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All Journal Makara Journal of Technology
Katsuhiko Takahashi, Katsuhiko
Departement of System Cybernetics, Faculty of Engineering, Hiroshima University, Hiroshima 739-8527, Japan
Chemical Engineering, Chemistry & Bioengineering Civil Engineering, Building, Construction & Architecture Electrical & Electronics Engineering Engineering Materials Science & Nanotechnology Mechanical Engineering

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Multi-Project Scheduling Cost Optimization in a Machine Manufacturer Engineer-to-Order Farizal, Farizal; Rachman, Amar; Tandean, Tifani; Sudarto, Sumarsono; Takahashi, Katsuhiko
Makara Journal of Technology Vol. 20, No. 1
Publisher : UI Scholars Hub

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Abstract

This paper discusses the utilization of mixed integer linear programming (MILP) model to optimize cost for multiproject scheduling in a machine maker company. The objective is to minimize total project’s penalty cost and labor cost. The model formulated shows how to achieve the objective i.e. whether to use outsourcing or overtime to finish all projects. The model of multi-project scheduling was solved by Branch & Bound algorithm coded in Lingo 14.0 software. The case study shows that if a company wants to minimize lateness, it should use overtime instead of outsourcing, which minimize total lateness of projects by 144 days or 73.5%. Whereas, if a company wants to optimize cost, they should use outsourcing instead of overtime, which reduces total cost of about 10,873,000 IDR or 28.5%. These results indicate that the model developed is applicable for optimizing multi-project scheduling.
Challenges in Optimization for the Performance on Sustainability Dimensions in Reverse Logistics Social Responsibility Sudarto, Sumarsono; Takahashi, Katsuhiko; Dewo, Mochammad
Makara Journal of Technology Vol. 27, No. 2
Publisher : UI Scholars Hub

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Reverse logistics social responsibility is preferred as the most acceptable solution for addressing the challenges in stakeholders’ debate regarding social responsibility in supply chains because it involves as many actors as possible in the supply chain to perform social responsibility to achieve sustainability. This paper explores the challenges in achieving optimal policies in sustainability dimensions for collection and recycling facilities in reverse logistics. Sustainability dimensions include economic, environmental, and social aspects. The reverse logistics is modeled on System Dynamics, and a simplified statistical analysis using a contour chart is employed in numerical experiments. Results show a narrow area of optimal solutions in contour charts for policy parameter settings to realize sustainability. Therefore, this paper finds that optimization of reverse logistics to develop sustainability is a highly challenging task for policy makers. Therefore, managers must carefully study their policies before implementation to avoid unnecessary and less optimal performance in the sustainability dimensions.
Co-Authors Amar Rachman Dewo, Mochammad Farizal Farizal Sumarsono Sudarto, Sumarsono Tifani Tandean, Tifani