Lagrangian Formulation for Energy-efficient Warehouse Design

Energy consumption in modern warehouses is today an important issue which has not received much attention in the scientific community. In this paper it is addressed the problem of warehouse design considering the energy costs incurred by vehicles and equipment in a fully or partially automated facility. Closed-form solutions are obtained by a formulating the Lagrangian of an operational cost function with equality constraints. The contribution of the paper is to develop formulas for reduced energy consumption and pollution, both relevant aspects in sustainable engineering systems. An example applied to a distributor of MRO items is presented. In this version the energy cost is integrated into the formula, modifying the method presented in [1]

Accelerating the B&B algorithm for integer programming based on flatness information: an approach applied to the multidimensional knapsack problem

This paper presents a new branching rule based on the flatness of a polyhedron associated to the set of constraints in an integer linear programming problem. The rule called Flatness II is a heuristic technique used with the branch-and-bound method. The rule is concerned with the minimum integer width vector. Empirical evidence supports the conjecture that the direction with the highest value of the vector’s components indicates a suitable branching direction. The paper provides theoretical results demonstrating that the columns of the matrix A corresponding to a set of constraints Ax≤b may be used to estimate the minimum integer width vector; this fact is used for constructing a new version of the branching rule as was reported in a previous paper by the authors. In addition, the new rule uses a branching direction that chooses the child node closest to the integer value (either up or down). Thus, it uses a variable rule for descending the tree. Every time a new sub-problem is solved, the list of remaining unsolved sub-problems is analyzed, with priority given to those problems with a minimum objective function value estimate. The conclusions of the work are based on knapsack problems from the knapsack OR-Library. From the results, it is concluded that the new rule Flatness II presents low execution times and minimal number of nodes generated

Multicriteria Supplier Classification for DSS: Comparative Analysis of Two Methods

In this paper the analysis of two multicriteria decision making (MCDM) methods for sorting suppliers in industrial environments is presented. The MCDM methods correspond to Electre and FlowSort and both are applied to the classification of providers in an actual case of the local softdrink bottling industry in Chile. The results show that Electre as an outranking method it may well classify suppliers in a similar manner as FlowSort does. Nevertheless, due to the intrinsic underlying fuzzy multicriteria nature of the problem, FlowSort is found to be more suitable method for building a rule-based system based on preference functions for automating the process of suppliers clustering when developing strategies of relationship management in the sense of the Kraljic categories in supply chain management

Improving the productivity of the copper mining process in the Chilean copper industry

This paper presents a linear programming model used for decision making in the mining process of copper concentration from sulphide minerals. The developed model enables the decision maker to select the types of ore to be used in the mix to maximize the metallurgical recovery and the copper grade at the end of the process. The model is of the mixture model of minerals with added economic variables such as processing costs, electric power and others. The process has four sub-processes that are crushing the ore, crushing the crushed ore, flotation of the ground ore to obtain copper concentrate and drying, in which the water is extracted. The model uses a set of variables whose size varies according to the number of lots of minerals and the number of planning days considered. The model may be considered a considerable problem when a long period of time is planned, but has only been implemented with 3.000 variables and 2.000 constraints. The developed model is being implemented in the National mining company, which buys ore from small producers to produce copper concentrate and then melt and refine it to obtain high grade copper. The generated model produces savings of the order of thousand dollars per day, when compared to the current methods of allocating minerals, which represents millions of dollars per year. It also produces a benefit due to the fact that lower operating costs are obtained, with estimate savings of the order of 5% of the current cost.</p

Assessment of steady and unsteady friction models in the draining processes of hydraulic installations

The study of draining processes without admitting air has been conducted using only steady friction formulations in the implementation of governing equations. However, this hydraulic event involves transitions from laminar to turbulent flow, and vice versa, because of the changes in water velocity. In this sense, this research improves the current mathematical model considering unsteady friction models. An experimental facility composed by a 4.36 m long methacrylate pipe was configured, and measurements of air pocket pressure oscillations were recorded. The mathematical model was performed using steady and unsteady friction models. Comparisons between measured and computed air pocket pressure patterns indicated that unsteady friction models slightly improve the results compared to steady friction models

Assessment of Steady and Unsteady Friction Models in the Draining Processes of Hydraulic Installations

The study of draining processes without admitting air has been conducted using only steady friction formulations in the implementation of governing equations. However, this hydraulic event involves transitions from laminar to turbulent flow, and vice versa, because of the changes in water velocity. In this sense, this research improves the current mathematical model considering unsteady friction models. An experimental facility composed by a 4.36 m long methacrylate pipe was configured, and measurements of air pocket pressure oscillations were recorded. The mathematical model was performed using steady and unsteady friction models. Comparisons between measured and computed air pocket pressure patterns indicated that unsteady friction models slightly improve the results compared to steady friction models

Optimization of Port Layout to Determine Greenhouse Gas Emission Gaps

Ports are of great strategic importance for a country. Nowadays, compliance with environmental requirements is required, forcing the migration towards clean energies. Therefore, it is necessary for emerging ports, as those in developed countries, to incorporate in their policies the use of electric power in the machinery that moves containers in the terminals. To learn how the problem is addressed in other countries, an extensive bibliographic review is presented. Then, the energy policies and criteria of a group of ports in an emerging country and a European port are studied. Subsequently, in order to determine the gaps between the ports investigated, the layout of the cargo yard of each of the terminals is optimized; the emissions of Carbon Dioxide (CO2) and other Greenhouse Gases (GHG) gases are calculated; and finally, the decrease in emissions when switching from diesel to electricity is estimated. The strategic and operational gaps related to energy management between the emerging and developed countries are discussed. It is concluded that research is needed to investigate how these initiatives impact the city and improve other sustainable aspects

Circular Economy 4.0 Evaluation Model for Urban Road Infrastructure Projects, CIROAD

This paper provides a multicriteria evaluation model, based on the AHP methodology for the evaluation of the Circular Economy 4.0’s, which develops the metric called “Circularity indicator for urban road projects (CIROAD)”. The main contribution of this work is to provide a measurement scale specifically designed for urban road infrastructure projects. It is a useful tool to assess the degree of implementation of the principles of the Circular Economy (CE) and the Fourth Industrial Revolution (I4.0) in an integrated manner in these types of projects, generating valuable information for all stakeholders and contributing to the objective of accelerating the transition towards a Circular Economy 4.0 model in the construction industry. The model is defined with twenty-five sub-criteria and seven general criteria, which are: (1) Circular Materials; (2) Circular Design Approaches; (3) Circular Construction Approaches; (4) Circular Operation Approaches; (5) Approaches to Deconstruction and Resource Recovery; (6) Social Value Creation; and (7) Economic Performance. The developed CIROAD model was applied to three projects in the urban transport area of the Chilean Ministry of Housing and Urbanism (MINVU/SERVIU) in the Santiago Metropolitan Region (RM). In these three projects, low performance was observed in terms of CIROAD scores (between 21% and 28% of a maximum of 100%); that is, there is a significant opportunity for improvement by incorporating more circular practices in the development of projects by the studied organization. To accelerate the transition to a circular economy model in the development of its projects, it is proposed that the organization prioritize improving the following circular practices (in order of importance): (1) the design of pavements with environmental criteria; (2) preserving value; (3) conducting cost–benefit analysis (CBA) of waste management; (4) environmental declaration of materials (EPD); (5) the used of recycled materials; and (6) BIM-based design. Finally, the suggestion for the organization in charge of these projects is to use the developed CIROAD model as a tool to support decision making regarding the prioritization of its project portfolio. That is, the organization should use CIROAD to generate a ranking score for each project and allocate resources for investment in the initiatives that show the best circularity performances, as estimated by CIROAD

Location of the Intermediate Echelon to Add Purchase Value and Sustainability Criteria in a Mining Supply Network

This study presents an operational analysis to determine the location of an intermediate hub in a supply network for the mining industry, incorporating sustainability criteria through an optimization model. The sector of small, medium, and artisan mining enterprises (PAMMA), in Chile, has the same pressure as large mining to meet the demands of sustainability in the medium term, but the network of PAMMA facilities is precarious and requires government support for development. One strategy to improve the supply network is to locate intermediate points with limited capacities (called purchasing powers) to help the viability of the business model by incorporating sustainability objectives, such as diminishing the movement of minerals, as well as reducing the carbon footprint and gas emissions, all in support the promotion of the activity of small miners. In order to achieve the strategy above, a mathematical model of location and sustainable capacity is proposed. A grouping of suppliers was carried out to establish the number of mining suppliers in each cluster and the location of the intermediate hubs. Then, the prioritization of the parameters and classification of the processing plant alternatives was performed to define a vector of weights to rank the degree of sustainability. A sustainability matrix was calculated on the basis of the distances and transportation costs between the supplier hubs of the supply network and the processing plants. With each of these factors, a capacity model was developed to validate the mineral process flows in the supply network and estimate the expected productivity levels. The model is intended to support operational decision making when determining the location of an intermediate purchasing power that reduces the impact of transportation costs and emissions. The model was applied in a case study of the supply network in the small mining sector in Chile. The results recommend the location of hubs to add value and encourage investment in the PAMMA supply network