Molecular group system as one energy unit

In view of the various qualifications required of materials nowadays, efforts to change the characteristics of inherent materials have continued. However, most material conversion techniques that have been used in the past, such as alloy design and doping effect, cannot overcome the limitation that properties are only added to the original characteristics of pristine materials. Therefore, herein, we introduced a new material design technique, a so-called “Molecular Group System”, which is completely different from existing methods. Since whole-set-systems are considered one-energetic-unit-system, either only the merits of the constituent elements can be emphasized or new materials completely different from the raw ones can be synthesized. In this study, block-stacking bottom-up approach was employed to form a one group system from SnO₂, SnO_x, Sn, and graphene powders, and a binder, using high-energy irradiation. Then, we discussed theoretical verifications such as SnO₂-reduction and Sn-channeling.     

Experimental behaviour of high‐strength concrete deep beams with web openings

This paper focuses on an experimental study undertaken on high‐strength concrete (HSC) deep beams with various opening sizes and locations on the web. The test covers a wide scope of variables that have not been investigated in previous research. Apart from highlighting the experimental setup, failure loads and typical crack patterns of the test specimens are also reported. Experimental results are then compared with predictions using currently available design methods. The comparison indicates that the predictions using current design methods can overly underestimate or sometimes overestimate the ultimate strength of these HSC deep beams. Further, the reduction of ultimate strengths due to the existence of web openings is not considered adequately in these design methods. To rectify the shortcomings of current design formulae, a new design equation is proposed and compared with the experimental results and those from previous studies on the related topics. The accuracy and reliability of the proposed new equation is subsequently confirmed. With the outcome of this work, more experimental tests with various opening configurations including shape and location of web openings are recommended for future study. Copyright © 2011 John Wiley & Sons, Ltd.     

Design optimization of rib/channel patterns in a PEMFC through performance heterogeneities modelling

In this paper, an approach coupling an along the channel and rib-channel models has been developed to perform a design optimization of PEM fuel cell bipolar plates rib/channel patterns. Overall performance mainly results from a competition between current collection and oxygen supply. The allows proposed to investigate the effect of geometry and operating parameters on the resulting equilibrium and optimum. Moreover, heterogeneities issued from the crushing effect by the rib on the GDL are accounted.The electrochemical parameters used in the model are fitted to experimental measurements before being used in the optimization process. Results at the channel/rib scale show the competition between the oxygen supply from the gas channel to the catalyst layer and the current collection by the ribs. This understanding is possible thanks to the access to local conditions (such as the oxygen concentration) given by the model which are difficult to reach with experimental measurements. In-plane and through plane heterogeneities of current density distribution in the catalyst layer are exhibited.Design optimization is performed on the channel width/total width ratio on the cathode side. The model suggests an optimal channel design by varying its width along the flow while the standard design considers a contant ratio. This optimal channel is shown to be mainly dependent on the stoichiometry ratio of oxygen.     

Development of functionally graded Cu–Sn–Ni/Al2O3 composite for bearing applications and investigation of its mechanical and wear behavior

This study investigates the mechanical and tribological properties of a functionally graded Cu–Sn–Ni/Al₂O₃ metal matrix composite, synthesized using horizontal centrifugal casting technique with dimension Φ_out100?×?Φ_in85?×?100?mm. The microstructure was examined along radial distances at 1, 8, and 13?mm from outer periphery. Specimens were tested for tensile strength from outer (1–8?mm) and inner zone (9–15?mm) of the casting and fractured surfaces were subjected to fractographic analysis. Wear resistance of inner layer was experimented using pin-on-disc tribometer based on Taguchi’s L₂₇ orthogonal array using three variable process parameters, such as applied loads (10, 20, and 30?N), sliding velocities (1, 2, and 3?m/s), and distances (500, 1000, and 1500?m). Optimum parameters were determined for wear rate on “smaller-the-better” basis using signal-to-noise ratio. Analysis of variance predicted the effect of each influential parameter and their interactions. Results depict that wear rate increased with load and distance, forming phases such as Cu₃Sn, Ni₃Sn, Cu₆Sn₅, etc. Worn surfaces analysis using scanning electron microscope predicted the formation of mechanically mixed layers, showing a V-trend influence of velocity on wear. Thus, fabricated composite shows the replaceability of conventional leaded bearing materials with superior copper functionally graded composites having better wear characteristics.