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EgeUn###, Ceiba pentandra (L.) Gaertn (kapok) fiber, a natural and renewable material, has received increasing attention in recent years for its intrinsic properties. In this study, pretreatment of kapok fiber was performed in a green way by using atmospheric plasma, together with pectinase and lipase enzymes and no hazardous chemicals was used. A response surface methodology (Box-Behnken experimental design) has been used to design and optimize an environmentally friendly and sustainable scouring process for kapok fibers. Predicted values provided from regression model and the actual experimental values exhibited close relationship. The effects of the treatments on the hydrophility, whiteness index and color yield of the kapok fibers have been discussed. The structure of the fibers was investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analyses. Results showed that atmospheric plasma + pectinase and atmospheric plasma + lipase treatments are ecofriendly alternatives for kapok fiber treatments.

Insect repellent textiles are currently being investigated as a complementary tool to control disease vectors, such as mosquitoes. The application of microencapsulated biopesticides to textiles is a promising low-toxicity alternative to other control methods, as microcapsules may prolong the release of the repellent agent. In this work, microcapsules containing two biopesticides, namely citronella essential oil and citriodiol® were prepared and applied to cotton textiles using a variety of techniques. The aim of this work was to evaluate these functional textiles to select the most efficient, durable systems. Citriodiol-treated cotton presented a prolonged durability, and 100% repellency could be achieved for more than 30 days after padding onto cotton fabrics. It has to be pointed out that all these repellent textiles have been obtained by scalable, low-cost methods which would require no additional investment for textile finishing industries., Facultad de Ciencias Naturales y Museo, Centro de Estudios Parasitológicos y de Vectores

WOS: 000400069000006, Silver compounds have extensive use among the antimicrobial agents in textiles. Silver particles are released into the water during washing processes in particular and they are released from the textile in time due to use. In this work, silver ion release from cotton and polyester antimicrobial fabrics which are the most widely used textiles have been studied. Two well-known silver-based commercial agents and silver-doped calcium phosphate powder-based antibacterial finishing agent which was developed in our previous work were applied to the fabric samples. The release of silver from the fabric samples during washing and incubation was determined by ICP-OES. The effects of fabric composition, time and laundering process on the silver release were studied. It was found that significant amount of silver was released from textile fabrics during washing due to the mechanical forces exerted on the fabrics. The total released silver varied from 73.43 to 92.27% for cotton fabrics and 76.49 to 89.70% for PES fabrics after 20 washing cycles. Results also showed that calcium phosphate can reduce the amount of silver release significantly. It was also found that even a smaller quantity of nanosilver particles was sufficient for strong antibacterial activity., Anadolu University Scientific Research Projects Commission [1108F128], This study was supported by Anadolu University Scientific Research Projects Commission [grant number 1108F128].

For manufacturing companies, quality management is a key feature for increasing the competitiveness, productivity, profitability, and sustainability of their systems. Quality improvement (QI) methods aim to achieve high-quality parts without reducing performance. The Industry 4.0 framework brought technological developments that cannot be used by traditional QI methods, such as Six Sigma, Lean, Lean Six, the Theory of Constraints, and Total Quality Management, which are widely used in manufacturing companies. The need for higher manufacturing sustainability and market requirements has led to the search for alternative QI methods with superior performance to traditional QI methods such as Zero-Defect Manufacturing (ZDM). The current paper is a position paper with a goal to present the ZDM approach and providing a clear definition about ZDM to align everyone in one common understanding of ZDM. Many researchers and manufactures are skeptical about ZDM, therefore, numerous argumentative questions have been created and answered, to convince them why they should migrate from traditional QI methods to ZDM. The migration to ZDM has already started, to support this statement numerous facts from the literature have been presented. Finally, several directions were identified, demonstrating that there is still plenty of room for research in several domains.

In this paper, we study the influence of seasonal demands and forecasts on the performance of an Automatic Pipeline, Variable Inventory, Order-Based, Production Control System (APVIOBPCS) using linear control theory. In particular, we consider a system that uses a seasonal forecast based on a no-trend, additive-seasonality exponential-smoothing model, and compare its performance to an equivalent system using simple exponential smoothing. We find that the system with seasonal forecasting significantly outperforms the system with simple exponential smoothing under certain demand assumptions. With optimal parameter settings, the forecast error of the seasonal model can be up to 40% lower. However, we also find that the forecast superiority does not necessarily translate to the performance of the system measured through the bullwhip metrics. In addition, the seasonal forecasting model is very sensitive to the demand frequency and smoothing parameters, while the simple exponential smoothing model is very robust. This implies that the real life benefits of implementing a seasonal forecasting model are not obvious and depend on the particular situation; under a large number of settings (e.g. low seasonality, high-smoothing), the good performance of simple exponential smoothing certainly justifies its popularity in the industry and research worlds alike.

Lean Thinking has successfully challenged mass production practices, by providing 'leaner' processes and supply chains, i.e. with less waste. Industry 4.0 has become an important strategic approach in the technological change of manufacturing and others. It aims to connect the physical and virtual worlds in industrial production. With such automation associated with Industry 4.0, questions arise about the synergy between this approach and the role of Lean in this ongoing industrial revolution. Therefore, a systematic literature review was carried out in order to identify the role of Lean in this scenario. The review was conducted from 2011 to 2019 timeframe and resulted in a total of 33 papers. This review demonstrated this as an emerging research area with most of the studies published in recent years (2017-2019). A deep analysis was undertaken to understand the Lean effect as a trigger for Industry 4.0. Main findings from a 15 out of the 33 papers revealed elements and facts found in sentences of such papers that act as this trigger. Additionally, a words count indicated that management, processes and people were the most cited words by the 15 papers, reinforcing the role of these key players in the companies' transformation., This work was supported by the Fundaçãoo para a Ciênncia e a Tecnologia.

This paper is intended to provide a scoping review on interfaces in service modularity. There is little detailed understanding of this concept despite its attributed importance. We identified 12 papers, showing that interfaces in service modularity are an area still open to research, especially with regard to interfaces that cross organisational boundaries. We found common themes in the available literature: the nature of interfaces, service fragmentation and predefined interfaces. Further research is needed on interfaces in service modularity, especially for complex services with components that stem from multiple, autonomous organisations. More specifically, there is a need for more studies that explore in detail how interfaces manifest themselves, and how they can be addressed to improve complex service provision. In addition, we argue why healthcare could be an interesting domain in which to conduct those studies. Our paper’s contribution comprises a detailed description of interfaces in service modularity, the dissemination of summarised research findings and suggestions for potential future research.

The construction type of reinforcement material is a critical factor playing an essential role in the mechanical performance of composite materials. Recently, much attention has been attracted to discovering the mechanical behaviour of glass woven fabric, such as plain and different variations of twill and satin reinforced composites. In this paper, it is aimed to test the effect of a combination of unique characteristics of woven and knitted fabrics in the same matrix on the mechanical behaviour of composites. In this direction, carbon tows are fabricated into plain woven, 2/2 twill woven and interlock knitted fabrics. The effect of reinforcement construction on bending and tensile properties like strength, modulus and strain of epoxy composites manufactured in three variations as woven, knitted and woven/knitted reinforced was investigated by conducting 3-point bending and tensile tests. Experimental results indicated that hybrid composites displayed lower bending strength than woven fabric composites. However, a combination of 2/2 twill woven and knitted fabric in hybrid composites, including five fabric layers, had a higher bending modulus than 2/2 twill woven composites, including seven fabric layers. Also, it was observed that the mechanical performance of hybrid composites under tensile load was poor compared to the woven fabric composites.

Complex product and production systems often result in high variability in the production flow, prohibiting the sustainable implementation of lean practices. In this paper the authors introduce a PDCA cycle to analyse and reduce variability in value streams. The value stream is divided into zones, which are then qualified as stable or unstable. Lean practices can be applied in stable zones, unstable zones remain expert-driven. Measures are introduced to reduce variability in unstable zones with the ultimate target, to turn them into stable zones, extending sustainable lean activities in the value stream, step by step. An IT system is developed to acquire, process and visualise the vast amount of data to provide structured information for experts and management for the reduction of variability in production.

This paper considers a low-level unit-load warehouse employing single-deep storage lanes and a single-command manual storage and retrieval policy. Analytical travel distance models are developed for class-based and full turnover storage policies under across-aisle, within-aisle and a newly proposed hybrid product placement schemes. Our computational studies show that the analytical models developed in this paper are very accurate as compared to simulation results and a comparative study with a real-world warehouse case. Hybrid storage policies proposed in this paper outperform all other traditional storage policies. The paper also presents insights and simple design rules to warehouse practitioners.

Advances in production planning and control in recent decades have focused on increasing the sophistication of the planning function. For good reasons, these advances have led to the centralisation of the planning function in production. However, the sophistication of the planning function should be in balance with monitoring and control of the plan. Monitoring and control are by their nature decentralised, beginning on the shop floor, and, therefore, the desire for greater sophistication in monitoring and control leads to renewed interest in decentralised and localised approaches. This paper demonstrates the possibility of using intelligent products for decentralised monitoring and control. Intelligent products are aware of their local context and can negotiate with local manufacturing resources. As such, local solutions to problems can be proposed directly when problems occur. With the advancement of the 'Internet of Things', such a scenario is likely to become feasible in the near future. The paper demonstrates the viability of such an approach through a simulation study, in which robustness is included as an additional measure of performance. The results of the simulations are encouraging.

This paper addresses the process of event handling and rescheduling in manufacturing practice. Firms are confronted with many diverse events, such as new or changed orders, machine breakdowns, and material shortages. These events influence the feasibility and optimality of schedules, and thus induce rescheduling. In many manufacturing firms, schedules are created by several human planners. Coordination between them is needed to respond to events adequately. In this paper, the practice of coordination during event handling is analysed by an extensive case study. The study shows that human planners spend much time in communicating events and in negotiating rescheduling solutions. Because many events demand a quick response, the possibilities for coordination are restricted by time constraints. The paper proposes a procedure to structure the event handling process. This procedure helps a scheduler to select an appropriate response to an event by evaluating its influence on schedule feasibility and the time available for coordination and rescheduling. The use of the procedure in the case company has led to improved rescheduling performance through a reduction of scheduler interactions and increasing coordination efficiency. The procedure contributes to traditional planning frameworks and paradigms, and supports the conscious selection and use of rescheduling methods in manufacturing practice.

This paper presents an exploratory study on the knowledge and importance of integrating Lean Education in curricula from the Academy perspective. The study was based on the analysis of participants' outcomes of workshops settled in international conferences. These workshops were used to promote Lean Education as a fundamental content and competency to be taught to the new professionals, independently of their future activity. Having in their DNA Lean content and competency, professionals will be thinkers adopting whole system-thinking, a sustainable conscious and ethical behaviour prepared to face Fourth industrial revolution demands. The authors believe that Lean Education provides such competencies to the new professionals and have been settling and operationalized such workshops in different contexts, involving more than 100 participants (mainly, academics) with teaching responsibilities in training the future workforce. Workshops outcomes were obtained from participants' active discussions and through a satisfaction assessment questionnaire filled by all participants at the end of the workshop. Results show that Lean Education is valuable by academics (more than 50% of the participants gave a high score to the practicality, value, and timeliness of the workshop contents). Nevertheless, a small percentage (12%) knows what Lean Education is or teaches Lean in the classes (10%)., This work has been supported by Fundacao para a Ciencia e Tecnologia (FCT) within the Project Scope: UID/CEC/00319/2019.

The effect of time bucket length on the choice of a lot-splitting approach is studied. Due to the continuing pressure to reduce throughput times and increase efficiency, managers apply various measures, such as lot splitting and cycle time reduction programmes, that change the length of the time bucket in their planning systems. It is shown that the choice for a suitable lot-splitting approach depends on the time bucket length used, so these measures cannot be treated independently as costs may increase rapidly without substantial effect on throughput times. Moreover, the current belief in the lot-splitting literature that the improvements of a variable lot-splitting approach are only marginal compared with an equal sub-batch approach is challenged. Some papers estimate the possible flow time improvement to be less than 5%. It is shown that such statements are not valid as the improvement depends strongly on the type of equal sub-batch strategy applied and the length of the time bucket. Moreover, flow time improvements are accompanied by extra transfer costs, so a cost perspective that includes both effects is more appropriate. The paper shows that equal sub-batching is only effective if information on the time bucket length and on product characteristics is included. At time bucket lengths between one and three days, costs are very sensitive for the type of sub-batching strategy applied. Simulation experiments show that variable sub-batching leads to average cost improvements from 3 to 11%, depending on the time bucket length and the equal sub-batch strategy applied. Lower costs are due to throughput time reductions and transfer cost savings.

Warehouse operations are vital for the success of a supply chain. This paper explores fit among warehouse management structure and the context in which the warehouse operates as an important driver of warehouse performance. Warehouse management structure has been operationalised as the extensiveness by which warehouse operations are planned and controlled, and the complexity of the decision rules used for optimisation of the operations. Warehouse performance is measured using data envelopment analysis (DEA). Hypotheses are developed and tested in a survey study among 111 distribution warehouses in the Netherlands and Belgium. Our results show that indeed warehouse management structure should be adapted to context. In order to obtain high warehouse performance more complex warehouse tasks require more and more complex decision rules, and warehouses with more unpredictable demand require fewer tactical plans. These results can help warehouse managers to structure their warehouse management contingent on the context in which the warehouse operates.

E-commerce companies often use manual order-picking systems in their warehouses since these systems can provide the required flexibility and scalability. Manual systems have been widely studied, but the operating policies may require significant changes for e-commerce settings. First, to maintain consumers' loyalty, it is important to maintain delivery reliability even on the busiest days. When the number of order pickers in an area increases, however, more delays due to interactions may occur. For example, travel speed may need to be lowered when order pickers pass each other in narrow aisles. Second, many products sold through e-commerce are returned by consumers. Before these returned products can be sold again, they must be reintegrated in the stock. This paper presents hybrid genetic algorithms to determine routes for simultaneous pickup of products in response to consumers' orders and delivery of returned products to storage locations. Furthermore, interactions between the order pickers are considered in the routing decisions. The developed algorithms use specific warehouse problem characteristics. We identify the mix of pickups and deliveries to realise the highest savings in practice. It is shown that order-picker interactions can be a significant cause for delay and should be accounted for in the routing.

0000-0001-5333-5750, WOS: 000477771800005, C120 steel sections are the most widely used post shapes in European guardrail designs. The design length of these posts is determined based on guardrail containment level and engineering judgment. The soil properties where these posts are embedded are usually not considered in design. It is a well-known fact that the crash test performance of soil embedded posts depends mostly on post-soil interaction and post embedment depth (PED). In this study, a series of field impact tests were performed on soil embedded C120 posts to determine optimum PED for three different soil conditions. Seven different PED varied from 650 to 900mm was used for each soil type. Based on these findings a full-scale crash test is performed on a guardrail to verify optimum PED for hard soil conditions. With the use of optimum length guardrail posts considerable amount of installation time, labor and material savings are expected., TUBITAK (Scientific and Technological Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [213M516], The work presented in this paper was carried out with funding from TUBITAK (Scientific and Technological Research Council of Turkey), Grant number 213M516. Their support to this study is gratefully acknowledged.

In this paper, we investigate the use of a continuous algorithm for the no-idle permutation flowshop scheduling (NIPFS) problem with tardiness criterion. For this purpose, a differential evolution algorithm with variable parameter search (vpsDE) is developed to be compared to a well-known random key genetic algorithm (RKGA) from the literature. The motivation is due to the fact that a continuous DE can be very competitive for the problems where RKGAs are well suited. As an application area, we choose the NIPFS problem with the total tardiness criterion in which there is no literature on it to the best of our knowledge. The NIPFS problem is a variant of the well-known permutation flowshop (PFSP) scheduling problem where idle time is not allowed on machines. In other words, the start time of processing the first job on a given machine must be delayed in order to satisfy the no-idle constraint. The paper presents the following contributions. First of all, a continuous optimisation algorithm is used to solve ...

The workload control literature highlights the importance of balancing the shop floor workload, but also acknowledges that this can conflict with processing the most urgent orders – hence, there is a trade-off. In practice, shops contain many complexities, e.g. simultaneous batching and sequence-dependent set-up times that may conflict with processing the most urgent orders and require other solutions than workload balancing to avoid capacity losses. This adds to the trade-off dilemma, which traditionally only considers timing and balancing. This paper develops a framework that determines whether to address a complexity through order release or dispatching. It comprises two dimensions: (i) the typical position of a complexity in the routing of an order and (ii) the criticality of the complexity. A case study is presented, which demonstrates the framework’s utility and illustrates the development of specific solutions designed to handle the complexities. Most complexities present in the case require handling at the order release stage. The challenges of handling multiple complexities at this decision level are evaluated. Finally, the implications for managers and future research are outlined.

International audience; Self-storage warehousing is a rapidly growing industry where consumers or companies can rent storage space for personal or company use, over a certain horizon. This paper addresses the question of how to design the facilities so that revenue can be maximized over a nite horizon, considering multiple demand requirements with respect to size, pricing, location within the facility, climate control, security, or outside access, among others. Using a customer choice model to specify the probability of purchase for each fare product as a function of the set of fare products offered, we propose methods to design self-storage warehouses while allowing different customer choice behaviors. We model the problem as a mixed-integer program and solve it using column generation and branch-and-price algorithms. In addition, we study the impact of re-layout and methods to modify facility layout, since self-storage facilities are relatively fexible in layout and individual storage compartments can be adapted to changes in demand. We validate our model using the data of four self-storage warehouses, and show our method can improve the expected revenue by nearly 11% on average for these cases.

The consignment stock (CS) is an innovative approach to manage inventories in which the vendor removes his inventory and maintains a stock of materials at the buyer's plant. The aim of this paper is to promote a successful application and comprehension of the CS policy both in literature and practice. In this paper, we deal with a multi-echelon inventory system in which one vendor supplies an item to multiple buyers. The study develops a single-vendor and multi-buyer consignment stock inventory model in which many clients can establish a CS policy with the same vendor. The aim of the paper is to evaluate the real economical and logistic benefits from the point of view of both the partners and the whole supply chain, following the adoption of a CS policy. We determine the maximum and minimum inventory stock levels to store in the buyers’ plant warehouse and the optimal quantity delivered from the vendor to each buyer in order to minimise total supply chain costs. Space constraints in clients’ plant warehou...

In the past three decades, the magnitude of business dynamics has increased rapidly due to increased complexity, uncertainty and risk of international projects. This fact made it increasingly tough to ‘go alone’ into the international projects. As a consequence, companies with diverse strengths and weaknesses cooperatively bid for joint ventures (JV) formation. Joint venture is also a well-established aspect of the crude oil industry, specifically in the upstream segment. Making decision on the optimal form of JVs is still a challenging problem. In addition, the success of a JV is intertwined with the accuracy of the partner selection phase. Therefore, this paper formulates a multi-criteria mathematical model to select the best partners and form an optimal JV for undertaking oilfield projects. The lexicographic goal programming technique is employed to minimise undesirable deviations from diverse goals such as resources needs (technological and expertise), budgetary requirements, time, etc. The model is validated with a real-life-based example and provides insightful views on alternative formats of cooperation.

Form postponement (FP) is an operations design approach that has been proposed in the literature as a solution for companies to handle increasing product variety and demand uncertainty. FP is possible in food, but the few authors that studied FP in food stress that food characteristics limit the benefits of applying FP. In this paper, we study how characteristics of the food processing industry affect the operational performance of implementing FP based on a case in a dairy company and a simulation model. We found that substantial operational performance improvements could be achieved when implementing FP diminishes the negative effects of some typical food processing industry characteristics. Large gains are possible in production settings with restricted batch sizes and cyclical plans that heavily influence the timing of production. However, a premise to maximise the FP benefits is that the other planning activities should match the new capabilities. Benefits are lower if the company cannot or does not ...

The International Journal of Production Research has successfully navigated through its first 50 years while remaining truthful to its initial editorial goals of publishing interdisciplinary work that is both relevant and rigorous. Will the journal be equally successful in the decades to come? Surely, the world has gone through huge changes and we now are part of global interconnected networks that make us vulnerable to new or at least unfamiliar phenomena. We have added expressions like black swans to our lexicon. The world has experienced both natural tsunami and business tsunami, which we term grey swans. This article describes characteristics of these grey swan business tsunami and argues that our current dominant toolkit of parsimonious analytical models may fall short of passing the test of interdisciplinary work that is both relevant and rigorous. IJPR needs to reflect upon what type of papers to encourage to keep on its original course and provides answers on how to deal with today’s grey swans.

The response time of a storage system is mainly influenced by its shape (configuration), the storage assignment and retrieval policies, and the location of the input/output (I/O) points. In this paper, we show that the optimal shape of a storage system, which minimises the response time for single command cycles, is independent of the used storage policy and the location of the I/O point. This means decisions on the shape of the storage system and storage policy can be decoupled. This simplifies system design since at the design stage little information on customer demand is available. The storage system can then be designed for optimality assuming a random storage policy. Such a system optimally accommodates other time-saving storage policies such as class-based or full-turnover-based storage without requiring configuration correction. © 2013 Taylor & Francis.

Workload control (WLC) is a well established production planning and control concept for make-to-order companies. The main insights into WLC are being gained from stationary simulation studies. Knowledge on its functioning in practice is limited, especially in a dynamic setting. The aim of this paper is to identify and classify the key issues when WLC is being used to control logistical performance in a dynamic setting. For this purpose an empirical research project in a company is carried out, in which both quantitative scanning data and qualitative workshop data are obtained and analysed over one year. Throughput diagrams and order progress diagrams support the analysis of the quantitative data obtained. Various types of dynamics could be discerned, but all implying similar requirements in terms of adaptations to the control concept. Whereas research in stationary settings addresses parameter choices, this study shows that it is issues on timing and magnitude of control adjustments that need to be addressed if WLC is to be used effectively in a dynamic setting. The empirical study shows that if the dynamics are not adequately taken into account, buffers may starve while throughput times become uncontrolled over time, despite the use of WLC.

Unit-based pull systems control the throughput time of orders in a production system by limiting the number of orders on the shop floor. In production systems where orders can follow different routings on the shop floor, route-specific pull systems that control the progress of orders on the shop floor by placing limits on the number of orders in (parts of) a routing, have shown to be effective in controlling throughput times. This is because route-specific pull systems are able to create a balanced distribution of the amount of work on the shop floor, which leads to shorter and more reliable throughput times. The placement of limits on work-inprogress in a route-specific pull system determines to a large extent the workload balancing capability of such a system. This paper shows how the placement of work-in-progress limits affects the workload balancing capability and thereby the throughput time performance of a route-specific unit-based pull system, namely POLCA.

In this paper, we investigate how buyers' and suppliers' distinct perceptions of technology uncertainty affect the relationship between communication frequency and supplier performance. Information processing theory suggests that a fit is desirable between perceived environmental uncertainty and the communication processes between organisations. However, if partners in a buyer-supplier relationship do not concur on the high level of technology uncertainty, it is highly questionable whether increased communication will be effective in increasing supplier performance. Using dyadic data from 86 buyer-supplier relationships, involving 388 respondents, we found that communication frequency was positively related to supplier performance only when both suppliers and buyers perceived high levels of technology uncertainty. When buyers perceived greater technology uncertainty than their suppliers, communication frequency was negatively related to supplier performance. The findings in this study show that it is important to take the distinct perceptions of buyers and suppliers of technology uncertainty into account when assessing the effects of communication frequency. It appears that increased communication is only effective when both parties acknowledge the need to communicate, and can be unfavourable when only one party sees the benefits of it.

Cross-training is becoming increasingly important to firms in order to cope with the more stringent performance requirements they are faced with in today's market. However, many firms put considerable effort into cross-training their workers only to find out that their workers favour the familiar tasks and hardly use and maintain the newly acquired skills. In this paper we explore the hypothesis that reducing the amount of work in process in a constant work in process (CONWIP) controlled job shop with worker preferences forces workers to make a more balanced use of the skills they possess. We test this hypothesis by means of a simulation study with the level of cross-training as moderating variable. Based on this study, it can be concluded that the control and limitation of the amount of work in process breaks the pattern of workers remaining at their preferred machines and constrains the workers to use and maintain their other skills more.

POLCA is a material control system designed for make-to-order or engineer-to-order companies. These firms have to cope with a high variety of customised products, and strong pressure to provide short throughput times. POLCA constrains the amount of work in progress on the shop floor in order to achieve a short average shop floor throughput time. Earlier work has shown that the POLCA system has the capability to reduce both the average shop floor throughput time and the average total throughput time, but it is only effective if the POLCA system has been appropriately designed. The design of the POLCA system is therefore being investigated and discussed in this paper. We give an extensive literature review and give attention to the authorisation mechanisms of POLCA, the design of control loops, the route-specific capacity signals (POLCA cards), and specific facilities needed to use the POLCA system in practice. Finally, we report on the design of a POLCA system in practice, the first complete implementation of POLCA in The Netherlands, and present the quick scan that was used in the design of the POLCA system for this SME.

Compact, multi-deep three-dimensional (3D), Automated Storage and Retrieval Systems (AS/RS) are becoming more common, due to new technologies, lower investment costs, time efficiency and compact size. Decision-making research on these systems is still in its infancy. This paper studies a particular compact system with rotating conveyors for the depth movement and a Storage/Retrieval (S/R) machine for the horizontal and vertical movement of unit loads. The optimal storage zone boundaries are determined for this system with two product classes: high- and low-turnover, by minimizing the expected S/R machine travel time. We formulate a mixed-integer non-linear programming model to determine the zone boundaries. A decomposition algorithm and a one-dimensional search scheme are developed to solve the model. The algorithm is complex, but the results are appealing since most of them are in closed-form and easy to apply to optimally layout the 3D AS/RS rack. The results show that the S/R machine travel time is significantly influenced by the zone dimensions, zone sizes and ABC curve skewness (presenting turnover patterns of different products). The presented results are compared with those under random storage and it is shown that significant reductions of the machine travel time are obtainable by using class-based storage.

In this paper, we consider a newly designed compact three-dimensional automated storage and retrieval system (AS/RS). The system consists of an automated crane taking care of the pallets' movements in the horizontal and vertical direction. A gravity or powered conveying mechanism takes care of the pallets' depth movement in the rack. Our research objective is to analyze the system performance and optimally dimension the system. For single-command cycles, the crane's expected retrieval travel time is the same for gravity and powered conveyors; we give a closed-form expression. From the expected travel time, we calculate the optimal ratio between three dimensions that minimizes the travel time for a random storage strategy. In addition, we derive an approximate travel time expression for dual command cycles for the system with powered and gravity conveyors, respectively, and use it to optimize the system dimensions. Finally, we illustrate the findings of the study by a practical example.

Today's manufacturing companies have strived to develop a large variety of customer-specified products in an effort to survive and stay competitive. Process platforms have been well recognized as a means for companies to obtain a stable production and thus the economy of scale. A process platform assists companies in configuring similar production processes for producing families of customized products at low costs through managing product and process variety coherently. Within a process platform, all data related to the product and process families are unified as a common generic structure. To shed light on the various constituent elements and complex relationships inherent in a process platform, this paper emphasizes the structural representation of a process platform. A formalism of process platform representation is developed based on the Unified Modelling Language. It consists of a generic product structure, a generic process structure and an integrated generic routing structure. Also reported is a c...

Küçükkoç, İbrahim (Balikesir Author), Assembly lines are usually constructed as the last stage of the entire production system and efficiency of an assembly line is one of the most important factors which affect the performance of a complex production system. The main purpose of this paper is to mathematically formulate and to provide an insight for modelling the parallel two-sided assembly line balancing problem, where two or more two-sided assembly lines are constructed in parallel to each other. We also propose a new genetic algorithm (GA)-based approach in alternatively to the existing only solution approach in the literature, which is a tabu search algorithm. To the best of our knowledge, this is the first formal presentation of the problem as well as the proposed algorithm is the first attempt to solve the problem with a GA-based approach in the literature. The proposed approach is illustrated with an example to explain the procedures of the algorithm. Test problems are solved and promising results are obtained. Statistical tests are designed to analyse the advantage of line parallelisation in two-sided assembly lines through obtained test results. The response of the overall system to the changes in the cycle times of the parallel lines is also analysed through test problems for the first time in the literature., Balikesir University Turkish Council of Higher Education

Recent dismal economic conditions and a ruthlessly competitive environment have forced many companies to restructure, or reorganize their priorities. For such companies, the concentration of various resources upon their particular corporate strong points has become a central strategy. Consequently, there has been a rapid increase in the importance of (1) selecting profitable projects from a wealth of possible alternatives and (2) optimizing the allocation of current resources among the selected projects. This paper proposes an optimization system for project selection that not only yields the most beneficial project set, but also the optimum allocation of human resources for the selected projects. The optimization system consists of two algorithms, namely (1) a project selection algorithm for choosing the set of projects that maximizes the total estimated profit, and (2) a human resource allocation algorithm for optimally placing human resources among the selected projects, having considered the satisfact...

Many highly accurate computer tools have been developed for production line design, such as simulation of assembly processes and virtual reality techniques, but these tools require much input information and are generally utilized only in detailed design stages. This paper proposes a rapid analysis method for manual assembly line design, which can be utilized in the conceptual design stage. This method is based on a layout tool with which design engineers can construct assembly line models using 2- and 3-D views, and then employ design evaluation techniques for numerous important criteria such as volume flexibility, and visibility, using the layout data. Spatial evaluation and quantitative efficiency analyses can be simultaneously performed, which enhance collaborative decision-making in the conceptual design stage. This method is applied to an assembly line design for an automobile air-conditioner part as a case study, illustrating the efficiency of utilization in the conceptual design stage that the pro...

The workload control concept is known as a robust shop floor control concept. It is especially suited for the dynamic environment of small- and medium-sized enterprises (SMEs) within the make-to-order sector. Before orders are released to the shop floor, they are collected in an ‘order pool’. To make the release decision, information regarding the actual situation on the shop floor is required. Within SMEs, this information is often incomplete, incorrect or delayed. However, the workload control approaches discussed in the literature assume precise feedback information. The paper discusses the opportunities for information feedback from the shop floor for centralized order release within SMEs and analyses the information requirements of workload control approaches. These approaches are adapted based on more realistic assumptions regarding information supply within SMEs. The different approaches are compared and assessed by a simulation study. Results show that additional investments in more accurate information supply lead to decreasing marginal improvements in overall shop performance. Additionally, they indicate that the choice of the right workload control approach might have important effects on performance.

Almost all the research on the economic lot scheduling problem (ELSP) considering limited shelf life of products has assumed a common cycle approach and an unrealistic assumption of possibility of deliberately reducing the production rate. In many cases, like in food processing industry where limited shelf life for products is common, changing the production rates is not allowed at all because it may result in products with poor quality. In this paper, we allow products to be produced more than once in a cycle and do not allow reducing production rates. We present a modification to the Haessler's basic period procedure to account for the shelf life. Proposed 'branch-and-bound like' procedure exploits these extra constraints to efficiently achieve a feasible solution. Numerical examples are presented to show that our approach outperforms common cycle approach with shelf life considerations.

Labour flexibility is an important issue in the design and development of teams. By means of an analytical study this paper investigates the impact of cross-training on team performance. Four cross-training policies are distinguished and compared according to their effects on important performance measures, such as the load of the bottleneck worker and the number of newly used qualifications seen in various situations. These measures indicate a team's effectiveness and efficiency. Furthermore, they are related to psychological, social and organizational aspects of team functioning. A task assignment heuristic serves as a tool for comparing the cross-training policies. This is applied in an experimental study in which the team situation varies with respect to the cross-training policy, the level of absenteeism, and the variation in the mix of orders. It is shown that a worker-oriented cross-training policy, which attempts to spread multi-functionality evenly among employees, performs well. This policy offers the opportunity to shift work among employees to keep the load of the bottleneck worker low. The required coordination effort for allocating workers to tasks is also relatively low. In line with previous research, this study shows a diminishing positive effect of expanding the level of labour flexibility. The coordination effort required to apply additional flexibility appears to increase linearly with the amount of additional cross-training. The diminishing positive effect and the linearly increasing coordination effort suggest that managers should critically consider the level of labour flexibility in worker teams.

Self-assessment of performance using the European Foundation for Quality Management (EFQM) Model for Excellence is widespread amongst European organizations. The paper reports the development of a model, based on the evidential reasoning approach from multiple attribute decision-making (MADM), which it is argued helps to reduce the subjectivity of the scoring of an organization's performance against the criteria of the EFQM Model and brings a degree of science into the self-assessment process. The development of the MADM model is based on the people management criteria of the 1998 version of the EFQM Model and tests have been undertaken using two self-assessment submission documents from a major multi-utility organization.

Genetic algorithms (GAs) are efficient stochastic search techniques for approximating optimal solutions within complex search spaces and used widely to solve NP-hard problems. Genetic algorithm includes a number of parameters whose different levels strictly affect the performance of the algorithm. The general approach to determine the appropriate parameter combination of GA depends on too many trials of different combinations, and the best one of them that produces good results is selected for the programme, which would be used for problem solving. A few researchers studied on the parameter optimisation of GA. In this paper, response surface-dependent parameter optimisation is proposed to determine the optimal parameters of GA. Results are tested for benchmark problems that are most common in mixed-model assembly line balancing problems of type-I.

The main purpose of this paper is to analyze the Turkish handmade carpet industry and to compare it with select Far East countries. In particular the Turkish handmade carpet industry is compared with the handmade carpet industries of Iran India China Afghanistan Pakistan and Nepal. In this context the determinants of handmade carpets in the US market are analyzed empirically. Our results show that the Turkish handmade carpet industry has been experiencing a period of recession in the past decade. Through the relative comparative advantage (RCA) index and the Kreinin-Finger similarity (KFS) index we observed that the RCA index for Turkey indicates that Turkey's RCA has been declining since 1992. However despite this decline the RCA of Turkey was above that of other countries until 1997. But after this the advantage disappeared eventually and was gained by Iran. During this period the other competitors of Turkey showed small increases. Furthermore the empirical results from the gravity model suggests that a 10% real depreciation/appreciation of the US dollar against foreign currency leads to a 0.2% decrease/increase in imports. This finding suggests relatively low exchange rate import pass-through in carpet commodity. The results also support the Linder hypothesis that countries with similar preferences and demand structures will tend to trade more.

The planning problem in the context of a multi-site procurement-production-distribution system (MSPPDS) considered in this paper is motivated from a real life case of a multinational consumer goods company. A robust optimisation model considering model robustness and solution robustness in the objective function is developed for integrated planning in three dimensions. Detailed production, procurement and distribution plans are integrated; countrywide aggregate production plan is integrated with a detailed plan. Similarly the detailed production plans from the previous planning cycle are integrated with current production plans. Constraints on storage space, production capacity and the time lag between procurement, production and distribution activities are captured in the model. Procurement and production plans are treated as 'here-and-now' decisions and the distribution plans are treated as 'wait-and-see' decisions to be implemented based on the realised demand scenario. The model is illustrated using an example problem and also successfully applied to the data of a consumer goods company involving 104,000 variables (with 832 integer variables) and 21,000 constraints.

Significant savings in cost and time can be achieved in rapid prototyping (RP) by manufacturing multiple parts in a single setup to achieve efficient machine volume utilization. This paper reports the design and implementation of a system for the optimal layout planning of 3D parts for a RP process. A genetic algorithm (GA) based search strategy has been used to arrive at a good packing layout for a chosen set of parts and RP process. A two stage approach has been proposed to initially short-list acceptable orientations for each part followed by the search for a layout plan which optimizes in terms of final product quality and build time. The GA uses a hybrid objective function comprising of the weighted measures like part build height, staircase effect, volume and area-of-contact of support structures. In essence it captures the key metrics of efficiency and goodness of packing for RP. The final layout plan is produced in the form of a composite part CAD model which can be directly exported to a RP machine for manufacturing. Design methodology of the system has been presented with some representative case studies.

A monolithic mixed integer linear goal programming (MILGP) model that is developed in this paper produces a time and capacity aggregated production plan, a detailed production plan, a detailed procurement plan and a detailed distribution plan simultaneously to overcome the drawbacks of the hierarchical/sequential planning approaches of not yielding a feasible and/or an optimal plan. The model uses different time-grids and planning horizons for aggregate and detailed planning to reduce the computational burden. The limitations of storage space, raw material availability and production capacity at plants and a requirement of maintaining a minimum level of inventory buffer or forward cover have been modelled. Two heuristics that are proposed to solve the MILGP model gave good quality solutions with an average and the worse case optimality gap of 1.17% and 4.4% respectively when applied to one hundred randomly generated industry size problem instances.

Rapid tooling (RT) processes driven by rapid prototyping (such as stereolithography and selective laser sintering) can reduce mold development lead-time by 50% or more, though there are certain limitations in terms of mold materials, accuracy, and surface finish. This paper presents a systematic approach for manufacturability analysis of molds produced by rapid tooling methods, based on three aspects: mold feature manufacturability, secondary elements compatibility, and cost effectiveness. The geometric features of functional elements of the mold (core, cavity, side core, etc.) are evaluated for manufacturability using fuzzy-analytic hierarchy process (Fuzzy-AHP) methodology. The secondary elements of mold (parting surface, ejectors, cooling lines, etc.) are checked for compatibility with RT mold properties (machinability, wear resistance, and surface evenness). Finally, the cost of RT mold is estimated using a semi-empirical model based on cost drivers and cost modifiers, and compared with that of a conventional mold. The methodology has been demonstrated with an experimental mold. It is useful not only for RT mold process selection, but also for identifying minor modifications to a mold design to improve its manufacturability and economy.

WOS: 000237065500007, Our previous work presented a Petri net-based iterative synthesis policy for deadlock prevention in flexible manufacturing systems (FMS). Given the Petri net model of an FMS prone to deadlock, it aims to synthesize a live controlled Petri net. Its use for FMS control guarantees its deadlock-free operation and high performance in terms of resource utilization and system throughput. At each iteration, a first-met bad marking is singled out from the reachability graph of the Petri net. A well-established invariant-based control method is used to prevent it from being reached. This process is carried out until the net model becomes live. The method proposed is generally applicable, easy to use, effective, and straightforward, although its off-line computation is of exponential complexity. This paper presents two improvements: (a) using the Petri net reduction approach to simplify very large Petri net models so as to alleviate computation effort; and (2) simplifying the invariant-based control method. A number of FMS deadlock problems from the literature are used to illustrate them.

During the last decade, considerable research efforts in the project scheduling literature have concentrated on resource-constrained project scheduling under uncertainty. Most of this research focuses on protecting the project due date against disruptions during execution. Few efforts have been made to protect the starting times of intermediate activities. In this paper, we develop a heuristic algorithm for minimizing a stability cost function (weighted sum of deviations between planned and realized activity starting times). The algorithm basically proposes a clever way to scatter time buffers throughout the baseline schedule. We provide an extensive simulation experiment to investigate the trade-off between quality robustness (measured in terms of project duration) and solution robustness (stability). We address the issue whether to concentrate safety time in so-called project and feeding buffers in order to protect the planned project completion time or to scatter safety time throughout the baseline schedule in order to enhance stability. ispartof: International Journal of Production Research vol:44 issue:2 pages:215-236 status: published

This paper describes a database management system which was the result of a study carried out by Sakarya University and Adapazari Chamber of Commerce and Industry. The aim of the study was to increase the competitiveness of automotive companies in national and global markets by providing financial, economical and technological information regarding product design, supply chain, quality and job satisfaction. The results indicated that it is of vital importance to generate a supply-chain database management system for better selection of suppliers. Due to the huge number of data to be considered in decision-making, computer support seems to be inevitable.

There are several situations in a product recovery environment where products may be disassembled for economical and regulatory reasons. The disassembly line is perhaps the most suitable setting for disassembly of large products (consisting of numerous components) as well as small products received in large quantities. This paper discusses the importance of a disassembly line in product recovery. The objective of the disassembly line is to utilize the available resources as efficiently as possible while meeting the demand for recovered parts. However, there are many complicating matters that need to be considered to create an efficient disassembly line. Our primary goal is to discuss these issues and provide a better understanding of the complications and their effects on the disassembly line. We also demonstrate how some important factors in disassembly can be accommodated to balance a paced disassembly line by modifying the existing concept of assembly line balancing. An example is presented to illustrate the approach.