• Energy Research
• engineering and technology close
• 9. Industry and infrastructure close
• 14. Life underwater close

This paper studies the newly emerging wireless powered communication network (WPCN) in which one hybrid access point (H-AP) with constant power supply coordinates the wireless energy/information transmissions to/from distributed users that do not have energy sources. A "harvest-then-transmit" protocol is proposed where all users first harvest the wireless energy broadcast by the H-AP in the downlink (DL) and then send their independent information to the H-AP in the uplink (UL) by time-division-multiple-access (TDMA). First, we study the sum-throughput maximization of all users by jointly optimizing the time allocation for the DL wireless power transfer versus the users' UL information transmissions given a total time constraint based on the users' DL and UL channels as well as their average harvested energy values. By applying convex optimization techniques, we obtain the closed-form expressions for the optimal time allocations to maximize the sum-throughput. Our solution reveals "doubly near-far" phenomenon due to both the DL and UL distance-dependent signal attenuation, where a far user from the H-AP, which receives less wireless energy than a nearer user in the DL, has to transmit with more power in the UL for reliable information transmission. Consequently, the maximum sum-throughput is achieved by allocating substantially more time to the near users than the far users, thus resulting in unfair rate allocation among different users. To overcome this problem, we furthermore propose a new performance metric so-called common-throughput with the additional constraint that all users should be allocated with an equal rate regardless of their distances to the H-AP. We present an efficient algorithm to solve the common-throughput maximization problem. Simulation results demonstrate the effectiveness of the common-throughput approach for solving the new doubly near-far problem in WPCNs. 26 pages, 12 figures

Closed-loop supply chain networks are gaining research popularity due to environmental, economic and social concerns. Such networks are primarily designed to overcome carbon footprints and to retrieve end of life products from customers. This study considers a multi echelon closed-loop supply chain in the presence of machine disruption. A multi-objective model is presented to optimize the total cost, the total time and emissions in a closed-loop supply chain network. The aim is to analyze the trade-off between the objectives of cost, time, and emissions and how these decisions are impacted by the selection of different available machines. A number of solution approaches are tested on a case study from the tire industry. The results suggest the improved performance of the hybrid heuristic and the importance of controlling disruption in a closed-loop supply chain network. Furthermore, there is a trade-off between the different objective functions which can help the decision maker to choose a particular solution according to the preference of an organization. Finally, conclusion and future research avenues are provided.

Renewable energy technological innovation (RETI) is an important way to reduce carbon emissions and achieve sustainable development. Exploring whether RETI is beneficial to the improvement of carbon emission efficiency and how the market environment affects the role of RETI on carbon emission efficiency is critical to the design of effective policies. Therefore, based on the data from 25 provinces in China from 2002 to 2015, the Tobit fixed-effect model and the panel threshold model are used to investigate the impact and the mechanism of RETI on total factor carbon performance index (TCPI) from a market perspective. The results show that: (1) RETI can effectively improve TCPI, but this effect is affected by market factors; (2) With the reduction of market segmentation or the increase of market potential, the improvement effect of RETI on TCPI is significantly enhanced; (3) The panel threshold model further verifies that the impact of RETI on TCPI has a significant single threshold effect in terms of market segmentation and market potential; (4) There is an inverted "U-shaped" relationship between market segmentation and TCPI, and the increase of market potential is conducive to the improvement of TCPI. This paper provides corresponding policy implications for China to achieve the dual goals of economic transformation and carbon emission reduction.

Abstract With the rapid rise of installed nuclear power in China, meeting the increasing demands on natural uranium and rationally treating the vast spent fuel are essential issues for the sustainable development of Chinese nuclear power industry. This paper discusses four most potential nuclear fuel cycle modes in China and analyzes the natural uranium requirements under these different fuel cycle modes first based on three development patterns (low-, medium-, and high-speed) of installed nuclear power capacity. Then, an optimization model including natural uranium requirements, spent fuel final disposal amounts and total cost of electricity generation is constructed and optimization problem under two scenarios of reprocessing capacity are solved and results discussed. The annual and cumulative natural uranium requirements under these two scenarios are also calculated. Finally some conclusions are put forward based on the analyses.

Abstract This paper addresses the importance of the probabilistic analysis in determining the wave energy potential to support the design of electrical generators for wave energy conversion. The irregular activity of ocean waves induces variable frequencies and amplitudes of operation for point absorbers electrical generators, which may lead to the construction of inefficient electrical machines. Applying probabilistic models to describe the ocean wave's behavior allows the determination of the values most likely to be sampled for ocean-state parameters. Knowing these values, the most expected ocean wave potential can be determined and a proper device design can be performed. This work also refers to the importance of using the joint probability models instead of the marginal ones. Seven locations at the Portuguese coast are evaluated in order to determine their wave energy resource potential.

A generalized optimal pulsewidth modulation (PWM) technique applicable to multilevel inverters for low-switching-frequency control of medium-voltage high-power industrial ac drives is presented. Proposed synchronous optimal PWM method allows setting the maximum switching frequency to a low value without compromising the harmonic distortion of machine currents. Low switching frequency reduces the switching losses of the power semiconductor devices, resulting in higher inverter power output and efficiency. The proposed optimization results in low harmonic distortion at low switching frequency. Experimental results of a five-level inverter drive using optimal PWM are presented.

A smart gird is an emerging digital convergence technology contributing to economic and social development. With the introduction of smart grid, consumers increasingly play a critical role in the diffusion of the smart grid, and this highlights a need for examining the diffusion of the smart grid from the perspective of users. This study examines the factors influencing the adoption and diffusion of the smart grid from the perspective of users and provides some strategic guidelines for government and providers. In-depth interviews were conducted with 41 users of the smart grid in the Jeju testbed South Korea, the world’s largest community with smart grid. Data were analyzed by applying grounded theory. Nineteen categories representing factors influencing the diffusion of the smart grid were identified through open coding. Propositions integrating these factors consisted of incentives and promotions, providers’ passion and proactive attitudes, environmental and technological characteristics, continuous training and communication, and experience of economic benefits, among others. Guidelines for the successful diffusion of the smart grid in the initial stages of their introduction include conflict management, choice of appropriate technology, and authentic relationships with residents.

Abstract The quasi-static compression, three-point bending and low-speed impact behavior of E690 high-strength steel lattice corrugated sandwich panels after corrosion in a marine environment were simulated by a non-linear finite element method. The uniform corrosion model was used to calculate the effects of different levels and duration of corrosion on the bearing capacity and energy absorption of an E690 panel. The results show that the corrosion of the outer panel has the least influence on the decrease of the mechanical properties; the structure’s mechanical properties are greatly reduced by the inner panel and core corrosion, and a new deformation pattern could be observed. Considering the influence of corrosion duration, the mechanical performance ranges from bad to good: outer+inner > inner > outer. Furthermore, the difference becomes more obvious with longer corrosion times, indicating that necessary corrosion protection measures should be taken to protect the panel from corrosion in marine environment, especially for the internal part of the panel.