Browsing by Author "Liu, M."
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Item Facile Synthesis of Pd-Ir Bimetallic Octapods and Nanocages Through Galvanic Replacement and Co-Reduction, and their use for Hydrazine DecompositionLiu, M.; Zheng, Y.; Xie, S.; Li, N.; Lu, Ning; Wang, Jinquo; Kim, Moon J.; Guo, L.; Xia, Y.This article describes a facile synthesis of Pd-Ir bimetallic nanostructures in the forms of core-shell octapods and alloyed nanocages. The success of this synthesis relies on the use of Pd nanocubes as the sacrificial templates and interplay of two different processes: the galvanic replacement between an Ir precursor and the Pd nanocubes and the co-reduction of Pd²⁺ and Ir³⁺ by ethylene glycol. The galvanic replacement played a dominant role in the initial stage, through which Pd atoms were dissolved from the side faces whereas Ir atoms were deposited at the corner sites to generate Pd-Ir core-shell octapods. As the concentration of Pd²⁺ in the reaction mixture was increased, co-reduction of Pd²⁺ and Ir³⁺ occurred in the late stage of synthesis. The resultant Pd and Ir atoms were deposited onto the octapods while the Pd atoms in the interiors continued to be etched away due to the galvanic replacement, finally leading to the formation of Pd-Ir alloyed nanocages. The octapods and nanocages were then evaluated as catalysts for the selective generation of hydrogen from the decomposition of hydrous hydrazine. The nanocages exhibited better selectivity for hydrogen generation than octapods (66% versus 29%), which can be attributed to the presence of an alloyed, porous structure on the surface.Item Impact of Power Structures in a Subcontracting Assembly System(Springer New York LLC) Li, G.; Li, L.; Liu, M.; Sethi, Suresh P.; Sethi, Suresh P.We investigate the impact of power structures on the production and pricing strategies in a decentralized subcontracting assembly system consisting of two suppliers (key supplier and subcontractor) and one manufacturer (assembler). The key supplier, who is also the general contractor, negotiates with the manufacturer and assigns partial component production to the subcontractor. We first identify a single power regime (SPR), in which either the key supplier or the manufacturer determines the wholesale price or the order/production quantity. Under SPR, we consider three power structures, namely, KSA, KAS, and SKA. We find that the assembly system will substantially benefit under KAS. Results show that the subcontracting mechanism between the two suppliers can increase each firm’s profit and disperse the bargaining power. Such a decentralization of powers can weaken the horizontal decentralization between the suppliers and improve the system’s performance, thereby achieving a win–win situation. Furthermore, we extend our analysis to a dual power regime (DPR), in which the key supplier or the manufacturer decides on price and quantity. We show that the proposed assembly system performs optimally under DPR. Moreover, the system will benefit if the firm that is substantially near the end market makes the centralization decision. Compared with the classical pull and push contract model, the proposed assembly system provides the best performance under DPR. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.Item Numerical Study on Uniform-Shear Flow over a Circular Disk at Low Reynolds Numbers(American Institute of Physics Inc.) Yang, J.; Liu, M.; Wang, C.; Zhu, Xiaowei; Zhang, A.; Zhu, XiaoweiUniform shear flows over a circular disk of aspect ratio 10 (thickness/diameter) at low Reynolds numbers are numerically investigated with the main focus on the effect of inlet shear on the wake evolutions. The Reynolds numbers considered are Re = 140, 160, and 180 based on the inlet center velocity uc and disk diameter d. The non-dimensional shear rate k(= |V̅u|d/u_c) is varied from 0 to 0.09. The bifurcations leading to unsteady states with hairpin vortex shedding occur much earlier in uniform shear. In most cases, wake evolutions occurring as the shear rate increases in uniform shear are similar to those as the Reynolds number increases in uniform flow. A new wake mode termed as dragonfly-wings (DW) mode is captured at Re = 180 and k = 0.01 and 0.03. At DW mode, hairpin vortex structures are shed from diametrically opposite orientations, but with irregularity in strength and shape, i.e., three different vortex loops are observed in the wake, and produce three peaks at low frequencies in the frequency spectrum of the drag. The planar-symmetry plane for standing-wave and zig-zig modes is determined by both the initial conditions and the direction of the uniform shear. It is found that with increasing inlet shear rate, the non-dimensional shedding frequency remains nearly constant for the low shear rates (k < 0.1). Time-averaged drag and lift coefficients slightly increase with increasing inlet shear rate. Finally, the hysteretic property of the DW mode transition is examined and further investigated using the Landau mode, indicating that DW mode transition is non-hysteretic (supercritical). ©2018 Author(s).Item Online Market Entry and Channel Sharing Strategy with Direct Selling Diseconomies in the Sharing Economy Era(Elsevier B.V., 2019-05-16) Li, G.; Zhang, X.; Chiu, S. -M; Liu, M.; Sethi, Suresh P.; Sethi, Suresh P.Channel sharing is an important marketing strategy for giant retailers who sell their own store brands and resell national brands for cooperative manufacturers simultaneously. To expand their market and increase profitability, national brand manufacturers may consider entering the online market through direct selling. To counter such threats, retailers may adopt a channel sharing strategy on whether to terminate the national brand product-reselling business. We analyze three scenarios, namely, the base scenario (the retailer sells both brands), the dual channel scenario (the manufacturer enters the online market while the retailer sells both brands), and the termination scenario (each firm sells their own brand because of the retailer's termination of the reselling business) to investigate the strategic interactions between the retailer and the manufacturer. We find that the termination of channel sharing by the retailer is an ineffective threat to prevent the manufacturer from entering the online market when the direct selling diseconomy is relatively low; otherwise, the effectiveness of the retailer's threat hinges on the store brand's quality. Specifically, the retailer's threat is valid if the store brand products' quality is low, whereas such threat is invalid if the store brand's quality is high. Interestingly, our results also reveal that the retailer's profit suffers “a cliff-like drop” in the store brand's quality level. This finding suggests that selling a higher quality store brand may hurt the retailer's profit once the store brand's quality exceeds a certain threshold. ©2019 Elsevier B.V.