Mix Flexibility Research Articles

On the role of wake-capture and resonance in spanwise-flexible flapping wings in tandem

Numerical simulations of the flow around spanwise-flexible flapping wings in tandem are reported, focusing on a thrust-generating configuration. Wings of aspect ratio 2 and 4 in forward flight undergo heaving and pitching motion following optimal 2D kinematics. The Reynolds number of the simulations is Re=1000. The effect of flexibility is explored by varying the effective stiffness of the wings, while the effective inertia is kept constant. The aerodynamic performance of the tandem system results from a combination of unsteady aerodynamics mechanisms, fluid–structure resonance, vortex–wing interactions (denoted wake capture in this study) and aerodynamic tailoring. It is found that the aerodynamic performance and structural behavior of forewings are dominated by a fluid–structural resonance. The maximum mean thrust for the forewings is obtained when the driving frequency approaches the first natural frequency of the structure, ωn,f/ω≈1, similarly to what is observed in isolated wings undergoing the same kinematics. On the other hand, hindwings show optimal performance in a broad region near ωn,f/ω≈2, and their aerodynamic performance seems to be dominated by wake–capture and aerodynamic–tailoring effects. The aerodynamic performance of the hindwings is dependent on the flexibility of the forewing, which impacts the intensity of the vortices shed into the wake and the resulting effective angle of attack (i.e., wake capture). The timing between the effective angle of attack and the pitching motion of the hindwing controls the generation of thrust (or drag) of each spanwise section of the hindwing (i.e., aerodynamic tayloring). A proof of concept study on the aerodynamic performance of systems made of wings with different flexibility suggests that they could outperform tandem systems with equally flexible wings. Thus, the optimal mixed–flexibility tandem system is composed by a resonant forewing, which maximizes the thrust generation of the forewing and the intensity of the vortices shed into the wake, and a hindwing whose flexibility must be tuned to maximize wake capture effects.

Is it selfish to be filamentous in biofilms? Individual-based modeling links microbial growth strategies with morphology using the new and modular iDynoMiCS 2.0.

Microbial communities are found in all habitable environments and often occur in assemblages with self-organized spatial structures developing over time. This complexity can only be understood, predicted, and managed by combining experiments with mathematical modeling. Individual-based models are particularly suited if individual heterogeneity, local interactions, and adaptive behavior are of interest. Here we present the completely overhauled software platform, the individual-based Dynamics of Microbial Communities Simulator, iDynoMiCS 2.0, which enables researchers to specify a range of different models without having to program. Key new features and improvements are: (1) Substantially enhanced ease of use (graphical user interface, editor for model specification, unit conversions, data analysis and visualization and more). (2) Increased performance and scalability enabling simulations of up to 10 million agents in 3D biofilms. (3) Kinetics can be specified with any arithmetic function. (4) Agent properties can be assembled from orthogonal modules for pick and mix flexibility. (5) Force-based mechanical interaction framework enabling attractive forces and non-spherical agent morphologies as an alternative to the shoving algorithm. The new iDynoMiCS 2.0 has undergone intensive testing, from unit tests to a suite of increasingly complex numerical tests and the standard Benchmark 3 based on nitrifying biofilms. A second test case was based on the "biofilms promote altruism" study previously implemented in BacSim because competition outcomes are highly sensitive to the developing spatial structures due to positive feedback between cooperative individuals. We extended this case study by adding morphology to find that (i) filamentous bacteria outcompete spherical bacteria regardless of growth strategy and (ii) non-cooperating filaments outcompete cooperating filaments because filaments can escape the stronger competition between themselves. In conclusion, the new substantially improved iDynoMiCS 2.0 joins a growing number of platforms for individual-based modeling of microbial communities with specific advantages and disadvantages that we discuss, giving users a wider choice.

Marine energy harvesting from tidal currents and offshore winds: A 2-DOF system based on flow-induced vibrations

Owing to the effectiveness in addressing the challenges posed by the uncertainty and instantaneous volatility of renewable energy, the complementary exploitation of diverse energy sources has received considerable attention from researchers worldwide. In this context, this study proposes a two-degree-of-freedom marine energy harvesting system to concurrently extract energy from tidal currents and offshore winds. The proposed energy-harvesting scheme consists of two mechanically linked oscillators with alternative bluff bodies, capable of scavenging multiple forms of fluid energy based on flow-induced vibrations. An associated solution method for the fluid-structure interaction was numerically developed to investigate the dynamical response and energy-harnessing performance of the proposed system in detail. The simulation results demonstrated two typical working modes that occur under various inflow conditions. The 1st mode is used for energy harvesting, whereas the 2nd mode is used for vibration alleviation. These modes can be used to promote the converted power and vibration reliability of the proposed system. In contrast to the conventional one-degree-of-freedom energy harvester, the proposed system demonstrated an improved converted power, increasing from 39.13 W to 44.18 W, and a reduced maximum displacement, decreasing from 1.98 m to 1.02 m, exhibiting superior comprehensive performance in terms of converted power, energy conversion efficiency, adaptability to inflow velocity, vibration reliability, and power mix flexibility. Hence, the proposed system offers a novel perspective for the development and implementation of marine energy-harvesting technologies.

A Cost/Benefit and Flexibility Evaluation Framework for Additive Technologies in Strategic Factory Planning

There is a growing demand for more flexibility in manufacturing to counter the volatility and unpredictability of the markets and provide more individualization for customers. However, the design and implementation of flexibility within manufacturing systems are costly and only economically viable if applicable to actual demand fluctuations. To this end, companies are considering additive manufacturing (AM) to make production more flexible. This paper develops a conceptual model for the impact quantification of AM on volume and mix flexibility within production systems in the early stages of the factory-planning process. Together with the model, an application guideline is presented to help planners with the flexibility quantification and the factory design process. Following the development of the model and guideline, a case study is presented to indicate the potential impact additive technologies can have on manufacturing flexibility Within the case study, various scenarios with different production system configurations and production programs are analyzed, and the impact of the additive technologies on volume and mix flexibility is calculated. This work will allow factory planners to determine the potential impacts of AM on manufacturing flexibility in an early planning stage and design their production systems accordingly.

Digitalisation and Modernisation of Hydropower Operating Facilities to Support the Colombian Energy Mix Flexibility

Hydropower plants cover almost 70% of the Colombian electrical demand, were built several decades ago, and present low levels of digitisation compared to other modern power-generation technologies, e.g., wind turbines, solar PV plants, and recently buil hydroelectric plants t. Renovating power plant equipment and investing in modernisation and digitisation can significantly increase the plant flexibility. Those actions will increase a plant’s operational safety and contribute to the solution of environmental and social problems. This work presents the actions followed to extend the lifetime of a 1000 MW hydropower plant operating for more than 40 years. Activities included a residual life status evaluation of generators and component upgrades, among others. The rehabilitation and digitalisation of the generation units allow their integration and remote monitoring so that diagnostic actions can be carried out during a continuous and economically sustainable operation. These activities complement the plan implemented by the company during the last decade to ensure the plant’s operation for another 50 years and its respective integration with nonconventional generation systems at the national level. Besides the generator’s life extension, the main result of rewinding is an increase in the Minimum Breakdown Voltage by almost 140% (from 38.4 kV to 95.6 kV) with respect to the current operation state, ensuring its operation for the following years.

Modeling production disorder: Procedures for digital twins of flexibility-driven manufacturing systems

While the achievement of mix flexibility is a key driver of competitive advantage for a manufacturing organization, it also represents a source of disruption on the shop floor that may compromise managers' ability to diagnose problems, predict behavior, and make decisions adequately. Given this challenge, the digital twin emerges as a potential tool to reestablish managers’ operational visibility. Its architecture allows for a manufacturing system model to be continuously updated and for management support services to be promptly delivered. Although some studies explore the use of the digital twin to solve specific flexibility-related challenges, the literature lacks a normative and systematic approach to guide the application of this technological architecture in a comprehensive set of flexibility scenarios. To address this gap, based on the normative knowledge acquired from the literature and subject-matter experts, we present procedures to design, implement, and use the digital twin within organizations that suffer flexibility-driven disruptions. We demonstrate the application of these procedures through a case in a large automotive parts manufacturer. Results show that the procedures effectively operationalize a digital twin architecture aimed at contributing to the achievement of a flexible production strategy.

Manufacturing flexibility and business environment uncertainty: Establishing supporting practices within manufacturing flexibility

Purpose: There is a growing interest in the role of flexibility in manufacturing companies, especially in its relevance to managing business uncertainties. Several studies have been conducted on manufacturing flexibility, but no study has examined a possible support practice among the practices of manufacturing flexibility. This study explores that literature gap in a Sub-Saharan business environment. Design/methodology/approach: This study adopts a cross-sectional survey approach and criterion sampling method to select and administer its research instrument to respondents of the study. The sample size was 416, and the hypotheses were tested via the structural equation model. Findings: Study revealed that mix flexibility had a direct impact on supply uncertainty; production flexibility had a direct impact on supply uncertainty; and product flexibility had direct and indirect impact supply uncertainties. Volume flexibility is the only flexibility dimension with no impact on supply uncertainty, both directly and indirectly. In addition, product flexibility is the only practice with indirect impact on supply uncertainty. Practical implications: Managers can adopt manufacturing flexibility to combat supply uncertainty. Funding production and product flexibility will enhance capacities in managing supply uncertainties. Managers should establishing product flexibilities prior to other forms of flexibilities. Practitioners considering implementing one dimension can employ production flexibility to limit supply uncertainty, because it has the most impact on supply uncertainty individually. Originality/value: This study contributes to literature by uniquely examining manufacturing flexibility impact on supply uncertainty exclusively. It is also the first empirical investigation into supporting practices among manufacturing flexibility practices in any business environment. Keywords: Manufacturing, Flexibility, Uncertainty, Production.

기업의 노동 유연성이 혁신성과에 미치는 영향

We analyzed using Workplace Panel Survey (WPS) data on the impact of labor flexibility on innovation performance at the firm level. Verifying the impact of labor flexibility on innovation performance, the higher the flexibility of employment adjustment, the higher the level of employee-led innovation is than the industry average, and the higher the flexibility of contingent employment, the higher the probability to stay in copycat-level workplace innovation. In addition, the higher the wage flexibility and functional flexibility of a firm, the higher the probability that the level of employee-led innovation and product/service innovation will exceed the industry average, and the higher the level of workplace innovation. In addition, analysis of the buffering effects of interaction with employment flexibility, the negative impact of the flexibility of contingent employment on workplace innovation has been shown to buffer or convert by wage flexibility and functional flexibility. The findings suggest that, unlike wage flexibility and functional flexibility, employment flexibility does not positively impact innovation performance, so a detailed review of employment flexibility implementation is needed unless very reasonable reasons are involved. And it can be emphasized that mixed flexibility strategies should be used to secure long-term competitiveness from a Paradox perspective.

Labor flexibility integration in workload control in Industry 4.0 era

The paradigm shift toward Industry 4.0 is facilitating human capability, and at the center of the research are the workers—Operator 4.0—and their knowledge. For example, new advances in augmented reality and human–machine interfaces have facilitated the transfer of knowledge, creating an increasing need for labor flexibility. Such flexibility represents a managerial tool for achieving volume and mix flexibility and a strategic means of facing the uncertainty of markets and growing global competition. To cope with these phenomena, which are even more challenging in high-variety, low-volume contexts, production planning and control help companies set reliable due dates and shorten lead times. However, integrating labor flexibility into the most consolidated production planning and control mechanism for a high-variety, low-volume context—workload control—has been quite overlooked, even though the benefits have been largely demonstrated. This paper presents a mathematical model of workload control that integrates labor flexibility into the order review and release phase and simulates the impact on performance. The main results show that worker transfers occur when they are most needed and are minimized compared to when labor flexibility is at a lower level of control—shop-floor level—thus reducing lead time.

Axiomatic design of matrix production systems

Manufacturing companies are operating in a turbulent business ecosystem that demands for product variety, product mix flexibility, volume scalability and high efficiency. Personalized production arises as new production paradigm to replace mass personalization and changeable matrix production systems are well suitable to cope with the challenges of this new production paradigm. In this paper, a method to design the value-add process modules of a matrix production systems is presented. The method is based on Axiomatic Design. The approach works process oriented, pursues a modular layout, and a flexible material flow in the production system. The paper concludes with a validation of the method performed in an industrial use case.

Bio-inspired phylogenetics for designing product platforms and delayed differentiation utilizing hybrid additive/subtractive manufacturing

"Biologicalisation in Manufacturing" is used to integrate biological and bio-inspired processes, principles and resources into manufacturing to handle challenges such as product proliferation. This paper introduces a product variety management methodology utilizing bio-inspired phylogenetics for designing product platforms for the delayed product differentiation using hybrid additive/subtractive manufacturing technologies. The median joining phylogenetic network, an ancestral sequence recognition method used in biology, is applied. This method is used to design product platforms that resemble the common ancestors in nature and determine the process plans for the platform customization that resembles the adaption in nature. A new feature extraction procedure is introduced to extract the additive and subtractive features of a product family. Two case studies, guiding bushings and flanges product families, are used for demonstration. The developed methodology improves the responsiveness and product mix flexibility and decreases the storage costs.

How SERU production system improves manufacturing flexibility and firm performance: an empirical study in China

SERU production system (SERU) demonstrates more manufacturing flexibility in response to volatile market demands. Although many firms have implemented SERU successfully, little research on manufacturing flexibility in SERU exists, especially empirical evidence in the context of Chinese firms. Manufacturing flexibility considers two major dimensions in SERU, namely, product mix flexibility and volume flexibility. We propose a contingency-based framework to explore the source factors of manufacturing flexibility and their impact on firm performance. We examine the moderating effects of both multi-skilled worker turnover and industry type. Using a total of 357 samples from China, we test the hypotheses with structural equation modeling. Our results reveal that both SERU reconfiguration and multi-skilled worker involvement are important sources of product mix flexibility and volume flexibility, and the two kinds of flexibility subsequently improve firm performance. Multi-skilled worker involvement has a stronger impact than SERU reconfiguration on improving manufacturing flexibility. Both multi-skilled worker turnover and industry type are important moderators. We also conduct tests indicating that the mediation effects of manufacturing flexibility are moderated by multi-skilled worker turnover and industry type. Overall, the acquisition of manufacturing flexibility and its impact on performance in SERU are situation dependent.

Companies performance management: the role of operational flexibility

The article summarizes the arguments on minimizing the uncertainty level caused by numerous unforeseen circumstances due to using operational flexibility to increase companies' efficiency (example of small and medium enterprises in the pharmaceutical sector of Iran). The research aims at investigating the relationship between operational flexibility and a company's performance to examine the impact of environmental uncertainty on these relationships. This study was conducted as quantitative. The deductive method using the synergy of systematization of scientific background on the problem and the empirical proof of the formulated hypotheses became a methodological study tool. The article provides evidence of the economic-mathematical model based on data from small and medium-sized pharmaceutical Iranian companies. The study hypotheses are as follows: 1) operational flexibility has a positive effect on the productivity of the pharmaceutical sector of Iran, represented by small and medium-sized companies; 2) uncertainty determines the relationship between the operational flexibility and efficiency of small and medium-sized pharmaceutical companies in Iran. The model constructed by the authors allowed measuring the relationship between variables using regression analysis and moderation analysis (Hayes model). The total number of companies included in the sample is 113. In turn, 228 managers of these pharmaceutical companies took part in the surveys (Iran example). The empirical analysis results showed that the mix flexibility indicator has practically no effect on companies' efficiency, and the volume flexibility and product development flexibility indicators generally have a positive effect on the performance of companies in the pharmaceutical sector. On the other hand, the environmental uncertainty indicator does not help reduce the relationship between the operational flexibility indicator and companies' performance in the pharmaceutical sector of Iran's economy. The study results could be useful for planning small and medium enterprises' activities in the context of improving their performance.

Is Adopting Mass Customization a Path to Environmentally Sustainable Fashion?

Problem definition: In high-product-variety businesses like fashion, mass production (MP) systems create environmental waste in the form of overproduction on a colossal scale. Mass customization (MC) has been proposed -- without solid evidence -- as a solution. In this paper, we analyze whether MC can indeed offer a win-win solution that helps both the bottom line and the environment. We also study the impact of three real policy options: promoting MC, charging a disposal fee for overproduction, and recycling. Academic/practical relevance: There is increasing interest in mass-customizing fashion goods, not only because consumers value customization, but also because MC is perceived to be environmentally friendly. Our paper puts this advocacy for MC to test. We contribute to the literature, which has been largely silent on the issue, by uncovering when MC offers a win-win and relating such market outcomes to policy ideas. Methodology: We develop an analytical model of an MP firm adopting MC (going hybrid). The firm’s profit-maximizing variety, price and inventory decisions then form the basis of our understanding the environmental impact of adopting MC and assessing various policy options. Results: Adopting MC can be a win-win, but it can also increase overproduction and hurt the environment. Our policy analyses reveal two kinds of insights. First kind is about whether a policy expands win-win outcomes -- encouraging sustainable adoption of MC. Among the policy ideas we explore, only promoting MC so as to increase consumers' tolerance for waiting for mass-customized products can do that unambiguously. Second kind of insight is about whether a policy reduces the hybrid firm's environmental impact. Only disposal fee and costly recycling programs can do that unambiguously. Managerial implications: For MC adoption to be a win-win, policy makers must (1) work on convincing consumers to wait for bespoke fashion, (2) target MP firms with low cost of variety (high product mix flexibility) with disposal fees or costly recycling programs, and (3) encourage those with relatively higher cost of variety to develop/acquire technology that would make recycling profitable.

Generation expansion planning with high shares of variable renewable energies

Worldwide, the utilization of Renewable Energies (REs) for electricity generation is growing rapidly driven by the increasing fears of fossil fuels depletion, the price volatility of these fuels and the necessity of reducing the Green House Gas (GHG) emissions to preserve the environment. On the other hand, REs especially the Variable Renewable Energies (VREs) like wind and solar power suffer from intermittency in its output generation. This intermittency can introduce severe technical and economic problems for the power systems with high penetration from these energies. This intermittency should be mitigated not only during the system operation phase but also during power system planning phase. For this purpose, the classical power system planning methodologies and models should be upgraded to account for this intermittency in a way to find the optimum solutions to mitigate it. In this regard, this paper will focus on developing a new Generation Expansion Planning (GEP) model to find the optimum mix of dispatchable generation technologies that can allow the integration of VREs into the power system while mitigating the technical and economic impacts of its intermittency. In addition, a number of new concepts related to generation mix flexibility, VREs capacity credit and role of system operating reserve in integrating VREs will be revisited. Then, the developed GEP model will be applied to a case study handling the future expansion scenarios of VREs in the Egyptian grid. Results obtained show that, increasing the share of VREs in the grid will shift the mix of new generation capacities from the least cost and low flexibility options into more expensive and flexible generation options.

Implications of realizing mix flexibility in assembly systems for product modularity—A case study

To enable the production of high product variety, mix flexibility in assembly systems is of paramount importance for manufacturing companies. Mixed-product assembly lines (MPALs) are growing as the key means of realizing mix flexibility in many manufacturing sectors, as they absorb volume fluctuations and offer high product variety. With the increasing product variety in MPALs, these assembly systems are becoming more complex. However, the practical challenges of these assembly systems, in particular those concerning product design, have not been adequately addressed. By performing a case study of a heavy machinery manufacturing company, this paper investigates the implications of realizing mix flexibility in an assembly system for product modularity. The findings pinpoint the low level of product modularity in assembly as the most important challenge in MPALs. Accordingly, realizing mix flexibility in an MPAL impacts product modularity through establishing a common assembly sequence and defining similar module contents across distinct product families.

Generic Production System Model of Personalized Production

Manufacturing companies are operating in a turbulent business ecosystem that calls for product variety, product mix flexibility, volume scalability and high efficiency. Personalized production arises as new production paradigm to replace mass personalization. The paper proposes a generic model for the design of production systems for the paradigm of personalized production. The model applies the system design methodology Axiomatic Design and uses the notation of Axiomatic Design Theory for Systems combined with the product precedence graph for product structure modeling. The model represents the static system structure, decomposed into its subsystems, and explains the dynamic behavior of the system during operation, depending on the product’s architecture. It is intended as a reference model for production system planning.

The relationship between internal integration and manufacturing flexibility in the Egyptian industry

PurposeThis paper aims to empirically investigate the triadic relationship between internal integration, internal flexibility and external flexibility.Design/methodology/approachThis research hypothesized the mediation effect of internal flexibility on the relationship between internal integration and external flexibility. Survey data were collected and analyzed using simple and mediation regression analysis to test the study hypotheses.FindingsThe research finding reveals that machine, labor and material handling flexibilities; being as internal flexibility dimensions mediate the relationship between internal integration and volume and mix flexibilities; being as external flexibility dimensions. The results provided insufficient evidence on the mediating effect of routing flexibility on the relationship between internal integration and both volume and mix flexibilities.Research limitations/implicationsThis research presents a new perspective for research studies to understand the factors that affect manufacturing flexibility. However, the nature of the surveyed sample and using of a single informant might limit the generalizability of the research findings.Practical implicationsThis study provides useful insights for firms wishing to enhance their competitiveness through improving their flexibility. The companies should be aware of the importance of developing a suitable platform for coordinating inter-departmental activities to enhance its internal competencies, which, in turn, improve its customer-facing capabilities and boosts its competitiveness.Originality/valueThis paper contributes to knowledge by proposing and empirically testing the mediating effect of internal flexibility on the relationship between internal integration and external flexibility.

Impact of generation mix flexibility on the integration of variable renewable energies

Worldwide, renewable energies are witnessing a huge expansion especially for power generation driven by different factors including the increased demand on fossil fuels and the depletion of its resources, the increase in its cost and the need to preserve the environment. Variable Renewable Energies (VRE) especially depending on wind and solar resources are intermittent by nature and this intermittency can have severe impacts on the operation of the power systems. Power systems are thus required to have a sufficient degree of flexibility to deal with this intermittency especially in the generation side. This paper introduces a hybrid Flexibility Enhanced Priority List-Mixed Integer Linear Programming (FEPL-MILP) method to solve the Unit Commitment (UC) problem and study the impact of the generation mix flexibility on the integration of renewable energies. Results show that, increasing the flexibility of the thermal energy mix used for power generation will have positive technical and economic impacts on the integration of renewable energies into the power system.Keywords: Intermittency, Generation Mix, Flexibility, Unit Commitment

Sustainability and performance in operations management research

Abstract Interest in sustainability and its relation to performance has grown significantly among practitioners and operations management (OM) scholars. However, there is still a paucity of research on the antecedents and drivers of sustainability, as well as on the relationship between sustainability and performance. Moreover, the literature offers contradictory results on this relationship. Therefore, the goal of this paper is to provide a research synthesis about the overall state of the art of empirical research on the impact of sustainability management practices on performance, encompassing social and environmental dimensions. To achieve this goal, the authors develop a rigorous systematic review of the extant literature on sustainability relationships with firm performance, emphasizing the under-researched area of causal models of sustainability and operational performance. This research is a first attempt to go beyond the highly dispersed work on the subject, aiming to provide more generalizable evidence about theories, methods and findings. The synthesis embraces 231 papers in total and identifies the main variables on causal models depicting the relationships between sustainability and performance, analyses how the studies on the subject are conducted, and investigates the impact and the mechanisms through which sustainability affects operational performance (OP). Overall, there are positive effects of sustainability on performance, such as lower costs, better delivery and product quality, enhanced volume and mix flexibility, although different mechanisms drive the sustainability-performance links and they differ according to contexts. The study outlines implications for practice and future research.