong sense, provided that all delivery deadlines are fixed, and there are no restrictions on the amount of products released by the jobs, nor on the job processing times. We will establish NP-hardness results, or provide polynomial or pseudo-polynomial time algorithms for various special cases, and describe a fully polynomial approximation scheme for one of the variants with the maximum tardiness criterion. © 2012 Springer Science+Business Media New York