An algorithmic framework for convex mixed integer nonlinear programs

This paper is motivated by the fact that mixed integer nonlinear programming is an important and difficult area for which there is a need for developing new methods and software for solving large-scale problems. Moreover, both fundamental building blocks, namely mixed integer linear programming and nonlinear programming, have seen considerable and steady progress in recent years. Wishing to exploit expertise in these areas as well as on previous work in mixed integer nonlinear programming, this work represents the first step in an ongoing and ambitious project within an open-source environment. COIN-OR is our chosen environment for the development of the optimization software. A class of hybrid algorithms, of which branch-and-bound and polyhedral outer approximation are the two extreme cases, are proposed and implemented. Computational results that demonstrate the effectiveness of this framework are reported. Both the library of mixed integer nonlinear problems that exhibit convex continuous relaxations, on which the experiments are carried out, and a version of the software used are publicly available.     

Microdeformation behavior in nanotemplated epoxy thermosets: A study with in situ tensile deformation technique in transmission electron microscopy

Microdeformation behavior in nanostructured block copolymer‐toughened epoxy resins, or templated epoxy thermosets, was studied using an in situ tensile deformation technique performed directly in a transmission electron microscope. The observed microdeformation modes were found to correlate well with the macroscopic mechanical properties of the materials. In the order of decreasing macroscopic fracture toughness, the microdeformation modes were observed to change from large uniform plastic deformation over an extensive area, to localized plastic deformation bands, to little plastic deformation observed in the most brittle material. A similar trend was also observed when samples of the same material were tested at different temperatures, reflecting changes in the deformation mechanism as a function of temperature. Structural defects were observed in nanotoughening phases when plastic deformation was observed. The implication of the observed microdeformation modes to the macroscopic toughening mechanisms is discussed in the context of the micromorphology of the nanometer sized toughening phases and parameters of the epoxy matrix chemistry such as bromination, molecular weight, and interfacial miscibility. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 393–406, 2009     

Phthalocyanines bearing bulky cycloalkylmethyl substituents on non-peripheral sites

Octasubstituted phthalocyanines bearing bulky (cyclopentyl)methyl- and (cyclohexyl)methyl-substituents in non-peripheral positions are prepared and characterised. The synthesis of the precursor phthalonitriles is achieved through nickel-catalysed cross-coupling employing alkylzinc reagents. In the case of the (cyclopentyl)methyl derivative the formal precursor is 5-hexenyl bromide which yields the cyclised material exclusively on formation of the zinc reagent and subsequent cross-coupling.     

Particle size control and dependence on solution pH of carboxylate–alumoxane nanoparticles

A series of water dispersible carboxylate–alumoxane nanoparticles were prepared by the reaction of various carboxylic acids with the mineral boehmite. The acids used were: acetic (A–H), methoxyacetic (MA–H), methoxyethoxyacetic (MEA–H), methoxyethoxyethoxyacetic (MEEA–H), and lysine (L–H). For each of the derived carboxylate–alumoxanes, particle size measurements were obtained by means of photon correlation spectroscopy (PCS) as a function of solution pH. In all cases, at higher pHs, slight increases in solution basicity corresponded to large increases in particle size. At lower pHs, however, changes in solution basicity yielded only slight to moderate increases in particle size. It was also found during these investigations that methoxyacetic–alumoxane (MA–A) had a large buffering capacity, and that this effect could be explained by correlation with the aluminum:carboxylate group ratio for the various carboxylate–alumoxanes.     

Temperature-programmed synthesis of micron-sized multi-responsive microgels

A new synthetic protocol for the synthesis of large diameter (2.5 to 5 μm), temperature-, and pH-responsive microgels via aqueous surfactant-free radical precipitation copolymerization is presented. We have found that in this size range, which is not typically attainable using traditional dispersion polymerization approaches, excellent monodispersity and size control are achieved when the synthesis employs a programmed temperature ramp from 45 to 65 °C during the nucleation stage of the polymerization. A combined kinetic and thermodynamic hypothesis for large particle formation under these conditions is described. Particle sizes, volume phase transition temperatures, and pH responsivity were characterized by particle tracking and photon correlation spectroscopy to illustrate their similar behavior to particles made via more traditional routes. These particles have been enabling for various studies in our group where microscopic visualization of the particles is required.     

Thermally degradable maleimides for reworkable adhesives

New thermosetting materials were developed for reworkable adhesive applications by introducing acetal ester groups as thermally degradable linkages into maleimide compounds. The synthesis of compounds containing maleimide functionality and acetal ester linkages was conducted by a one‐step neat reaction from commercially available materials. The polymerization process and thermal degradation of the synthesized materials were studied. It was found that the acetal ester linkage degraded rapidly above 225 °C, and introduction of this linkage into the adhesive formulation led to improved reworkability of adhesively bonded substrates. A mechanism for reworkability was proposed based on the insight provided by experimental and modeling work. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1073–1084, 2009     

Tariff concessions in production sourcing

In this paper, we study a multi-stage production sourcing problem where tariff concessions can be exploited at the firm level using free trade agreements between countries. To solve the problem, an algorithm which embeds a very large-scale neighborhood (VSLN) search into a simulated annealing framework is developed. A numerical study is conducted to verify the effectiveness of the solution approach.     

Large‐scale eigenvalue calculations for stability analysis of steady flows on massively parallel computers

This paper presents an approach for determining the linear stability of steady states of partial differential equations (PDEs) on massively parallel computers. Linearizing the transient behavior around a steady state solution leads to an eigenvalue problem. The eigenvalues with the largest real part are calculated using Arnoldi's iteration driven by a novel implementation of the Cayley transformation. The Cayley transformation requires the solution of a linear system at each Arnoldi iteration. This is done iteratively so that the algorithm scales with problem size. A representative model problem of three‐dimensional incompressible flow and heat transfer in a rotating disk reactor is used to analyze the effect of algorithmic parameters on the performance of the eigenvalue algorithm. Successful calculations of leading eigenvalues for matrix systems of order up to 4 million were performed, identifying the critical Grashof number for a Hopf bifurcation. Copyright © 2001 John Wiley & Sons, Ltd.     

μ‐Oxo‐bis[(η5‐1,2‐dicarbaundecabor­ato)bis(N,N‐dimethylacetamidinato)tantalum] dichloromethane hemisolvate

The structure of the title compound, [Ta₂O(C₂B₉H₁₁)₂(C₄H₉­N₂)₄]·0.5CH₂Cl₂, contains two (C₂B₉H₁₁)Ta[NC(Me)NMe₂]₂ units bridged by a nearly linear [Ta—O—Ta 163.4 (4)°] μ‐oxo ligand. The dichloromethane molecule lies on a twofold axis.