Optimal (r,nQ,T) batch ordering with quantized supplies

We consider the control of a single-echelon inventory installation under the (r,nQ,T) batch ordering policy. Demand follows a stationary stochastic process and, when unsatisfied, is backordered. The supply process is quantized; so the policy base batch Q needs to satisfy the constraint Q=kg, where k is an integer and q an exogenous fixed supply lot, often reflecting physical supply limitations. Assuming continuous time and a standard cost structure, we determine the (r,nQ,T) policy variables that minimize total average cost per unit time subject to the supply lot constraint. While total average cost is not convex, we show that average holding and backorders costs are jointly convex in all policy variables. This helps establish optimality properties and convex bounds that allow developing an algorithm to exactly solve the quantized supplies optimization problem. Computations reveal that, depending on the supply lot size, quantized supplies may cause serious cost increase.     

Solving multifacility Huff location models on networks using metaheuristic and exact approaches

In this paper we consider multifacility Huff facility location problem on networks. First, we introduce a slight modification of the existing mixed integer nonlinear mathematical model and confirm its validity by using the solver for nonlinear optimization, KNITRO. Second, since the problem is NP-hard, we develop three methods that are based on three metaheuristic principles: Variable Neighborhood Search, Simulated Annealing, and Multi-Start Local Search. Based on extensive computational experiments on large size instances (up to 800 customers and 100 potential facilities), it appears that VNS based heuristic outperforms the other two proposed methods.     

Computing (r, Q) policy for an inventory system with limited sharable resource

This paper deals with inventory systems with limited resource for a single item or multiple items under continuous review (r, Q) policies. For the single-item system with a stochastic demand and limited resource, it is shown that an existing algorithm can be applied to find an optimal (r, Q) policy that minimizes the expected system costs. For the multi-item system with stochastic demands and limited resource commonly shared among all items, an optimization problem is formulated for finding optimal (r, Q) policies for all items, which minimize the expected system costs. Bounds on the parameters (i.e., r and Q) of the optimal policies and bounds on the minimum expected system costs are obtained. Based on the bounds, an algorithm is developed for finding an optimal or near-optimal solution. A method is proposed for evaluating the quality of the solution. It is shown that the algorithm proposed in this paper finds a solution that is (i) optimal/near-optimal and/or (ii) significantly better than the optimal solution with unlimited resource.     

Results on rotation symmetric polynomials over GF(p)

In this paper, we generalize the recent counting results about rotation symmetric Boolean functions to the rotation symmetric polynomials over finite fields GF(p). By using Möbius function, we obtain some formulas for more general n, the number of variables. Some known formula in Boolean case are simplified.     

Pricing and inventory management in a system with multiple competing retailers under (r, Q) policies

We consider a multi-retailer system operated on an infinite horizon, in which each retailer faces stochastic demand following a Poisson process and adopts a continuous-review (r, Q) policy for replenishing inventory to satisfy customer demand. The system involves decisions of pricing and inventory management with the goal of maximizing profit, which equals the sales revenue minus the purchase and inventory costs. Taking Cournot competition into account, models are formulated to optimize simultaneously the expected sales volumes and (r, Q) policies of all retailers. An efficient approach is proposed to calculate the approximate inventory cost. Based on this approach, solution methods for centralized and decentralized scenarios are developed. A great number of numerical computations are provided to evaluate the efficiency of the solution methods, and their performance in the two scenarios. Moreover, system performance under sequential decisions (first pricing and then inventory management) is also investigated.     

基于混合需求的设施选址问题研究

研究网络中设施的需求一部分来自于网络节点, 一部分来自于过往流量的基于混合需求的设施选址问题。引入引力模型, 以新建设施获得总利润最大为目标建立非线性整数规划模型, 并构造启发式算法, 通过MATLAB进行仿真实验, 将求解结果与GPAH算法及精确算法的结果进行比较。比较结果表明, 提出的算法求解质量高、运行速度快, 可用于大中型网络设施的选址问题。     

Improved lower bound on the number of balanced symmetric functions over GF(p)

The lower bound on the number of n-variable balanced symmetric functions over finite fields GF(p) presented by Cusick et al. in [T.W. Cusick, Y. Li, P. Staˇnicaˇ, Balanced symmetric functions over GF(p), IEEE Trans. Inform. Theory 54 (3) (2008) 1304-1307] is improved in this paper. An equivalent characterization is also presented for the general case.     

Solving single-product economic lot-sizing problem with non-increasing setup cost,constant capacity and convex inventory cost in O(N log N) time

This paper considers an economic lot sizing model with constant capacity, non-increasing setup cost, and convex inventory cost function. Algorithms with computational time of O(N×TD_N)have been developed for solving the model, where N is the number of planning periods and TD_N is the total demand. This study partially characterizes the optimal planning structure of the model. A new efficient algorithm with computational time of O(N log N) has also been developed based on the partial optimal structure. Moreover, computational study demonstrates that the new algorithm is efficient.     

Thermal stability, electrical conductivity and ammonia sensing studies on p-toluenesulfonic acid doped polyaniline:titanium dioxide (pTSA/Pani:TiO2) nanocomposites

Electrically conductive p-toluenesulfonic acid (pTSA) doped polyaniline (Pani):titanium dioxide (TiO₂) nanocomposites (pTSA/Pani:TiO₂) were prepared by in situ polymerization of aniline with TiO₂ nanoparticles. Thus formed pTSA/Pani:TiO₂ nanocomposites were characterized by Fourier transform infra-red (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). The sensitivity of the nanocomposites towards low concentrations of aqueous ammonia was examined and compared with that of the pure Pani. It was found that the resistivity of pTSA doped nanocomposites increases on exposure to ammonia at room temperature. The nanocomposites were found to possess superior ammonia sensing capacity as compared to pure Pani and it showed linear relationship between the responses and the ammonia concentration. The Fourier transform infrared (FTIR) spectroscopy was used to explain the sensing mechanism. A novel mechanism for the interaction process between the sensing material and ammonia has also been proposed.     

Second order (F, α, ρ, d)-convexity and duality in multiobjective programming

A class of second order (F, α, ρ, d)-convex functions and their generalizations is introduced. Using the assumptions on the functions involved, weak, strong and strict converse duality theorems are established for a second order Mond-Weir type multiobjective dual.     

(?, T)-fuzzy rough approximation operators and the TL-fuzzy rough ideals on a ring

In this paper, we consider a ring as a universal set and study (?, T)-fuzzy rough approximation operators with respect to a TL-fuzzy ideal of a ring. First, some new properties of generalized (?, T)-fuzzy rough approximation operators are obtained. Then, a new fuzzy algebraic structure - TL-fuzzy rough ideal is defined and its properties investigated. And finally, the homomorphism of (?, T)-fuzzy rough approximation operators is studied.     

Efficiency conditions and duality models for multiobjective fractional subset programming problems with generalized (, α, , θ)-V-convex functions

In this paper, we first introduce a new class of generalized convex n-set functions, called (, α, , θ)-V-convex functions, and then present numerous sets of parametric and semiparametric sufficient efficiency conditions under generalized (, α, , θ)-V-convexity assumptions for a multiobjective fractional subset programming problem. Moreover, we construct three parametric and three semiparametric duality models and prove appropriate duality theorems.     

Electrocatalytic oxidation of methanol and other short chain aliphatic alcohols on glassy carbon electrodes modified with conductive films derived from Ni-(N,N′-bis(2,5-dihydroxybenzylidene)-1,2-diaminobenzene)

Complexes of nickel(II) with the ligand N,N′-bis(2,5-dihydroxybenzylidene)-1,2-diaminobenzene (Ni^II-DHS) can be electropolymerized onto glassy carbon surfaces in alkaline solution to give electroactive films strongly adhered on the electrode surface. In alkaline solution, these poly-[Ni^II-DHS]/GC films present the typical voltammetric response of a surface-immobilized redox couple, as can be anticipated for the Ni²⁺/Ni³⁺ transitions into the film. In addition, the films exhibit a potent and persistent electrocatalytic activity towards the oxidation of methanol. The electrocatalytic currents are, at least, 80 times higher than those obtained for the oxidation of methanol at electrodes modified with nickel hydroxide films in alkaline solutions. In addition, the current is proportional to the concentration of methanol from 0.050 to 0.30 μM. The detection limit and the sensitivity were found to be 26 ± 2 nM and 7.4 × 10⁻² ± 6 × 10⁻³ A cm² mol⁻¹ M⁻¹, respectively. Electrodes modified with poly-[Ni^II-DHS]/GC films show a moderate electrocatalytic activity towards the oxidation of other aliphatic short chain alcohols, such as: ethanol, 1-propanol, 2-propanol and n-butanol. In all cases the catalytic currents present linear dependences with the concentration of alcohol in alkaline solution. The analytical properties of these potential alcohol sensors have also been studied.     

Theoretical investigation on gas-phase reaction of CF3CH2OCH3 with OH radicals and fate of alkoxy radicals (CF3CH(O)OCH3/CF3CH2OCH2O)

Detailed theoretical investigation has been performed on the mechanism, kinetics and thermochemistry of the gas phase reactions of CF₃CH₂OCH₃ (HFE-263fb2) with OH radicals using ab-initio and DFT methods. Reaction profiles are modeled including the formation of pre-reactive and post-reactive complexes at entrance and exit channels, respectively. Our calculations reveal that hydrogen abstraction from the CH₂ group is thermodynamically and kinetically more facile than that from the CH₃ group. Using group-balanced isodesmic reactions, the standard enthalpies of formation for CF₃CH₂OCH₃ and radicals (CF₃CHOCH₃ and CF₃CH₂OCH₂) are also reported for the first time. The calculated bond dissociation energies for the CH bonds are in good agreement with experimental results. At 298 K, the calculated total rate coefficient for CF₃CH₂OCH₃ + OH reactions is found to be in good agreement with the experimental results. The atmospheric fate of the alkoxy radicals, CF₃CH(O)OCH₃ and CF₃CH₂OCH₂O are also investigated for the first time using the same level of theory. Out of three plausible decomposition channels, our results clearly point out that reaction with O₂ is not the dominant path leading to the formation of CF₃C(O)OCH₃ for the decomposition of CF₃CH(O)OCH₃ radical in the atmosphere. This is in accord with the recent report of Osterstrom et al. [CPL 524 (2012) 32] but found to be in contradiction with experimental finding of Oyaro et al. [JPCA 109 (2005) 337].     

Comment on “A direct approach with computerized symbolic computation for finding a series of traveling waves to nonlinear equations” by Engui Fan and H.H. Dai: [Comput. Phys. Commun. 153 (2003) 17]

Fan and Dai [Comput. Phys. Commun. 153 (2003) 17] have found a series of traveling wave solutions for nonlinear equations by applying a direct approach with computerized symbolic computations. They have claimed that the proposed method, in comparison with most existing symbolic computation methods such as a tanh method and Jacobi function method, not only give new and more general solutions, but also provides a guideline to classify various types of the solution according to some parameters. We show that the claims by Fan and Dai are wrong since some of the solutions do not satisfy the differential equation that they have adopted for the algebraic method.