Profit-oriented disassembly-line balancing

As product and material recovery has gained importance, disassembly volumes have increased, justifying construction of disassembly lines similar to assembly lines. Recent research on disassembly lines has focused on complete disassembly. Unlike assembly, the current industry practice involves partial disassembly with profit-maximization or cost-minimization objectives. Another difference between assembly and disassembly is that disassembly involves additional precedence relations among tasks due to processing alternatives or physical restrictions. In this study, we define and solve the profit-oriented partial disassembly-line balancing problem. We first characterize different types of precedence relations in disassembly and propose a new representation scheme that encompasses all these types. We then develop the first mixed integer programming formulation for the partial disassembly-line balancing problem, which simultaneously determines (1) the parts whose demand is to be fulfilled to generate revenue, (2) the tasks that will release the selected parts under task and station costs, (3) the number of stations that will be opened, (4) the cycle time, and (5) the balance of the disassembly line, i.e. the feasible assignment of selected tasks to stations such that various types of precedence relations are satisfied. We propose a lower and upper-bounding scheme based on linear programming relaxation of the formulation. Computational results show that our approach provides near optimal solutions for small problems and is capable of solving larger problems with up to 320 disassembly tasks in reasonable time

Reliabilität - die Genauigkeit einer Messung (Version 1.1)

Die Reliabilität beschreibt die Genauigkeit einer Messung. In diesem Beitrag wird das Konzept Reliabilität definiert und es wird erläutert, warum die Reliabilität einer Messung relevant ist. Danach wird diskutiert, welche Modellannahmen getroffen werden müssen, um die Reliabilität einer Messung zu schätzen und es werden fünf Methoden zum Schätzen der Reliabilität vorgestellt: die Re-Test Korrelation, die Parallel-Test Korrelation, die Split-Half Korrelation, die interne Konsistenz und das Schätzen der Reliabilität mit Strukturgleichungsmodellen. Abschließend wird in knapper Form auf Gemeinsamkeiten und Unterschiede der klassischen Testtheorie und der Item-Response Theorie und deren Bedeutung für die Schätzung der Reliabilität eingegangen