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Hexagonal boron nitride (h-BN) is an electrical insulator with a large band gap of 5 eV and a good thermal conductor of which melting point reaches about 3000 °C. Due to these properties, much attention was given to the thermal stability rather than the electrical properties of h-BN experimentally and theoretically. In this study, we report calculations that the electronic structure of monolayer h-BN can be influenced by the presence of a vacancy defect which leads to a geometric deformation in the hexagonal lattice structure. The vacancy was varied from mono- to tri-vacancy in a supercell, and different defective structures under the same vacancy density were considered in the case of an odd number of vacancies. Consequently, all cases of vacancy defects resulted in a geometric distortion in monolayer h-BN, and new energy states were created between valence and conduction band with the Fermi level shift. Notably, B atoms around vacancies attracted one another while repulsion happened between N atoms around vacancies, irrespective of vacancy density. The calculation of formation energy revealed that multi-vacancy including more B-vacancies has much lower formation energy than vacancies with more N-vacancies. This work suggests that multi-vacancy created in monolayer h-BN will have more B-vacancies and that the presence of multi-vacancy can make monolayer h-BN electrically conductive by the new energy states and the Fermi level shift.

In a recent paper, Mishra and Raghunathan (Mishra, B. K., S. Raghunathan. 2004. Retailer- vs. vendor-managed inventory and brand competition. Management Sci. 50(4) 445–457) claimed that retailers prefer vendor-managed inventory (VMI) because it restores competition among manufacturers and encourages them to maintain a higher stock of their own brand under VMI than would be maintained under retailer-managed inventory (RMI). This paper shows that these results do not hold in general: each manufacturer's stocking level may be higher under RMI than under VMI and the retailer may lose by adopting VMI depending on the profit margin of the retailer relative to that of the manufacturers, the magnitude of the holding costs, and the intensity of brand competition. Numerical examples show that the effect of brand competition on the system is not so significant and the transfer of holding cost to the vendor is the key incentive for the retailer's adoption of VMI.

Abstract:In the apparel industry, vendors often suffer from high mismatches in supply and demand. To cope with this problem, they procure the same style product from different suppliers with different manufacturing costs. Especially in the quick response environment, which allows vendors to monitor trends in customer demand and search for available suppliers through the electronic market, they have additional opportunities to improve their decision-making. In this paper, we propose an analytical profit maximization model and develop efficient decision tools to help both the middle and lower level managers pursuing this strategy. Furthermore, we have shown how significantly the vendors' potential competitive edge can be improved by exploiting multiple supply options, even at the expense of high premium procurement costs for late orders. The effect is critical, especially in a highly competitive market, and it has important implications for the top managers.

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