| 1. |
- Axsäter, Sven, et al.
(author)
-
Evaluation of a new type of sequential lot sizing techniques
- 1990
-
In: Engineering Costs and Production Economics. - 0167-188X .- 1878-4011. ; 19:1-3, s. 281-286
-
Journal article (peer-reviewed)abstract
- The classical dynamic lot size problem without backlogging is usually solved with the aid of various heuristics. Most heuristics are sequential, i.e. the demand is considered period for period, and a decision whether to include the demand in a certain period in the preceding batch is taken without regarding the future demand. Recently, it has been shown how to design a sequential lot sizing rule that will optimize the average performance, provided that a typical demand looks like a sequence of independent and identically distributed random numbers. The purpose of this paper is to evaluate if and how this methodology can be implemented in practice. The new lot sizing techniques are evaluated in a simulation study for different types of demand.
|
|
| 2. |
- Billberg, Ingmar, 1946-2005
(author)
-
Prestigefyllt broprojekt
- 1991
-
In: Kulturmiljövård. - Stockholm : Riksantikvarieämbetet. - 1100-4800. ; [16]:2, s. 55-56
-
Journal article (pop. science, debate, etc.)
|
|
| 3. |
- Ljungberg, Anders
(author)
-
Measurement systems and process orientation with focus on the order process
- 1998
-
Doctoral thesis (other academic/artistic)abstract
- The inability of organisations to develop successfully and their lack of a holistic view and of relevant quantitative facts are factors that played a major role in my choice of a research area for this and my licentiate thesis (Ljungberg, 1994). These two theses together represent the work conducted for the PhD degree. There is a strong need in this research area for increased insight into the development of process-oriented measurement systems for analysing the order process, as well as into the prerequisites for this and the potential gains the development of such systems represents. Use has been made here of a systems approach together with elements of an actor-based approach. The boundary-crossing character of the research area required an interdisciplinary integration of knowledge. The research process included an extensive study of the literature, a major case study carried out in the form of action research, and a field study. Earlier work resulted in the Measurement System Development model, describing in seven steps how a measurement system can be developed. The step selection and derivation of measures had been found to call for further research. A two-part solution was developed: a method for the selection and derivation of measures, taking as its starting point a second part, a Process Measure Classification model. The company VOAC Hydraulics' desire to develop a measurement system for their order process represented the starting point of the case study. A project group containing representatives of the order process was created. Originally an isolated project, it came to gradually be related to a considerable number of strategic issues. It resulted in a preliminary measurement system, yielded new insights into the order process, and helped the team members develop an interest in processes and an understanding of them. Parallel to the project, increasing attention was directed at process thinking. A major reorganisation was carried out, transforming the organisation in the direction of being more process-oriented. The process-related work increased continually, leading to the speed of change being rather low, at the same time as the range of changes made was extensive. VOAC's suddenly being sold, however, meant a serious setback for the process orientation. Although further attempts at this were made, the results were limited. The case illustrates how significant momentum can be lost. The results of the research yield a framework for the development of process-oriented measurement systems and serve to clarify issues regarding both process measurement and process-oriented organisations. The major strength of the study can be seen in its providing for both of these parts and combining them so as to provide a holistic view of the development of measurement systems. Further research appears called for within such areas as: how to provide proper input to the Measurement System Development model, how to distinguish between different types of demands placed on a process, and development of the process of developing processes. (Ljungberg, A.: Measurement of service and quality in the order process. Department of Engineering Logistics, Lund University, 1994.)
|
|
| 4. |
- Näslund, Dag
(author)
-
Towards Bridging the Gap Between Strategy and Operations - A Process Based Framework
- 1999
-
Doctoral thesis (other academic/artistic)abstract
- This dissertation is about bridging the gap between strategy and operations in organizations. To bridge that gap, processes are viewed not only from an operational perspective but also from conceptual, as well as a hierarchical perspectives. Bridging the gap can furthermore make organizational change initiatives more logical, and simplify the development and usage of needed performance measurement systems. This research is based on previous research (Näslund, 1996) which indicated that the lack of connection to strategy is a common problem for change initiatives as well as for operations and efforts to develop and implement performance measurement systems. There seems to be a lack of connection between: * Strategy * Operations * Change Initiatives * Performance Measurement Systems A result is the description of a framework in which I identify three different roles for processes: * To connect the components of strategy, operations, change initiatives and performance measurement systems - a conceptual perspective. * To bridge the gap between strategy and operations at the tactical level of organizations by facilitating the translation of strategic goals into process goals and then operational goals - a hierarchical perspective. * To be a model to both represent the sequence of activities in a flowchart, and a (human activity) system - a traditional, operational perspective. The research is applied, and theoretically based on systems theory and logistics. Methodologically, the research is primarily qualitative. The research approach, a combination of the systems approach and action research, can be characterized as broad and multi-disciplinary. The framework establishes a conceptual relationship between the components of strategy, operations, change initiatives and performance measurement systems, and it explains how the components can be connected with processes. The framework also describes how the most important processes - the tactical level - can bridge the gap between strategic and operational levels of organizations.
|
|
| 5. |
- Patel, Poorvi
(author)
-
Nonlinear Creep Model of Paper and Corrugated Board Materials
- 1999
-
Doctoral thesis (other academic/artistic)abstract
- Models of the nonlinear creep behavior of paper, and of the global buckling , local buckling and creep buckling of corrugated board have been developed. The studies of creep and buckling were limited to climate conditions with constant relative humidity. First the short-term elastic buckling of corrugated board panels was studied. Then an appropriate creep equation, based on the Schapery representation, for liner and fluting materials was developed and implemented in a finite element code to study creep buckling and time to failure of a corrugated board panel axially loaded in compression. Experimental tensile creep-recovery tests of 300 g/m2 kraftliner (used for the facing of corrugated boards) and 150 g/m2 semi-chemical testliner (used for the fluting) at 50, 70 and 90%RH were made by a special designed tensile creep tester. Compression creep-recovery tests at 50%RH was made using a compression creep tester developed at STFI. For the short-term loading case, the experimental global buckling and postbuckling deformation performance of a corrugated board panel was found to be in good agreement with the performance predicted by FE-calculation. The calculated local buckling load was however almost 2.5 times higher than the experimentally observed local buckling load in the panel. This discrepancy between the experimental and calculated local buckling load was most probably due to development of global buckling before local buckling of the panel. For the long-term loading case, the Schapery equation was found to give a good representation of the creep behavior of the facing and fluting material and enabled reasonably accurate predictions of the creep behavior of corrugated board. The Schapery representation for paper was implemented in the finite element codes Ansys and Abaqus. In Ansys, the Schapery representation was described by using stress-strain isochrounes and failure of the material was considered by using a Tsai-Wu failure criterion based on a time independent failure strain in the CD and MD at each layer. This model with isochrounes and a material failure criterion was found to be suitable for calculating failure load for a given time to failure. In the calculations made by the finite element code Abaqus no simplification was made of the Schapery representation and no material failure criterion was used. This model is more accurate than the model with isochrounes stress-strain curves in the sense that the influence of stress redistribution on the creep is considered. The model is therefore suitable to study the creep strains of a corrugated board structure as function of time, both the in-plane strains and pre-failure out-of-plane displacements. The creep buckling analysis was verified by tests. It was found that the experimental out-of-plane displacement of the mid-node of a panel under compression load was in good agreement with the calculated out-of-plane displacement.
|
|
| 6. |
|
|
| 7. |
-
VTI:s och TFB:s forskardagar : del 2
- 1993
-
Editorial proceedings (other academic/artistic)abstract
- Rapportsammanställning av föredrag vid forskardagarna 1993-01-11--12 beträffande:geoteknik inom transportsektorntransporterna i ett framtida EGden internationella och svenska flygmarknaden inför framtidenkan sjöfarten stärka sin ställning som ett transport- och miljövänligt alternativ till andra transportslag?förbättrad säkerhet med hjälp av informationsteknologi (RTI) och annan modern teknikRTI på svenska vägarutveckling av kostnadseffektiva material/transportflödennationella trafikprognoserforskningsinformation i förändringinfrastrukturen och dess betydelse för samhället
|
|
| 8. |
- Axsäter, Sven
(author)
-
An Inventory Model with Lateral Transshipments
- 1991
-
In: Modern production concepts. - Berlin : Encyclopedia of Global Archaeology/Springer Verlag. - 0387536434 ; , s. 345-52, s. 345-352
-
Conference paper (peer-reviewed)
|
|
| 9. |
- Axsäter, Sven, et al.
(author)
-
Approximating general multi-echelon inventory systems by Poisson models
- 1994
-
In: International Journal of Production Economics. - : Elsevier BV. - 0925-5273 .- 1873-7579. ; 35:1-3, s. 201-206
-
Journal article (peer-reviewed)abstract
- We consider a continuous review two-level inventory system with a central warehouse and a number of retailers. The demand processes at the retailers are different compound Poisson processes. We present and evaluate an approximate optimization technique, where the real demand is replaced by "equivalent" Poisson demand such that the ratio between mean and standard deviation is the same as for the real distribution. The solution of the Poisson model is then scaled back to the original problem.
|
|
| 10. |
- Axsäter, Sven, et al.
(author)
-
Comparison of Echelon Stock and Installation Stock Policies for Two-Level Inventory Systems
- 1996
-
In: International Journal of Production Economics. - : Elsevier BV. - 0925-5273 .- 1873-7579. ; 45:1-3, s. 303-310
-
Journal article (peer-reviewed)abstract
- It is previously known that echelon stock reorder point policies dominate installation stock reorder point policies for serial and assembly multi-level inventory systems. This paper presents worst-case results for the relative cost difference in case of constant demand and no backorders. Furthermore, we analyze distribution systems with stochastic demand by simulation. Depending on the structure of the system either echelon stock or installation stock policies may be advantageous.
|
|
