SELF-ASSEMBLED METAL ATOM CHAINS ON GRAPHENE NANORIBBONS

Electronic and magnetic properties of alkali and alkaline-earth metal doped graphene nanoribbons (GNRs) are studied by the pseudopotential density functional method. Strong site dependence is observed in metal adsorption on GNRs, and the adsorbed metal atoms are found to spontaneously form atomic chains in a particular form of GNRs. Such doped GNRs exhibit intriguing magnetic properties such as hysteresis and spin compensation as metal atoms switch from one edge to another at alternating gate voltages. Our study shows that the metal atoms can be used as reagents that can identify the edge atomic structures of GNRs and also as gate-driven spin valves that control the spin current in GNRs.X1170sciescopu

ELECTRONIC PROPERTY OF NA-DOPED EPITAXIAL GRAPHENES ON SIC

The electronic property of epitaxial graphenes with Na adsorption or intercalation is studied with the use of pseudopotential density functional method. It is found that the charge transfer and the Na binding energy show strong coverage dependence. Calculated energetics shows that Na prefers the intercalation between the buffer and top graphene layers to the adsorption on top graphene layer. The buffer layer is inert to Na adsorption on top graphene layer but it is charged when Na atoms are intercalated. This indicates that the conduction of epitaxial graphenes can be affected significantly by Na intercalation.X1119sciescopu

Quantity discount contract for supply chain coordination with false failure returns

Consumer return attracts more and more academic attention due to its rapidly expanding size, and a large portion of it falls into the category of false failure return, which refers to return without functional defect. In this paper, we exclusively consider profit results from exerting costly effort to reduce false failure returns in a reverse supply chain consisting of a retailer and a supplier. The supply chain as a whole has strong incentive to reduce false failure returns because it can avoid much reprocessing cost associated. But typically, retailers enjoy a full credit provided by suppliers in case of returns, and hence they may not have sufficient incentives to exert enough effort for supply chain profit maximization. In some scenarios they may even have the motivation to actually encourage such returns. We suggest using a coordination contract to resolve such profit conflicts. The contract we propose is a quantity discount contract specifying a payment to the retailer with an amount exponentially decreasing in the number of false failure returns. We give explicit forms of such contracts given different assumptions about distribution of the number of returns and we also prove that such contract is capable of increasing both retailer's and supplier's profit simultaneously. Besides, when the contract is used together with other forward supply chain coordination contracts in a closed-loop chain, it is shown that it can act to deter retailer's potential incentive to encourage false failure returns. Moreover, some modifications of the contract may lead to easy allocation of incremental profit within the supply chain. © 2010 IEEE.published_or_final_versionThe 6th International Conference on Natural Computation (ICNC 2010), Yantai, Shandong, China, 10-12 August 2010. In Proceedings of the International Conference on Natural Computation, 2010, v. 8, p. 4450-445

Inducing optimal service capacities via performance-based allocation of demand in a queueing system with multiple servers

Theme: Soft Computing Techniques for Advanced Manufacturing and Service SystemsIn this paper, we study the use of performance-based allocation of demand in a multiple-server queueing system. The same problem with two servers have been studied in the literature. Specifically, it has been proposed and proved that the linear allocation and mixed threshold allocation policies are, respectively, the optimal state-independent and state-dependent allocation policy in the two-server case. The multiple-server linear allocation has also been shown to be the optimal state-independent policy with multiple servers. In our study, we focus on the use of a multiple-server mixed threshold allocation policy to replicate the demand allocation of a given state-independent policy to achieve a symmetric equilibrium with lower expected sojourn time. Our results indicate that, for any given multiple-server state-independent policy that prohibits server overloading, there exists a multiple-server mixed threshold policy that gives the same demand allocation and thus have the same Nash equilibrium (if any). Moreover, such a policy can be designed so that the expected sojourn time at a symmetric equilibrium is minimized. Therefore, our results concur with previous two-server results and affirm that a trade-off between incentives and efficiency need not exist in the case of multiple servers.published_or_final_versionThe 40th International Conference on Computers and Industrial Engineering, (CIE 2010), Hyogo, Japan, 25-28 July 2010. In Proceedings of the International Conference on Computers & Industrial Engineering, 2010, p. 1-

Incentive effects of common and separate queues with multiple servers: The principal-agent perspective

A two-server service network has been studied by Gilbert and Weng [13] fromthe principal-agent perspective. In the model, services are rendered by twoindependent facilities coordinated by an agency. The agency must devise astrategy to allocate customers to the facilities and determine the compensation.A common queue allocation scheme and separate queue allocation scheme are thencompared. It has been shown that the separate queue system gives morecompetition incentives to the independent facilities and induces a higherservice capacity. The main aim of this paper is to extend the results of thetwo-server queueing model to the case of multiple-server queueing model. Ouranalysis shows that in the case of multiple servers the separate queueallocation scheme creates more competition incentives for servers to increasetheir service capacities. In particular, when there are not severe diseconomiesassociated with increasing service capacity, the separate queue allocationscheme gives a lower expected sojourn time in equilibrium. © 2009 IEEE.published_or_final_versionProceedings of the 39th International Conference on Computers and Industrial Engineering (CIE39), Troyes, France, 6-8 July 2009, p. 1249-125

Minimizing equilibrium expected sojourn time via performance-based mixed threshold demand allocation in a multiple-server queueing environment

We study the optimal demand allocation policies to induce high service capacity and achieve minimum expected sojourn times in equilibrium in a queueing system with multiple strategic servers. We propose the mixed threshold allocation policy as an optimal state-dependent policy that induces optimal service capacity from strategic servers. Compensation to the server can be paid at customer allocation or upon job completion. Our study focuses on the use of a multiple-server mixed threshold allocation policy to replicate the demand of a given state-independent policy to achieve a symmetric equilibrium with lower expected sojourn time. The results indicate that, under both payment schemes, for any given multiple-server state-independent policy, there exists a multiple-server threshold policy that produces identical demand allocation and Nash equilibrium (if any). Moreover, the policy can be designed to minimize the expected sojourn time at a symmetric equilibrium. Further-more, under the payment-at-allocation scheme, our results, combining with existing results on the optimality of the multiple-server linear allocation policy, show that the mixed threshold policy can achieve the maximum feasible service capacity and thus the minimum feasible equilibrium expected sojourn time. Hence, our results agree with previous two-server results and affirm that a trade-off between incentives and efficiency need not exist in the case of multiple servers.published_or_final_versio

On improving incentive in a supply chain: Wholesale price contract vs quantity dependent contract

Theme: Soft Computing Techniques for Advanced Manufacturing and Service SystemsIn this paper, we first study the performance of a supply chain consisting of one retailer and one supplier. The supplier sets the price scheme of some goods and the retailer then decides the order level and sells the goods in the market. Specifically, a quadratic cost function is assumed here to approximate the U-shape cost curve commonly observed in industries. Two kinds of contracts offered by the supplier are investigated, namely wholesale price contract and quantity dependent contract. Wholesale price is fixed under the first contract but varies depending on order level under the second one. We show that certain wholesale price contract successfully induces the retailer to order at a level such that supply chain profit is maximized, but extra cost in implementation may occur due to supplier's disagreement on this price. Given this, we propose an efficiency measure to show to what extent the wholesale price contract helps to increase supply chain profit. For quantity dependent contract, we show that it can coordinate the supply chain and leads to a proportional division of supply chain profit. We then generalize the analysis to cover the case of multiple retailers and single supplier where similar results are also obtained.published_or_final_versionThe 40th International Conference on Computers and Industrial Engineering, (CIE 2010), Hyogo, Japan, 25-28 July 2010. In Proceedings of the International Conference on Computers & Industrial Engineering, 2010, p. 1-

Plasmonic colloidal nanoparticles with open eccentric cavities via acid-induced chemical transformation

Surface-enhanced Raman spectroscopy (SERS) has been considered a promising technique for the detection of trace molecules in biomedicine and environmental monitoring. The ideal metal nanoparticles for SERS must not only fulfill important requirements such as high near-field enhancement and a tunable far-field response but also overcome the diffusion limitation at extremely lower concentrations of a target material. Here, we introduce a novel method to produce gold nanoparticles with open eccentric cavities by selectively adapting the structure of non-plasmonic nanoparticles via acid-mediated surface replacement. Copper oxide nanoparticles with open eccentric cavities are first prepared using a microwave-irradiation-assisted surfactant-free hydrothermal reaction and are then transformed into gold nanoparticles by an acidic gold precursor while maintaining their original structure. Because of the strong near-field enhancement occurring at the mouth of the open cavities and the very rough surfaces resulting from the uniformly covered hyperbranched sharp multi-tips and the free access of SERS molecules inside of the nanoparticles without diffusion limitation, adenine, one of the four bases in DNA, in an extremely diluted aqueous solution (1.0 pM) was successfully detected with excellent reproducibility upon laser excitation with a 785-nm wavelength. The gold nanoparticles with open eccentric cavities provide a powerful platform for the detection of ultra-trace analytes in an aqueous solution within near-infrared wavelengths, which is essential for highly sensitive, reliable and direct in vivo analysis.None1132sciescopu

The anomalous U(1) global symmetry and flavors from an SU(5) x SU(5)′' GUT in Z12−IZ_{12-I} orbifold compactification

In string compactifications, frequently there appears the anomalous U(1) gauge symmetry which belonged to E8$\times$E8 of the heterotic string. This anomalous U(1) gauge boson obtains mass at the compactification scale, just below $10^{18\,}$GeV, by absorbing one pseudoscalar (corresponding to the model-independent axion) from the second rank anti-symmetric tensor field $B_{MN}$. Below the compactification scale, there results a global symmetry U(1)$_{\rm anom}$ whose charge $Q_{\rm anom}$ is the original gauge U(1) charge. This is the most natural global symmetry, realizing the "invisible" axion. This global symmetry U(1)$_{\rm anom}$ is suitable for a flavor symmetry. In the simplest compactification model with the flipped SU(5) grand unification, we calculate all the low energy parameters in terms of the vacuum expectation values of the standard model singlets.Comment: 18 pages, 4 figur