Collaboration in the offshore wind farm decommissioning supply chain

The purpose of this study is to explore how actors in the offshore wind farm decommissioning supply chain collaborate to manage collective uncertainties—external supply chain uncertainties shared among several supply chain actors. Semi-structured expert interviews with ten companies active in five different segments of the decommissioning supply chain in the Netherlands, Germany, and Belgium are conducted. Businesses currently utilize collaborative communication, information sharing, and joint knowledge creation to mitigate the adverse effects of collective uncertainties. However, collaboration is severely impeded by the presence of barriers such as intellectual property or the lack of resources. Nevertheless, opportunities to lower these hurdles and improve collaboration across the supply chain exist. This study contributes to the literature on collective uncertainties and supply chain collaboration in offshore wind decommissioning. Additionally, this paper provides practitioner-oriented insights to leverage supply chain collaboration in dealing with the decommissioning challenge

Miniature photonic-crystal hydrophone optimized for ocean acoustics

This work reports on an optical hydrophone that is insensitive to hydrostatic pressure, yet capable of measuring acoustic pressures as low as the background noise in the ocean in a frequency range of 1 Hz to 100 kHz. The miniature hydrophone consists of a Fabry-Perot interferometer made of a photonic-crystal reflector interrogated with a single-mode fiber, and is compatible with existing fiber-optic technologies. Three sensors with different acoustic power ranges placed within a sub-wavelength sized hydrophone head allow a high dynamic range in the excess of 160 dB with a low harmonic distortion of better than -30 dB. A method for suppressing cross coupling between sensors in the same hydrophone head is also proposed. A prototype was fabricated, assembled, and tested. The sensitivity was measured from 100 Hz to 100 kHz, demonstrating a minimum detectable pressure down to 12 {\mu}Pa (1-Hz noise bandwidth), a flatband wider than 10 kHz, and very low distortion

The data-driven newsvendor problem:Achieving on-target service-levels using distributionally robust chance-constrained optimization

The classical approach to the newsvendor problem is to first estimate the demand distribution (or assume it to be given) and then determine the optimal inventory level. Data-driven optimization offers an alternative, where the inventory level is determined directly from the data. In this paper, we consider the data-driven newsvendor problem under a service-level constraint. We show that existing approaches to this problem suffer from overfitting, resulting in service-levels that are below the target service-level. We propose new data-driven approaches and corresponding mathematical optimization models based on methods of distributionally robust chance-constrained optimization—which have not yet been applied and empirically tested in the context of the data-driven newsvendor problem. We assess the effectiveness of our approaches by means of an extensive numerical study. To that end, we conduct structured experiments based on simulation as well as experiments based on a real-life bikesharing system where we consider the daily usage data along with information on weather and seasonal factors. The results demonstrate that our methods achieve on-target service-levels even in absence of large amounts of data. All in all, our study provides ample empirical evidence that distributionally robust chance-constrained optimization is a viable approach for addressing the data-driven newsvendor problem

A share-first-plan-second policy for efficient cooperation in a multi-modal transportation corridor

Cooperation in transportation networks has been a cornerstone of policies towards more sustainable transportation, aiming to improve the modal split and increase the fill rates of transportation resources. Effective cooperation between transportation firms requires some form of joint planning, which is often challenging to implement from an IT perspective and difficult to sustain due to the reliance on advanced planning software. In this paper, we present a simple but effective policy for cooperative transportation that does not require a complex joint optimization of operations. In this share-first-plan-second policy, cooperating firms first develop a cyclic schedule for a fleet of shared transportation resources and then assign their shipments to the transportation resources in real time. The policy performs nearly as well as a jointly optimized planning of operations while not requiring advanced IT systems and planning software. Finally, the share-first-plan-second policy exhibits robustness against deviations from planned transport operations, enhancing its practical applicability

Order acceptance in food processing systems with random raw material requirements

This study considers a food production system that processes a single perishable raw material into several products having stochastic demands. In order to process an order, the amount of raw material delivery from storage needs to meet the raw material requirement of the order. However, the amount of raw material required to process an order is not exactly known beforehand as it becomes evident during processing. The problem is to determine the admission decisions for incoming orders so as to maximize the expected total revenue. It is demonstrated that the problem can be modeled as a single resource capacity control problem. The optimal policy is shown to be too complex for practical use. A heuristic approach is proposed which follows rather simple decision rules while providing good results. By means of a numerical study, the cases where it is critical to employ optimal policies are highlighted, the effectiveness of the heuristic approach is investigated, and the effects of the random resource requirements of orders are analyzed

Hypertension and obesity in cardiology outpatients: a cross-sectional study

Introduction: Atherosclerotic cardiovascular diseases are the leading causes of death worldwide. Both hypertension and obesity are frequent in Turkey and are seen in around 30% of the population. This study aimed to determine the prevalence of hypertension and to investigate its relationship with obesity in patients admitted to a cardiology outpatient clinic. Methods: This descriptive cross-sectional study was conducted between the 15th of January and the 28th of February 2018 at the Medical Park İzmir Hospital Cardiology Polyclinics. Data were collected from 55 out of 256 people who were referred to the clinic on the specified dates. Data were collected about systolic and diastolic blood pressures, height, weight, gender, age category, educational status, marital status, and history of hypertension. Results: Of the participants, 35 (63.6%) were men, and 20 (36.4%) were women. The mean age and body mass index values were 44.60±11.03and 28.18±3.89kg/m2, respectively. In total, 85.4% were overweight or obese. The mean systolic and diastolic blood pressures were 140.09±7.99 mmHg and 90.69±7.07 mmHg, respectively. 31 (56.4%) patients had systolic, 34 (61.8%) had diastolic, and 37 (67.3%) had systolic or diastolic hypertension. Of those with hypertension, 26 (70.2%) were not aware of their condition. In the regression analysis, gender was the only independent factor predicting high blood pressure (p=0.005; odds ratio=6.4). Conclusion: Hypertension and obesity were common among patients in the cardiology outpatient clinics. Family physicians are expected to be competent in managing common health problems and are focused on preventive health practices, and thus, they should take a more active role in the struggle against hypertension and obesity