Why do nonlinearities matter? The repercussions of linear assumptions on the dynamic behaviour of assemble-to-order systems

The hybrid assembly-to-order (ATO) supply chain, combining make-to-stock and make-to-order (MTS-MTO) production, separated by a customer order decoupling point (CODP), is well recognised in many sectors. Based on the well-established Inventory and Order Based Production Control Systems (the IOBPCS family), we develop a hybrid ATO system dynamics model and analytically study the impact of nonlinearities on its dynamic performance. Nonlinearities play an important, sometimes even a dominant, role in influencing the dynamic performance of supply chain systems. However, most IOBPCS based analytical studies assume supply chain systems are completely linear and thereby greatly limit the applicability of published results, making it difficult to fully explain and describe oscillations caused by internal factors. We address this gap by analytically exploring the non-negative order and capacity constraint nonlinearities present in an ATO system. By adopting nonlinear control engineering and simulation approaches, we reveal that, depending on the mean and amplitude of the demand, the non-negative order and capacity constraints in the ATO system may occur and their significant impact on system dynamics performance should be carefully considered. Failing to monitor non-negative order constraints may underestimate the mean level of inventory and overestimate the inventory recovery speed. Sub-assemblers may suffer increased inventory cost (i.e. the consequence of varying inventory levels and recovery speed) if capacity and non-negative order constraints are not considered at their production site. Future research should consider the optimal trade-off design between CODP inventory and capacity and the exploration of delivery lead-time dynamics.     

To RMC or not to RMC? The use of reverse Monte Carlo modelling

The ‘classical’ approach to structural studies of liquids and glasses, developed over the last 40 years, has been through derivation of the partial pair distribution functions and interpretation of these in terms of peak positions, coordination numbers etc. These parameters are then used to produce a simple picture of the average local structure. An alternative approach, strongly developed in the last decade, is full atomistic modelling of the structure, either by direct modelling of experimental data using techniques such as reverse Monte Carlo modelling (RMC) or empirical potential structure refinement (EPSR), or indirectly through simulation techniques such as Monte Carlo (MC) or molecular dynamics (MD), or more recently ab-initio MD. In this comment we raise some questions that should be considered before a decision is made to use any particular method. We then illustrate, with a particular example, why fully atomistic structural modelling, in this case RMC, can be so powerful even though the apparently limited information available from a diffraction pattern does not seem sufficient to obtain such detailed results.     

How wide do you want the jar?: the effect on diameter for ease of opening for wide‐mouth closures

The ease with which a container can be accessed or its ‘openability’ is becoming more of an issue for manufacturers and consumers as the average age of the population increases. Ageing brings with it a range of issues including a loss of strength and reduced dexterity. This paper aimed to look at the relationship between diameter, torque and age for standard consumer closures using a torque‐measuring device. The results of the investigation show that larger‐diameter jars (85 mm) require much higher opening forces than smaller ones (75 mm and below). Smaller jars require lower opening torques, although the force required to open many jars is still higher than many elderly people are able to generate. Copyright © 2009 John Wiley & Sons, Ltd.     

Why do organizations not learn from incidents? Bottlenecks,causes and conditions for a failure to effectively learn

If organizations would be able to learn more effectively from incidents that occurred in the past, future incidents and consequential injury or damage can be prevented. To improve learning from incidents, this study aimed to identify limiting factors, i.e. the causes of the failure to effectively learn. In seven organizations focus groups were held to discuss factors that according to employees contributed to the failure to learn. By use of a model of the learning from incidents process, the steps, where difficulties for learning arose, became visible, and the causes for these difficulties could be studied.     

Why do ecologists search for co-authorships? Patterns of co-authorship networks in ecology (1977–2016)

Scientometrics - Due to the importance of academic journals, it is critical to understand how they can create influence on research fields. An alternative way to understand how scholarly journals...     

Why do cyclists infringe at red lights? An investigation of Australian cyclists’ reasons for red light infringement

This study investigated the behavioural, attitudinal and traffic factors contributing to red light infringement by Australian cyclists using a national online survey. The survey was conducted from February to May 2010. In total, 2061 cyclists completed the survey and 37.3% reported that they had ridden through a signalised intersection during the red light phase. The main predictive characteristics for infringement were: gender with males more likely to offend than females (OR: 1.54, CI: 1.22–1.94); age with older cyclists less likely to infringe compared to younger cyclists 18–29 years (30–49 yrs: OR: 0.71, CI: 0.52–0.96; 50+ yrs: OR: 0.51, CI: 0.35–0.74), and; crash involvement with cyclists more likely to infringe at red lights if they had not previously been involved in a bicycle–vehicle crash while riding (OR: 1.35; CI: 1.10–1.65). The main reasons given for red light infringement were: to turn left (32.0%); because the inductive loop detector did not detect their bike (24.2%); when there was no other road users present (16.6%); at a pedestrian crossing (10.7%); and ‘Other’ (16.5%). A multinomial logistic regression model was constructed to examine the associations between cyclist characteristics and reasons for infringement. Findings suggest that some cyclists are motivated to infringe by their perception that their behaviour is safe and that infrastructure factors were associated with infringement. Ways to manage this, potentially risky, behaviour including behaviour programmes, more cyclist-inclusive infrastructure and enforcement are discussed.     

Why do some research articles receive more online attention and higher altmetrics? Reasons for online success according to the authors

Recent altmetrics research has started to investigate the meaning of altmetrics and whether altmetrics could reveal something about the attention or impact connected to research. This research continues this line of investigations and studies reasons for why some research has received significant online attention in one or both of two social media services; Twitter or Mendeley. This research investigated Finnish researchers’ opinions about the reasons for why their research had received significant online attention and if the attention received could reflect scientific or societal impact of their research. Furthermore it was studied whether the authors of the papers with significant online attention actively followed how their papers were shared or discussed online and if the authors thought that the online attention increased either the scientific or societal impact of their work. Based on the findings it can be stated that the level of online attention received is a sum of many factors and that there are also specific differences between the platforms where the attention has been received. For the articles that had received significant attention on Mendeley the reasons for that attention were more often seen as due to an academic audience, while the situation was reverse on Twitter, with the majority of reasons for the attention being linked to a wider audience. Similar trend could be seen when asked about whether the online attention could reflect scientific or societal impact, although a clear consensus about whether online attention could reflect any type of impact at all could not be reached.     

The hybrid proximal decomposition method applied to?the computation of a Nash equilibrium for?hydrothermal electricity markets

In this work, a decomposition method for computing a solution of a short-term hydrothermal scheduling problem is presented. An oligopolistic electricity market composed of two types of power generation units, thermal and hydroelectric, is considered. The hydroelectric units have also the possibility of pumping back water, paying in that case for the electricity consumed. The Nash equilibrium analytic condition is stated as a variational inclusion and it is shown that the associated operator has a structure suitable for decomposition, in particular by applying the variable metric hybrid proximal decomposition technique (VMHPDM). The application of VMHPDM is illustrated in several examples and numerical results for each example are presented.     

The development of ‘green’ airports: Which factors influence willingness to pay for sustainability and intention to act? A structural and mediation model analysis

The study's purpose was to determine which factors influence a consumer's willingness to pay for sustainability and their intention to take action against climate change related to airports. An expanding body of literature relates to assessing whether consumers would be willing to pay for these ‘green’ practices in the aviation industry, such as biofuels or sustainable airport construction/renovations. While previous studies have experimentally examined these scenarios, we are aware of no prior research that has proposed and assessed a structural model related to determining which factors influence consumer's perspectives on ‘green’ airports. A sample of 722 eligible participants from the United States completed the study using Amazon's Mechanical Turk. We examined future time perspective, affect toward climate change, the perceived value of sustainability, and perceptions of climate change on the endogenous variables of willingness to pay for sustainability and intentions to take action against climate change. Six of the seven hypotheses proposed were supported. Affect, perceived value, and perceptions of climate change were all significant and positively related to willingness to pay, which was positively associated with intention to act. Two non-hypothesized paths, between perceived value and future time perspective, were also positively related to intention to act. The model explained 42% of the variance in willingness to pay and 66% in intention to act. These findings offer insights into what factors significantly influence these relationships as they relate to airports. Perceived value and perceptions of climate change had the largest effect sizes in the model and were significantly related to willingness to pay and intentions to act.     

Correction to: Do Energy Resources matter for Growth Level? The dynamic effects of different strategies of renewable energy,carbon emissions on sustainable economic growth

Clean Technologies and Environmental Policy -     

The use of alpha-Al2O3:C in Risø OSL single grains attachment system for assessing the spatial dose rate distribution due to incorporation of 90Sr in human teeth

The possibility of using a single grain OSL attachment system developed by the Ris? National Laboratory (Roskilde, Denmark) for assessing the spatial distribution of radionuclides incorporated in human tissues was investigated. Detectors containing arrays of single grains of alpha-Al2O3)C powder (Landauer Inc., USA) were prepared using aluminium discs (diameter 9.7 mm), which can accommodate 100 single grains in 0.3 mm holes positioned in a 10 x 10 grid. The luminescence and dosimetric properties of each grain were investigated by exposing the detectors to uniform photon radiation fields. After the characterisation of the detectors, the systems were tested to assess the spatial dose rate distribution because of 90Sr incorporated in a tooth sample extracted from an inhabitant of the Techa River region.     

How well does I3 perform for impact measurement compared to other bibliometric indicators? The convergent validity of several (field-normalized) indicators

Scientometrics - Recently, the integrated impact indicator (I3) was introduced where citations are weighted in accordance with the percentile rank class of each publication in a set of...