Research on Collaborative Order Decision-Making Method for Symmetric Participants in Complex Shipbuilding Projects

More extensive enterprise cooperation is an effective means to increase the competitiveness of shipbuilding companies in the current distributed manufacturing environment. Most cross-enterprise collaborative processes for shipbuilding projects have been widely concerned. However, the symmetry and cooperativity among the order decision-making process is rarely involved. A key issue for decision makers is to balance the interests of each symmetric participant and realize the consistent decision-making for the order. Existing order decision-making methods in the shipbuilding industry are low efficiency. The aim of this paper is to provide an assistant decision-making method to support effective order decision-making and multi-party cooperation for the multi-wining negotiation objectives. To solve this problem, a collaborative order decision-making framework based on decision support system (DSS) and multi-agent system (MAS) theory is presented, simulating the collaborative order decision-making process, and bridging the order decision-making with production scheduling. Then, a multi-stage negotiation method is provided to solve the distributed and symmetric order decision-making problem, and an illustrative example is conducted to demonstrate the effectiveness and rationality of the methods. Finally, an application case using a prototype system will be reported as a result

Research on Collaborative Planning and Symmetric Scheduling for Parallel Shipbuilding Projects in the Open Distributed Manufacturing Environment

In the current distributed manufacturing environment, more extensive enterprise cooperation is an effective means for shipbuilding companies to increase the competitiveness. However, considering the project scale and the uneven production capacity between the collaborative enterprises, a key issue for shipbuilding companies is to effectively combine the product-oriented project tasks and the specialized production-oriented plants. Due to information privatization, the decision-making process of project planning and scheduling is distributed and symmetric. Existing project scheduling methods and collaboration mechanisms in the shipbuilding industry are somehow inefficient. The aim of the research is to provide an assistant decision-making method to support effective task dispatching and multi-party cooperation for better utilization of the distributed resources and to help project managers control the shipbuilding process. The article initially establishes an agent-based complex shipbuilding project collaborative planning and symmetric scheduling framework, simulating the distributed collaborative decision-making process and bridging the multi-project planning with the individual project scheduling in much detail, which fills the research gap. A negotiation method based on iterative combination auction (ICA) is further proposed to solve the integration problem of project planning and task scheduling, and an illustrative example is conducted to demonstrate the effectiveness and rationality of the methods. Finally, an application case using a prototype system on shipbuilding projects collaborative planning and scheduling will be reported as a result

Facile synthesis of Co/Pd supported by few-walled carbon nanotubes as an efficient bidirectional catalyst for improving the low temperature hydrogen storage properties of magnesium hydride

Catalytic doping is important for enhancing the hydrogen storage performance of metal hydrides, but it is challenging to develop a single catalyst to enhance both hydrogen desorption and absorption to a certain degree. Herein, a bidirectional Co/Pd catalyst, homogeneously loaded on bamboo-shaped carbon nanotubes (Co/Pd@B-CNTs), showed superior catalytic effects, improving both the hydrogen desorption and absorption properties of MgH 2 at relatively low temperatures. The MgH 2 -Co/Pd@B-CNTs composite starts to release hydrogen at 198.9 °C, which is 132.4 °C lower than as-milled MgH 2 . The hydrogen desorption activation energy for MgH 2 is reduced from 178.00 to 76.66 kJ mol -1 by the catalytic effects of Co/Pd@B-CNTs. The MgH 2 -Co/Pd@B-CNTs composite shows dramatically improved absorption kinetics; it rapidly uptakes 6.68 wt% H 2 within 10 s at 250 °C, and quickly absorbs 1.91 wt% H 2 within 100 s, even at a temperature as low as 50 °C. More importantly, a special mechanism for the bidirectional catalyst Co/Pd is proposed for the first time and discussed in detail. During the hydrogenation process, elemental Pd plays a dominant role in accelerating the preferential diffusion of hydrogen atoms at the Pd/Mg interface, while during dehydrogenation, phase transformation between Mg 2 Co and Mg 2 CoH 5 as well as a Mg-Pd alloy becomes the crucial factor, facilitating the release of hydrogen atoms by decreasing the diffusion barrier. Moreover, novel structures of bamboo-shaped carbon nanotubes with a large diameter (\u3e100 nm) and high specific surface area (146.8 m 2 g -1 ) allow the homogenous dispersion of Co/Pd NPs and enhance the direct contact with MgH 2 particles

Insights into 2D graphene-like TiO2 (B) nanosheets as highly efficient catalyst for improved low-temperature hydrogen storage properties of MgH2

© 2020 Elsevier Ltd The development of low temperature hydrogen storage system is crucial for the wide application of renewable energy. A key obstacle for this system is the lack of efficient catalysts, in which two-dimensional nanosheets have attracted considerable attention because of their unique properties. Herein, we synthesized graphene-like TiO2 (B), and applied them as a highly efficient catalyst to dramatically enhance the low temperature hydrogen storage performances of MgH2. The MgH2s–TiO2 (B) quickly absorbs 5.32 and 5.50 wt% H2 at low temperatures of 50 and 60 °C, respectively, which is superior to most of the previously catalyzed MgH2 composites. Moreover, MgH2–TiO2 (B) begins to desorb hydrogen at ~200 °C and release ~6.29 wt% H2 below 288 °C. Careful microstructure analyses reveal that TiO2 (B) nanosheets are reduced to metallic Ti nanoparticles and wrinkled Ti2O3 upon ball milling and (de)hydriding processes, which creates lots of boundary interfaces between MgH2 and Ti-based catalysts, thus facilitating the hydrogen diffusion. Besides, the in-situ formed Ti has the intermediate electronegativity between Mg and H, which could weaken the Mg–H bonds and decrease the dehydrogenation kinetic barriers. While in rehydrogenation, Ti nanoparticles act as effective heterogeneous nucleation agents of MgH2 nuclei, further promoting hydrogen absorption properties of MgH2–TiO2 (B). The present investigation provides clear evidence for remarkable catalytic effect of graphene-like TiO2 (B) on hydrogen absorption/desorption properties of MgH2, which is not only important for deeply understanding the mechanism, but also sheds lights for catalysis design towards practical low temperature hydrogen storage

The Influence of Anode Inner Contour on Atmospheric DC Plasma Spraying Process

In thermal plasma spraying process, anode nozzle is one of the most important components of plasma torch. Its inner contour controls the characteristics of plasma arc/jet, determining the motion and heating behaviors of the in-flight particles and hence influencing the coating quality. In this study, the effects of anode inner contour, standard cylindrical nozzle, and cone-shaped Laval nozzle with conical shape diverging exit (CSL nozzle) on the arc voltage, net power, thermal efficiency, plasma jet characteristics, in-flight particle behaviors, and coating properties have been systematically investigated under atmospheric plasma spraying conditions. The results show that the cylindrical nozzle has a higher arc voltage, net power, and thermal efficiency, as well as the higher plasma temperature and velocity at the torch exit, while the CSL nozzle has a higher measured temperature of plasma jet. The variation trends of the plasma jet characteristics for the two nozzles are comparable under various spraying parameters. The in-flight particle with smaller velocity of CSL nozzle has a higher measured temperature and melting fraction. As a result, the coating density and adhesive strength of CSL nozzle are lower than those of cylindrical nozzle, but the deposition efficiency is greatly improved

Synergistic catalysis in monodispersed transition metal oxide nanoparticles anchored on amorphous carbon for excellent low-temperature dehydrogenation of magnesium hydride

Magnesium hydride (MgH2) has been considered to be one of the most promising solid-state hydrogen storage materials owing to its high hydrogen capacities, excellent reversibility and abundant source. However, the high dehydrogenation energy barrier and poor kinetics embarrass the practical application of MgH2 in fuel cell. Doping nano-catalyst is deemed to be the most effective method to improve kinetics property of hydrogen storage materials, but the nanoparticles generally suffer from agglomeration and inactivation during the cycling hydrogen storage. Here we present a promising strategy to facilely prepare a high-efficiency transition metal oxide nano-catalyst, TiO2 nanoparticles, in which monodispersed single-crystal-like TiO2 nanoparticles are wrapped with amorphous carbon. The in-situ synthesized TiO2 nanoparticles/amorphous carbon catalyst exhibit superior catalytic effect on the dehydrogenation properties of MgH2. A significant reductions of hydrogen desorption temperature (163.5 °C) and activation energy (69.2 kJ mol−1) have been obtained for the TiO2 nanoparticles/amorphous carbon catalyzed MgH2, which can be fully rehydrogenated with a reversible capacity of about 6.5 wt% at 200 °C within 5 min, and then completely dehydrogenated at 275 °C within 10 min. It is demonstrated that such significantly improved hydrogen desorption properties can be attributed to the in-situ formation of TiO2 nanoparticles, amorphous carbon and multi-valance Ti species, which play the synergistically catalytic roles in the nano-catalyst. In particular, the presence of amorphous carbon in the catalyst can not only prevent the aggregation and growth of catalyst nanoparticles, but also dramatically reduce the desorption energy value of H in MgH2, according to the density functional theory calculation. This finding opens a new venue for the synthesis of monodispersed single-crystal-like TiO2 nanoparticles/amorphous carbon catalyst with high-activity, safety, low cost, and its practical application in MgH2 and other hydrogen storage systems