Browsing by Subject "Process engineering"

Now showing 1 - 7 of 7

Open Access
Automated web services composition with the event calculus
(Springer, 2007-10) Aydın, Onur; Kesim-Çiçekli, Nihan; Çiçekli, İlyas
As the web services proliferate and complicate it is becoming an overwhelming job to manually prepare the web service compositions which describe the communication and integration between web services. This paper analyzes the usage of the Event Calculus, which is one of the logical action-effect definition languages, for the automated preparation and execution of web service compositions. In this context, abductive planning capabilities of the Event Calculus are utilized. It is shown that composite process definitions in OWL-S can be translated into Event Calculus axioms so that planning with generic process definitions is possible within this framework. © 2008 Springer-Verlag Berlin Heidelberg.
Open Access
Conceptual model for an ICT-enabled educational platform for collaborative design
(CRC Press/Balkema, 2015) Şenyapılı, Burcu; Anumba, C.J.
Almost all design related practices (architecture, architectural engineering, interior architecture/design, landscape architecture, urban design, industrial design, fashion and visual communication design) heavily depend on collaboration between colleagues from the same or different disciplines. However, practitioners who collaborate in practice, seldom have the opportunity to collaborate during design education. Having the opportunity to collaborate on educational design projects and acquiring collaboration skills and experience during design education should contribute to the quality and efficiency of future professional collaborations. Recent advancements in information and communication technologies have enabled collaboration during the process of the design studio, especially between geographically dispersed parties, but initiating and establishing such collaboration opportunities depends on the parties' singular efforts. This paper reviews previous and ongoing efforts at introducing multi-disciplinary collaborative design studios in Turkey and the USA and proposes a conceptual model for an online collaboration network that aims at promoting and facilitating collaboration among design schools and design instructors/students/ researchers. The network, establishing an educational platform for collaborative design (EPCOD) is intended to comprise a digital pool of design projects, enabling potentials of design collaboration for students from the same or different disciplines. It is designed to be accessible to all design schools all over the world, forming a specific and rich platform for design education. The role of current and emerging information and communication technologies in facilitating the proposed network-based collaboration is also discussed. © 2015 Taylor & Francis Group.
Open Access
Dynamic lot sizing problem for a warm/cold process
(Taylor & Francis, 2006) Toy, A. Ö.; Berk, E.
We consider a dynamic lot sizing problem with finite capacity for a process that can be kept warm until the next production period at a unit variable cost ωt only if more than a threshold value has been produced and is cold, otherwise. That is, the setup cost in period t is Kt if xt-1 < Qt-1 and kt, otherwise (0 ≤ kt ≤ Kt). We develop a dynamic programming formulation of the problem, establish theoretical results on the structure of the optimal production plan and discuss its computational complexity in the presence of Wagner-Whitin-type cost structures. Based on our stuctural results, we present an optimal polynomial-time solution algorithm for kt = 0, and also show that an optimal linear-time solution algorithm exists for a special case. Our numerical study indicates that utilizing the undertime option (i.e., keeping the process warm via reduced production rates) results in significant cost savings, which has managerial implications for capacity planning and selection.
Open Access
Economic design of EWMA control charts based on loss function
(Elsevier, 2009) Serel, D. A.
For monitoring the stability of a process, various control charts based on exponentially weighted moving average (EWMA) statistics have been proposed in the literature. We study the economic design of EWMA-based mean and dispersion charts when a linear, quadratic, or exponential loss function is used for computing the costs arising from poor quality. The chart parameters (sample size, sampling interval, control limits and smoothing constant) minimizing the overall cost of the control scheme are determined via computational methods. Using numerical examples, we compare the performances of the EWMA charts with Shewhart over(X, -) and S charts, and investigate the sensitivity of the chart parameters to changes in process parameters and loss functions. Numerical results imply that rather than sample size or control limits, the users need to adjust the sampling interval in response to changes in the cost of poor quality.
Open Access
An integrated process planning approach for CNC machine tools
(Springer-Verlag, 1996) Aktürk, M. S.; Avcı, S.
In view of the high investment and tooling cost of a CNC machining centre, the cutting and idle times should be optimised by considering the tool consumption and the non-machining time cost components. In this paper, we propose a detailed mathematical model for the operation of a CNC machine tool which includes the system characterisation, the cutting conditions and tool life relationship, and related constraints. This new module will be a part of an overall computer-aided process planning system to improve the system effectiveness and to provide consistent process plans. A hierarchical approach is presented for finding tool-operation assignments, machining conditions, appropriate tool magazine organisation and an operations sequence which results in the minimum production cost. © 1996 Springer-Verlag London Limited.
Open Access
Investing in quality under autonomous and induced learning
(Taylor & Francis, 2003) Serel, D. A.; Dada, M.; Moskowitz, H.; Plante, R. D.
The reduction of variability in product performance characteristics is an important focus of quality improvement programs. Learning is intrinsically linked to process improvement and can assume two forms: (i) autonomous learning; and (ii) induced learning. The former is experientially-based, while the latter is a result of deliberate managerial action. Our involvement in quality and capacity planning with several major corporations in different industries suggested that it would be instructive to devise a model that would prescribe an optimal combination of autonomous and induced learning over time to maximize process improvement. We thus propose such a model to investigate the optimal quality improvement path for a company given that quality costs depend on both autonomous and induced types of learning experienced on a number of quality characteristics. Several properties of an optimal investment path are developed for this problem. For example, it is shown that decisions maximizing short-term gains may actually lead to suboptimal resource utilization decisions when total costs associated with a longer planning horizon are taken into account. Numerical examples are used to assess the sensitivity of the optimal investment plan with respect to changes in several model parameters.
Open Access
Scheduling with tool changes to minimize total completion time: a study of heuristics and their performance
(John Wiley & Sons, Inc., 2003) Aktürk, M. S.; Ghosh, J. B.; Güneş, E. D.
The machine scheduling literature does not consider the issue of tool change. The parallel literature on tool management addresses this issue but assumes that the change is due only to part mix. In practice, however, a tool change is caused most frequently by tool wear. That is why we consider here the problem of scheduling a set of jobs on a single CNC machine where the cutting tool is subject to wear; our objective is to minimize the total completion time. We first describe the problem and discuss its peculiarities. After briefly reviewing available theoretical results, we then go on to provide a mixed 0–1 linear programming model for the exact solution of the problem; this is useful in solving problem instances with up to 20 jobs and has been used in our computational study. As our main contribution, we next propose a number of heuristic algorithms based on simple dispatch rules and generic search. We then discuss the results of a computational study where the performance of the various heuristics is tested; we note that the well-known SPT rule remains good when the tool change time is small but deteriorates as this time increases and further that the proposed algorithms promise significant improvement over the SPT rule.