•Bistable and tristable mechanisms significantly improve efficiency of the point absorbers.•A multi-stable point absorber has a higher frequency bandwidth.•Robustness of the multi-stable wave energy ...device increases with respect to the damping detuning.
Here, we show that a nonlinear multi-stable system, composed of a nonlinear restoring mechanism and a linear damper-like generator, can significantly enhance the absorption efficiency of a heaving wave energy converter. This efficiency increase can be as large as few times higher than a wave energy absorber with a classical power take off system composed of a linear spring and a linear generator. Through a quantitative analysis, we also show that a nonlinear multi-stable system broadens the frequency bandwidth of the wave absorber, as well as, the bandwidth of the power take off’s damping coefficient. We propose a simple mechanical system that has the required multi-stable response upon which the investigation of this paper is based. Methodology developed and the results obtained here can be readily extended to other types of wave energy converters with one or multi degrees of freedom.
•Optimal production and carbon emission reduction (CER) rate decisions are derived.•The CER strategy cannot always benefit the environment.•Take-back legislation has different effects on environment ...in different cases.•Carbon tax and take-back legislation may not increase CER rates.
In recent years, several countries and organizations have enforced carbon tax and take-back legislation on firms, to mitigate environmental impacts. Accordingly, responsible firms have implemented remanufacturing and carbon emission reduction (CER) strategies to reduce carbon emissions. We examine the impact of carbon tax and take-back legislation on the production and CER decisions of firms. We then characterize the optimal solutions in a monopolistic environment where an integrated manufacturer is responsible for remanufacturing used-of-life products as well as producing brand-new ones, and in a competitive environment where the original equipment manufacturer (OEM) faces competition from an independent remanufacturer (IR). Subsequently, we compare and analyze the effects of carbon tax and take-back legislation on consumers and the environment under different settings. The results indicate that (i) compared with the case without CER, the CER strategy makes the IR in a competitive environment more willing to remanufacture products than the integrated manufacturer in a monopolistic environment. Additionally, the CER strategy can always increase the consumer surplus under both settings if the same remanufacturing strategy is adopted, but it cannot always benefit the environment; (ii) a higher imposed target remanufacturing level hurts (benefits) consumers in a monopolistic (competitive) environment. Moreover, it has different impacts on the environmental benefits in different scenarios; (iii) the regulations, i.e. carbon tax and take-back legislation, may not motivate firms to direct increased effort toward CER. Finally, we discuss the important insights and managerial implications for policy-makers and firms.
Objective/Hypothesis
For patients undergoing microvascular free tissue transfer (MFTT), we evaluated risk factors and financial implications of operating room (OR) take‐back procedures.
Study Design
...Retrospective review at a tertiary care center.
Methods
Patients who underwent MFTT for head and neck reconstruction from 2011 to 2018 were identified. We compared hospital length of stay and overall costs associated with OR take‐back procedures. Multivariable regression analysis evaluated factors associated with OR take‐backs during the same hospitalization.
Results
A total of 727 free flaps were reviewed, and 70 OR take‐backs (9.6%) were identified. Mean total length of stay (LOS) in the ICU was 3.4 days versus 6.7 days for non‐take‐back and take‐back flaps, respectively (P < .001). Mean total LOS on the regular floor was 6.3 days versus 13.1 days, respectively (P < .001). This resulted in a cost differential of $33,507 (94.3% increase relative to non‐take‐back flaps). The total cost associated with an OR take‐back was $39,786. Hematomas were the most common cause of take‐backs and wound dehiscence was associated with the highest costs. On multivariable analysis, higher ASA class (OR, 2.06; 95% CI, 1.11–3.99; P = .026) and shorter ischemia times (OR, 0.52; 95% CI, 0.29–0.95; P = .030) were independently associated with increased risk of take‐backs.
Conclusions
OR take‐backs infrequently occur but are associated with a significant increase in financial burden when compared to free flap cases not requiring OR take‐back. The large majority of the cost differential lies in a substantial increase of ICU and floor LOS for take‐back flaps when compared to non‐take‐back flaps.
Level of Evidence
4 Laryngoscope, 131:E1821–E1829, 2021
We investigate how corporate governance impacts firm value by comparing the value and use of cash holdings in poorly and well-governed firms. We show that governance has a substantial impact on value ...through its impact on cash: $1.00 of cash in a poorly governed firm is valued at only $0.42 to $0.88. Good governance approximately doubles this value. Furthermore, we show that firms with poor corporate governance dissipate cash quickly in ways that significantly reduce operating performance. This negative impact of large cash holdings on future operating performance is cancelled out if the firm is well governed.
This study presents an analytical framework of the product take back legislation in the context of product reuse. We characterize existing and proposed forms of E‐waste legislation and compare their ...environmental and economic performance. Using stylized models, we analyze an OEM's decision about new and remanufactured product quantity in response to the legislative mechanism. We focus on the 2012 waste electrical and electronic equipment directive in Europe, where the policy makers intended to create additional incentives for the product reuse. Through a comparison to the Original 2002 version of the directive, we find that these incentives translate into improved environmental outcomes only for a limited set of products. We also study a proposed policy that advocates a separate target for the product reuse. Our analysis reveals that from an environmental standpoint, the Recast version is always dominated either by the Original policy or by the one that advocates a separate target for product reuse. We show that the benefits of a separate reuse target scheme can be fully replicated with the aid of fiscal levers. Our main message is that there cannot be a single best environmental policy that is suitable for all products. Therefore, the consideration of product attributes is essential in identification of the most appropriate policy tool. This can be done either by the implementation of different policies on each product category or by implementation of product‐based target levels.
Background and aims
Legal regulations for dispensing in Swiss heroin‐assisted treatment were relaxed during the COVID‐19 pandemic, allowing prolonged take‐home of up to 7 days instead of two to ...reduce patient contact and the risk of infection. Our study aimed to measure the consequences of this new practice.
Design, setting and participants
This was a retrospective cohort study set in Switzerland’s largest outpatient centre for opioid agonist therapy. One hundred and thirty‐four (72.4%) of the 185 patients receiving oral diacetylmorphine (DAM) participated in the study.
Measurements
Through the utilization of electronic medication prescription and dispensing software, as well as the electronic medical record, the following data were extracted to explore the potential consequences: dose of DAM, the number of antibiotic therapies, emergency hospitalizations and incarcerations. Age, gender, prescriptions for psychotrophic drugs and additional prescription for injectable DAM were tested to assess an increased risk of losing prolonged take‐home privileges. Data in the year since prolonged take‐home (period 2) were compared with data from the equivalent prior year (period 1).
Findings
DAM take‐home was not associated with a change in DAM dose (P = 0.548), the number of emergency hospitalizations (P = 0.186) or the number of incarcerations (P = 0.215); 79.1% of all patients were able to maintain their extended take‐home privileges. However, patients who had injectable DAM experienced significant reductions in their prolonged take‐home privileges.
Conclusion
Allowing patients to take home oral diacetylmorphine for up to 7 days as treatment for opioid use disorder does not appear to pose any demonstrable health risk. It is generally manageable for the large majority of patients. However, careful consideration of prolonged take‐home for patients with additional injectable diacetylmorphine is recommended, as these patients are more likely to lose take‐home privileges.
The wave energy sector has made and is still doing a great effort in order to open up a niche in the energy market, working on several and diverse concepts and making advances in all aspects towards ...more efficient technologies. However, economic viability has not been achieved yet, for which maximisation of power production over the full range of sea conditions is crucial. Precise mathematical models are essential to accurately reproduce the behaviour, including nonlinear dynamics, and understand the performance of wave energy converters. Therefore, nonlinear models must be considered, which are required for power absorption assessment, simulation of devices motion and model-based control systems. Main sources of nonlinear dynamics within the entire chain of a wave energy converter - incoming wave trains, wave-structure interaction, power take-off systems or mooring lines- are identified, with especial attention to the wave-device hydrodynamic interaction, and their influence is studied in the present paper for different types of converters. In addition, different approaches to model nonlinear wave-device interaction are presented, highlighting their advantages and drawbacks. Besides the traditional Navier-Stokes equations or potential flow methods, ‘new’ methods such as system-identification models, smoothed particle hydrodynamics or nonlinear potential flow methods are analysed.
This paper is dedicated to solving the k-winners-take-all problem with large-scale input signals in a distributed manner. According to the decomposition of global input signals, a novel dynamical ...system consisting of multiple coordinated neural networks is proposed for finding the k largest inputs. In the system, each neural network is designed to tackle its available partial inputs only for a local objective ki (ki≤k). Simultaneously, a consensus-based approach is adopted to coordinate multiple neural networks for achieving the global objective k. In addition, an inertial term is introduced in each neural network for regulating its transient behavior, which has the potential of accelerating the convergence. By developing a cocoercive operator, we theoretically prove that the multiple neural networks with inertial terms converge asymptotically/exponentially to the k-winners-take-all solution exactly from arbitrary initial states for whatever decomposition of inputs and objective. Furthermore, some extensions to distributed constrained k-winners-take-all are also investigated. Finally, simulation results are presented to substantiate the effectiveness of the proposed system as well as its superior performance over existing distributed networks.
Ocean wave energy is attractive for its large reserves, exploitability and low emissions. Although many Wave Energy Converter (WEC) concepts have been proposed, high construction cost hinders the ...engineering application of WECs. Similar challenges arise in the applications of floating breakwaters. The construction cost can be reduced by combining different structures as one integrated system which has the advantage of cost-sharing, space-sharing and multi-functionality. This integrated design approach has stimulated the rapid development of the hybrid system combining floating breakwaters and WECs in recent years. The novel floating breakwater-WEC system is often classified as a wave-energy-utilizing type floating breakwater. The different approaches for integrating floating breakwaters and WECs are summarized in this review. The hydrodynamic performance and power take-off performance of these hybrid floating breakwater-WEC systems are the focus of this review. The insights gained from previous studies of this kind of system and the potential challenges for further developments of this technology are also provided. The cost-sharing and multi-function of the breakwater-WEC system can help facilitate the engineering application of the floating breakwaters and WECs.
•The researches and developments of the hybrid floating breakwater-WEC systems were reviewed thoroughly.•The pros and cons of various types of the hybrid floating breakwater-WEC systems were specified.•The insight and the potential challenges for further developments of this hybrid system are provided.
•A self-powered smart point-absorber wave energy converter is designed.•The kinematic and dynamic models of the system with the flywheel are established.•The maximum output power of the system in the ...dry experiment is 5.67 W.•The maximum and average mechanical efficiency are 66.63 % and 48.35 %, respectively.•The wave condition monitoring based on deep learning algorithms was implemented.
Self-powered smart buoys are widely used in sustainable sea, such as marine environmental monitoring. The article designs a self-powered and self-sensing point-absorber wave energy converter based on the two-arm mechanism. The system consists of the wave energy capture module, the power take-off module, the generator module and the energy storage module. As the core component of the wave energy converter, the power take-off module is mainly composed of a two-arm mechanism, which can convert the oscillation heave motion into unidirectional rotary motion. To evaluate the power generation performance of the system, the kinematic and dynamic models of the wave energy converter with the flywheel are established, and the disengagement and engagement phenomena of the flywheel are analyzed. The effectiveness of the prototype in capturing wave energy is verified through dry experiments in lab and field tests. The dry experiment reveals that the maximum output power of the system is 5.67 W, and the maximum and average mechanical efficiency are 66.63 % and 48.35 %, respectively. Additionally, the field test demonstrates that the peak output power can reach 92 W. Meanwhile, the generated electrical signals can be processed by deep learning algorithms to accurately identify different wave states. This high performance confirms that the proposed wave energy converter can meet its own energy needs by capturing wave energy in the marine environment, while also achieving self-sensing for wave condition monitoring. The system has great potential for promoting the development of intelligent sustainable sea in the future.
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