Analysis of performance of an iron-bath reactor using computational fluid dynamics

The performance of an iron-bath reactor has been studied using a comprehensive numerical model that combines a computational fluid dynamics approach for the gas phase and a heat and mass balance model for the bath. The model calculates:

• •coal, ore, flux and oxygen consumption;
• •post-combustion ratio (PCR);
• •heat-transfer efficiency (HTE);
• •off-gas temperature and composition;
• •heat transfer and chemical reactions between gas and iron and slag droplets; and
• •heat transfer between gas and bath, refractories and lance.

The model was validated with data reported by the Nippon Steel Corporation for a 100 t pilot plant, and the calculated and measured data are in good agreement. Modelling results showed that the dominant mechanisms of heat transfer from the gas to the bath are radiation to the slag surface and convection heat transfer to droplets.     

On degree sequences of undirected,directed, and bidirected graphs

Bidirected graphs generalize directed and undirected graphs in that edges are oriented locally at every node. The natural notion of the degree of a node that takes into account (local) orientations is that of net-degree. In this paper, we extend the following four topics from (un)directed graphs to bidirected graphs:

• –Erdős–Gallai-type results: characterization of net-degree sequences,
• –Havel–Hakimi-type results: complete sets of degree-preserving operations,
• –Extremal degree sequences: characterization of uniquely realizable sequences, and
• –Enumerative aspects: counting formulas for net-degree sequences.

To underline the similarities and differences to their (un)directed counterparts, we briefly survey the undirected setting and we give a thorough account for digraphs with an emphasis on the discrete geometry of degree sequences. In particular, we determine the tight and uniquely realizable degree sequences for directed graphs.     

Multiparametric demand transportation problem

In some applications a minimum cost transportation model arises where supplies are fixed while demands may simultaneously vary. In this paper we analyse the structure of such a model and propose several techniques to describe its behaviour. Our approach is founded on the concept of optimal region, i.e., the subset of demand vectors where a given basic tree is optimal. The proposed algorithm consists in different pivoting strategies designed to:

• 1.build up a minimal list of basic trees such that the associated optimal regions cover the set of feasible demand vectors;
• 2.analyse the effects of either opening a new supplier or closing an existing one;
• 3.suitably treat the dual degenerate case by building up a minimal representation of every maximal region where the optimal value is linear in the demand vector.

Computational complexity is discussed and numerical examples are given.     

Maximizing profit of a food retailing chain by targeting and promoting valuable customers using Loyalty Card and Scanner Data

In this paper, we set up a House of Profit Model, an approach of maximizing profit of a food retailing chain by targeting and promoting valuable customers. Our model combines

• •segmentation analysis of households using Loyalty Card and Scanner Data,
• •price and promotion elasticity analysis,
• •simulation of effects of pricing and promotion,
• •price and promotion optimization to maximize profit.

These components are well-known in the literature and each of them has received considerable independent study. However, in this study we combine each of these components into one consistent, application-orientated model. We then demonstrate using panel data that the combination has a synergic effect on the efficiency of estimation and the maximization of profit (e.g., price and promotion elasticity estimation is improved by conducting it within market segments rather than across an entire hetereogeneous population). These estimates are further improved by incorporating “pass through”—a functional relationship between a retailer’s unit prices and unit costs.     

An optimal time to sleep for an auto-sleep system considering multi-usage states

An auto-sleep system is defined by the following two properties:

• 1.(i) a call for the system occurs randomly and intermittently
• 2.(ii) the system automatically goes to sleep if there occurs no call during a prespecified time T.

It considers four states:

• 1.(a) sleep
• 2.(b) warm-up
• 3.(c) nonusage
• 4.(d) usage.

For such a system, the time to sleep has been discussed based on suitable criteria. This study extends the model for an auto-sleep system so that the model can deal with multi-usage states. With a view to determining an optimal time to sleep under the extended model, the expected energy consumed per unit time is formulated as a criterion to be minimized. The existence of an optimal time to sleep is examined under a general call distribution. Numerical examples are also provided for a Weibull as well as a log-normal call distribution.     

A Note on Old Babylonian Computational Techniques

Analysis of the errors in two Old Babylonian “algebraic” problems shows

• •that the computations were performed on a device where additive contributions were no longer identifiable once they had entered the computation;
• •that this device must have been some kind of counting board or abacus where numbers were represented as collections of calculi;
• •that units and tens were represented in distinct ways, perhaps by means of different calculi.

© 2002 Elsevier Science (USA).Eine Analyse der Rechenfehler in zwei altbabylonischen “algebraischen” Aufgaben läßt mehrere Rückschlüsse auf ein Hilfsmittel zu, das zur Durchführung von Rechnungen benutzt worden sein kann:

• •Additive Beiträge waren nach ihrer Eintragung in die Rechnung nicht länger identifizierbar.
• •Das Gerät war eine Art Rechenbrett, auf welchem Zahlen als Haufen von Rechensteinen erschienen.
• •Einer und Zehner wurden in verschiedener Weise, evtl. mittels verschiedener Rechensteine repräsentiert.

© 2002 Elsevier Science (USA).MSC subject classification: 01A17.     

Chirurgies d'indice un et isotopies de sphères dans les variétés de contact tendues

We prove the following theorems:

• 1)Any surgery of index one on u tight contact manifold (of dimension three) gives rise to a manifold which carries a natural tight contact structure.
• 2)In a tight contact manifold, any two isotopic spheres which carry the same characteristic foliation are isotopic through a contact isolopy.
• 3)In a tight contact manifold, any two isotopic spheres have isomorphic complements.

     

Free energy and solutions of the Vlasov-Poisson-Fokker-Planck system: external potential and confinement (Large time behavior and steady states)

This paper is devoted to the characterization of external electrostatic potentials for which the Vlasov-Poisson-Fokker-Planck system satisfies one of the following properties:

• (i) the system admits stationary solutions,
• (ii) any solution to the evolution problem converges to a stationary solution, or, equivalently, no mass vanishes for large times,
• (iii) the free energy is bounded from below, We give conditions under which these different notions of confinement are equivalent.

     

An historical reenactment of the battle of Gettysburg on Janus (Army)

Utilizing Janus (A), we analyzed the decision made by LTG Richard Ewell at Gettysburg, PA on the evening of 1 July, 1863. At this time, LTG Ewell decided not to attack Culp's Hill. Instead, he waited until the next morning to attack, to permit the mustering of both artillery support and his third division, under command of MG Johnson. Many historians contend that this was a poor tactical decision and was a direct cause of the confederate loss at Gettysburg and possibly the war. We have investigated this issue using a combat simulation model called Janus (Army).Prerequisite to the simulation, systems and weapons of the time had to be modeled in the Janus database. To keep this relatively manageable, we decided to model only the most significant system types on each side. These included the Confederate and Yankee soldier armed with a bayonet and a non-repeating rifle; the cannoneer and cannon (12 Ib ball and cannister-shot) on each side. In total, the simulation represented nearly 200,000 systems engaged at Gettysburg.Our study employed a two level, two factor experimental design. The two factors were the presence of the corp's artillery and Johnson's division. Both factors were relevant to the decision to delay the confederate attack. The levels corresponded with whether or not each factor was used in the simulation. In all, we conducted three replications of the following four design points (tactical alternatives) from which to base our conclusions:

• 1.Design Point 1 (B): Situation on 1 Jul 1863 (no change). Ewell's Corps attacks.
• 2.Design Point 2 (B+A): Corps Artillery supports the attack.
• 3.Design Point 3 (B+J): MG Johnson's Division participates in attack.
• 4.Design Point 4 (B+A+J): Corps Artillery supports and MG Johnson's Division participates in attack.We conclude that LTG Ewell made the correct tactical decision. Without either his corps artillery or Johnson's Division, the corps would have faced annihilation should he have attacked on 1 July. Had he had his corps artillery (6 guns), he probably should have pushed aggressively up the hill. If he had only Johnson's division, he probably could have taken the hill but could not have held it as a tenable position for very long.

     

Improved OR education through the use of spreadsheet models

The first and major part of this presentation shows how OR education may be improved through the use of spreadsheets, with several examples:

• •in decision theory, where the drawing capabilities of Excel are used to represent decision trees and where window switching and macros allow the educator to animate his presentation;
• •in linear programming, where the solver is used (remarks are made relating to the adequacy of the solver's solutions), and where the spreadsheet's graphing capabilities are used both to represent the feasible set and the objective function, and to interactively animate the objective function or constraint movements;
• •in dynamic programming, deterministic or stochastic, where it is shown that several standard spreadsheet functions facilitate the development of specialized models;
• •in simulation, where it will be seen how stochastic simulation may be facilitated through the use of an add-in, and how a decision support system may thus be built from scratch in less than 10 minutes.

A creative use of the spreadsheet in business OR models is presented in the second part of this presentation, with an example in process simulation: airport luggage traffic simulation. A short third part presents the possibilities offered by spreadsheet add-ins.     

The dynamic programming method in the generalized traveling salesman problem

A procedure of the dynamic programming (DP) for the discrete-continuous problem of a route optimization is considered. It is possible to consider this procedure as a dynamic method of optimization of the towns choice in the well-known traveling salesman problem. In the considered version of DP, elements of a dynamic optimization are used. Two variants of the function of the aggregations of losses are investigated:

• 1.(1) the additive functions;
• 2.(2) the function characterizing the aggregation of losses in the bottle-neck problem.

     

Modelling the motion of a three-link manipulator based on a plane with a time-dependent inclination

This work deals with the modelling of a three-link manipulator mounted on a plane with a time-dependent inclination. Two cases are considered.

• (i)The plane is part of a rigid body.
• (ii)The plane is in a moored ship.

     

Probabilistic inequalities and remarks

The authors use their recently proved integral inequality to obtain bounds for the covariance of two random variables

• 1.in a general setup and
• 2.for a class of special joint distributions.

The same inequality is also used to estimate the difference of the expectations of two random variables. Finally, the authors study the attainability of a related inequality.     

Common knowledge revisited

We consider the common-knowledge paradox raised by Halpern and Moses: common knowledge is necessary for agreement and coordination, but common knowledge is unattainable in the real world because of temporal imprecision. We discuss two solutions to this paradox:

• 1.(1) modeling the world with a coarser granularity, and
• 2.(2) relaxing the requirements for coordination.

     

Symplectic geometry,minors and graph Laplacians

In my talk, I will present some works done in the nineties on Laplacians on graphs: from eigenvalue problems to inverse problem for resistor networks. I will focus on the motivations and the main results as well as on the main ideas:

• •A differential topology point of view on the minor relation: a nice stratification associated to a finite graph Γ whose strata are associated to the minors of Γ
• •“Discrete” (graphs) versus “continuous” (Riemannian manifolds)
• •Stability of spectra with respect to singular limits: a finite dimensional theory of operators with domains (Von Neumann theory).

The link with topology will appear in some results about my graph parameter μ, in particular the planarity and the linkless embedding properties.     

System dynamics and feedback control problem formulations for real time dynamic traffic routing

This paper formulates the Dynamic Traffic Routing (DTR) problem as a real-time feedback control problem. Three different forms of the formulation are presented:

• 1.(1) distributed parameter system form derived from the conservation law;
• 2.(2) space discretized continuous lumped parameter form;
• 3.(3) space and time discretized lumped parameter form.

These formulations can be considered as the starting points for development of feedback control laws for the different control problems stated in this paper. This paper presents the feedback control problems, and does not discuss in detail the methodology of solution techniques which could be used to solve these problems. However, for the sake of completeness a brief treatment of the three forms are included in this paper to show possible ways to design the controllers.     

Formal aspects of egress complexity

Egress complexity is concerned with the summative uncertainty experienced by a naive occupant of a building when faced with a challenge to evacuate without the assistance of signage. This paper takes the present model of egress complexity and recasts its basic initiative in terms of elementary order theory. Arguments are presented to demonstrate

• •the existence of distinct maximum and minimum exit complexities for a given number of compartments,
• •the monotonic nature of complexity and
• •the relationship of a given floorplan complexity to the corresponding measures of its homomorphic images

The uniqueness of the theory on which the model is developed stems from a scenario-independent nonmetric approach to egress measurement.