Binary decision rules for multistage adaptive mixed-integer optimization

Mathematical Programming - Decision rules provide a flexible toolbox for solving computationally demanding, multistage adaptive optimization problems. There is a plethora of real-valued decision...     

Polymerization of allyldimethyldodecylammonium bromide in micellar and isotropic media

To study the effect of micellar aggregation upon polymerization and polymer products, the polymerization of the micelle forming monomer allyldimethyldodecylammonium bromide (I) was investigated under both micellar and isotropic conditions. NMR spectroscopy and fluorescence quenching were employed to elucidate the structural characteristics and molecular weight of the polymer obtained by γ-ray irradiation. It was found that (I) undergoes effective polymerization in the micellar state, producing a polymer which consists of a mixture of head to tail and head to head configurations at the ratio 85/15, and has a mean molecular weight of 11,000 ± 1000 daltons.     

New insights into ethene epoxidation on two oxidized Ag[111] surfaces

Reaction mechanisms and activation energies for the complete conversion of ethene to ethene epoxide on two recently characterized oxidized Ag{111} surfaces have been determined from density functional theory. On both surfaces, epoxidation proceeds through a two-step nonconcerted mechanism via an oxametallacycle intermediate. The key implications are that both surfaces are active and that epoxidation can take place over a wide O coverage regime.     

Reconfiguration of carrier assignment in cellular networks

We consider the problem of updating nominal carrier assignments in cellular networks, which dymamically operate with channel borrowing and reassignments, to match the timevarying offered traffic demands encountered on these systems. Assuming an existing assignment of nominal carriers and the new requirements in each cell, we formulate the problem of obtaining a new assignment such that the number of carriers required to meet the total traffic demand as well as the number of different assignments between the old and the new allocation are minimized. We introduce two approaches to obtain this new assignment. One approach treats the two objectives independently and is applicable to problems with cochannel interference constraints only. This approach produces a new assignment optimized with respect to the first goal, and then rearranges the frequencies of this new allocation so that the number of different assignments with respect to the previous allocation is minimum. A second approach aims at satisfying both goals at the same time and is applicable to problems with any type of interference constraints. The main advantage of this approach is the introduction of a single window parameter which can control the assignments produced, by favoring one goal at the expense of the other. We study several transition scenarios in macrocellular and microcellular environments, and show that in the majority of cases these objectives are conflicting, and that reconfiguration strongly depends on the amount of change of the traffic requirements.     

Effects of metal irises on the guided-mode properties in asymmetrical slab waveguides

The diffraction phenomenon caused by metal transverse irises placed into an asymmetrical slab waveguide is examined by using the integral equation method. We concentrate on the possibility of controlling the radiation characteristics of the structure by changing the irises positions and the slab waveguide asymmetry. The aperture electric-field distribution is expressed in terms of a finite series of Chebyshev polynomials. The dominant TE guided-mode reflection and transmission coefficients, the near-field distribution and the far-field radiation pattern are calculated, while numerical results are presented for several cases of asymmetrical slab waveguides and different irises’ positions.     

Simplified method for concentration of mitochondrial membrane protein complexes

Extracting and concentrating mitochondrial protein complexes from gel strips after blue native PAGE (BN‐PAGE) can be daunting tasks using the traditional methods, such as electroelution, passive diffusion and centrifugal concentration. We present a simplified gel electrophoresis method to concentrate mitochondrial protein complexes with excellent recovery rate. Mitochondrial complex I present in a long gel strip from BN‐PAGE can be easily concentrated into a 0.8 cm gel strip when a second BN‐PAGE is performed with a Y‐shaped gel and the addition of 0.01% n‐dodecyl β‐D ‐maltoside and 0.001% SDS in the cathode buffer. Once completed, the concentrated protein complex in the gel strip is ready for SDS‐PAGE or proteomic studies.     

A Cross Layer Scheduling Framework for Supporting Bursty Data Applications in WCDMA Networks

In future wireless networks multimedia applications are expected to finally dominate the overall traffic volume. Shared channels are more suitable for the transmission of this type of traffic, as they are able to periodically adjust their transmission rate. In this paper, we introduce a cross-layer framework for WCDMA based networks which aims to make the packet scheduling procedure more efficient. In addition to that, we further propose a traffic scheduling scheme which serves the connections not only according to their delay sensitivity, but also according to the predicted state of their wireless channel. The efficiency of the proposed scheme, in terms of average packet delay and channel utilization is verified via simulations.     

Boosting the feasibility pump

The feasibility pump (FP) has proved to be an effective method for finding feasible solutions to mixed integer programming problems. FP iterates between a rounding procedure and a projection procedure, which together provide a sequence of points alternating between LP feasible but fractional solutions, and integer but LP infeasible solutions. The process attempts to minimize the distance between consecutive iterates, producing an integer feasible solution when closing the distance between them. We investigate the benefits of enhancing the rounding procedure with a clever integer line search that efficiently explores a large set of integer points. An extensive computational study on benchmark instances demonstrates the efficacy of the proposed approach.