Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

This paper describes an implementation of the Task Algebra, a formal model of hierarchical tasks and workflows, inthe Haskell programming language. Previously we presented the Task Algebra as a formal, unambiguous notationcapturing the kinds of activity and workflow typically seen in business analysis diagrams, similar to UML use case andactivity diagrams. Here, we show how the abstract syntax for the Task Algebra may be parsed and then semanticallyanalysed, by a suite of Haskell functions, to compute the execution traces of a system. The approach is illustratedwith a case study of a journal management system. The results show how it is possible to automate the semanticanalysis of requirements diagrams, as a precursor to developing a logical design.

Effective planning of a transportation network influences tactical and operational activities and has a great impact onbusiness. Planning typically considers multiple aspects such as variable transportation costs, various levels ofcustomer service offered, security of goods, and traveling time. These aspects often vary with time. Although theminimum cost flow problem is a widely seen approach to configure a transportation network, there is no much workconsidering variations on arcs; even more, the problem with varying nodes has hardly been addressed. In this work isdeveloped a mathematical model for the multi-objective minimum cost flow problem, applied in networks with varyingattributes on arcs. The model finds the set of non-dominated solutions for a multi-objective stochastic network havingvariations in attributes of its arcs and nodes, such as cost or transportation time. A modified version of the two-stagemethod was used to address the stochastic nature of the problem combined with the epsilon-constraint method, whichis used for building the set of non-dominated solutions.This paper presents the main features of the model, the theoretical bases and a computational implementation.Experiments were applied in a transport network for the exportation market of ornamental flowers as perishable goodsfrom Mexico to the United States, which considered variations in border crossing times.

This paper uses System Dynamics modeling and process simulation to explore coordination in two logistic processes(procurement and production) of the supply chain of an ethanol plant. In that sense, three production scenarios areevaluated to identify: a) stock movement according to current inventory policies, and b) the critical variables affectingthe coordination for these two processes. Since the main goal in the company is to meet customer demand, thisresearch incorporates sales forecasting, and four performance indicators to evaluate the state of the processes: 1)average percentage of demand satisfaction, 2) maximum amount of ethanol in excess, 3) available ethanol at the endof the year, and 4) inventory costs. To model the case study, the change in production yield and specific constraintsfor the chain are considered. The simulation results show that System Dynamics modeling can be used to observe theeffects of policies on inventory, and meeting the demand in a real system. It also can define the coordination for asupply chain and give information to improve it. The developed model uses STELLA® software to simulate the logisticprocesses and execute the evaluation employing the performance indicators.

Nowadays, Supply Chain success and competitiveness heavily depend on the integration of its components andadaptability to deal with a changing environment. This article suggests the integration of design and management of aSupply Chain from an outcome-driven perspective. We propose a two-phase decision-making support methodology:first suppliers are pre-screened by solving a multi criteria sorting problem, and then a design and management plan isgenerated by solving a Mixed Integer Linear Programming Model. Experimentally we showed that the proposedmethodology can efficiently solve to optimality the most popular benchmark instances published in previous papermoreover our model also includes problem characteristics that have not been addressed together in previouspublished papers.

In this paper we show the importance of applying mathematical optimization when designing the distribution networkin a supply chain, specifically in making decisions related location of facilities and inventory management, which areassociated with different levels of planning but are closely related.The addressed problem is an extension of the classic capacitated facility location problem. The distinguishing featuresare: the inventory management, the presence of multiple plants, and the single source constraints in both echelons. Akey issue is that demand at each distribution center is a function of the demands at the retailers assigned, which is arandom variable whose value is not known at the time of designing the network. We focus on the mathematicalmodeling of the problem and the evaluation of the performance of the developed models, so, it can be observed thetroubles that arise when modeling supply chains that consider different types of decisions.

This paper aims at examining the commercial vehicle operators’ value of delay (VOD) due to highway congestion inurban area. The VOD is a fundamental parameter that influences the private sector’s response to public freightprojects and policies. This paper adopts two methods to estimate the VOD; one being the stated preference (SP)survey and the other being simulation of a carrier’s fleet operations. The former applies a Logit model and estimates adriver perceived VOD as $56.48 per vehicle per hour for the regular short-haul delivers. The latter gauges theeconomic impact of delay on carrier’s fleet operations in the Houston highway network. The operations essentiallyreflect more of a just-in-time system due to the rather stringent time window constraints. The simulation is conductedon a rolling time horizon with a heuristic algorithm for dispatching trucks. The major findings include, but are notlimited to as follows. The drivers paid by miles perceive a significantly higher VOD than the others; the drivers aremore willing to pay for a faster trip when the toll charges do not come out of their own pockets; VOD increases withuncertainty and demand for capacity. The comparison between the survey and the simulation results also indicatesthat the interviewed drivers perceive a significantly lower VOD than they may actually experience as a fleet, anindicator of myopic vision.

A problem of packing a limited number of unequal circles in a fixed size rectangular container is considered. The aimis to maximize the (weighted) number of circles placed into the container or minimize the waste. This problem hasnumerous applications in logistics, including production and packing for the textile, apparel, naval, automobile,aerospace and food industries. Frequently the problem is formulated as a nonconvex continuous optimization problemwhich is solved by heuristic techniques combined with the local search procedures. A new formulation is proposedbased on using a regular grid approximated the container and considering the nodes of the grid as potential positionsfor assigning centers of the circles. The packing problem is then stated as a large scale linear 0-1 optimizationproblem. The binary variables represent the assignment of centers to the nodes of the grid. The resulting binaryproblem is then solved by the commercial software. Two families of valid inequalities are proposed to strengtheningthe formulation. Nesting circles inside one another is also considered. Numerical results are presented to demonstratethe efficiency of the proposed approach.

To understand disruptions and their propagation along the supply chains is becoming critical for designing competitiveglobal supply chains operating in emerging economies. It leads to economic damages to every organization involvedin a supply chain, but it also decreases national logistics competitiveness. This research provides numerical elementsin terms of significance of the security issue in Latin America, and at the same time, proposes a system dynamicsassessment model based on real-life information, able to establish analysis scenarios in order to measure the impactsderived of supply chain disruptions propagation caused by criminal acts. Finally, useful conclusions for designingmore resilient supply chains and future research are exposed.

Describe the interoceanic Mazatlan-Houston Logistic Corridor (MHLC) as an alternative route to create sustainablecompetitive advantages for Mexican, USA, and international firms competing in an international marketplace. Takinginto account the competitive advantages of utilizing this corridor for international trade, we analyze supply chainstrategies for Mexican and international companies demanding economical logistic solutions in this region. It wasfound that the MHLC benefits efficient industry segments with demand well known in advance. It was also found thatthe potential of both inbound and outbound container traffic to the Asia-Pacific marketplace along this internationalcommerce corridor fluctuates between 39,000 and 761,000 TEU´s.