Surrogate-based optimization of a periodic rescheduling algorithm

Periodic rescheduling is an iterative method for real-time decision-making on industrial process operations. The design of such methods involves high-level when-to-schedule and how-to-schedule decisions, the optimal choices of which depend on the operating environment. The evaluation of the choices typically requires computationally costly simulation of the process, which—if not sufficiently efficient—may result in a failure to deploy the system in practice. We propose the continuous control parameter choices, such as the re-optimization frequency and horizon length, to be determined using surrogate-based optimization. We demonstrate the method on real-time rebalancing of a bike sharing system. Our results on three test cases indicate that the method is useful in reducing the computational cost of optimizing an online algorithm in comparison to the full factorial sampling.     

Ion-implanted capacitively coupled silicon strip detectors with integrated polysilicon bias resistors processed on a 100 mm wafer

Double-sided silicon strip detectors with integrated coupling capacitors and polysilicon resistors have been processed on a 100 mm wafer. A detector with an active area of 19 × 19 mm² was connected to LSI readout electronics and tested. The strip pitch of the detector is 25 μm on the p-side and 50 μm on the n-side. The readout pitch is 50 μm on both sides. The number of readout strips is 774 and the total number of strips is 1161. On the p-side a signal-to-noise of 35 has been measured using a ⁹⁰Sr β-source. The n-side has been studied using a laser.     

Dynamic models and fault diagnosis‐based triggers for closed‐loop scheduling

Establishing an explicit feedback connection between production management and process control decisions is a key requirement for more nimble and cost effective process operations in today's variable market conditions. Past research efforts focused on embedding dynamic process information in the production scheduling problem. In this article, we propose a novel framework for closing the scheduling loop, based on considering the process‐level events and disturbances that impact the implementation of scheduling decisions. We emphasize the role of a comprehensive fault detection, isolation and reconstruction mechanism as a trigger for rescheduling decisions and for reflecting the process capabilities altered by these events in the rescheduling problem formulation. Our framework is agnostic to the process type, and we present two (continuous process, sequential batch process) case studies to demonstrate its applicability. © 2016 American Institute of Chemical Engineers AIChE J, 63: 1959–1973, 2017     

Integration of scheduling and control—Theory or practice?

Today's industries are more than ever forced to lower their operational costs, especially during the ongoing economic recession where the whole existence of many businesses is endangered. This has created a need of increased information sharing between various decision-support systems. The target is to have full transparency and ensure that the overall result of individual optimization tasks is “globally optimal”, i.e., that the decisions taken on different levels do not negate each other. This leads inevitably to more complex optimization systems as the models tend to cover larger problem entities in order to merge previously separated optimization targets or include earlier not considered aspects in order to avoid getting stuck into unfavorable local optima. Another complexity arises from the need of communication between the tasks—earlier isolated problems become networked, which means that the definition of optimization goals cannot be derived from local facts alone. This paper discusses some issues emerging from the integration of production scheduling and control. Some existing standards to support the integration challenge are presented, followed by an overview of recent research results. An interesting question is to what extent such an integration activity is the task of a scientist or a practitioner? The paper concludes by highlighting important open questions and raises some remaining challenges for the future.     

Ubimedia based on readable and writable memory tags

Ubimedia is a concept where media files are embedded in everyday objects and the environment. We propose an approach where the user can read and write these files with his/her personal mobile phone simply by touching the physical objects. This facilitates easy access and storage of, e.g. video and audio files related to the physical object in question. This paper describes our work in developing a technical solution for ubimedia and studying user acceptance of forthcoming ubimedia services. Our technical development of the ubimedia concept has been focused on a mobile phone platform with a tag reader/writer, memory tags with large storage capacity, and the communication between the phone and the tags. Currently, the technical design is in test and evaluation phase. The preliminary results show that the concept works and it can be implemented technically. In parallel with the technical development, we have studied usage possibilities for ubimedia and user acceptance of future ubimedia services. User acceptance has been studied in a web survey and in user evaluations of proofs-of-concept. In addition, an ethical assessment has been carried out. The users appreciated especially the simplicity, speed, low cost and reliability of ubimedia. Ethical concerns were related to control over the download with regard to viruses and other unwanted content.     

On identifying codes in the hexagonal mesh

It is shown that, if r?2, there exists an (r,?2)-identifying code in the infinite hexagonal mesh with density (5r+2)/((r+2)(2r+1)) for even r and (5r+1)/((r+1)(2r+1)) for odd r. The optimal density of a (1,?2)-identifying code in the infinite hexagonal mesh is shown to be 2/3 and the optimal densities of (1,?3)- and (2,?3)-identifying codes are shown to be 1.     

Greedy algorithm for scheduling batch plants with sequence‐dependent changeovers

This article presents a new algorithm for scheduling multistage batch plants with a large number of orders and sequence‐dependent changeovers. Such problems are either intractable when solved with full‐space approaches or poor solutions result. We use decomposition on the entire set of orders and derive the complete schedule in several iterations, by inserting a couple of orders at a time. The key idea is to allow for partial rescheduling without altering the main decisions in terms of unit assignments and sequencing (linked to the binary variables) so that the combinatorial complexity is kept at a manageable level. The algorithm has been implemented for three alternative continuous‐time mixed integer linear programing models and tested through the solution of 10 example problems for different decomposition settings. The results show that an industrial‐size scheduling problem with 50 orders, 17 units distributed over six stages can effectively be solved in roughly 6 min of computational time. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Long Binary Narrow-Sense BCH Codes Are Normal

Let C be the binary narrow-sense BCH code of length where m is the order of 2 modulo n. Using characters of finite fields and a theorem of Weil, and results of Vladut-Skorobogatov and Lang-Weil we prove that the code C is normal in the non-primitive case if and in the primitive case if where the constant depends only on t. Received January 4, 1994     

The integrative role of the project management office in the front end of innovation

This research addresses management control in the front end of innovation projects. We conceptualize and analyze PMOs more broadly than just as a specialized project-focused organizational unit. Building on theories of management control, organization design, and innovation front end literature, we assess the role of PMO as an integrative arrangement. The empirical material is derived from four companies. The results show a variety of management control mechanisms that can be considered as integrative organizational arrangements. Such organizational arrangements can be considered as an alternative to a non-existent PMO, or to complement a (non-existent) PMO's tasks. The paper also contrasts prior literature by emphasizing the desirability of a highly organic or embedded matrix structure in the organization. Finally, we propose that the development path of the management approach proceeds by first emphasizing diagnostic and boundary systems (with mechanistic management approaches) followed by intensive use of interactive and belief systems (with value-based management approaches). The major contribution of this paper is in the organizational and managerial mechanisms of a firm that is managing multiple innovation projects. This research also expands upon the existing PMO research to include a broader management control approach for managing projects in companies.