Optimization problems involving the first Dirichlet eigenvalue and the torsional rigidity

We present some open problems and obtain some partial results for spectral optimization problems involving measure, torsional rigidity and first Dirichlet eigenvalue.Comment: 18 pages, 4 figure

Does work experience help to become a medical specialist?

medical care;universities;job search;education;duration analysis

Warehouse design and planning: A mathematical programming approach

The dynamic nature of today's competitive markets compels organizations to an incessant reassessment in an effort to respond to continuous challenges. Therefore, warehouses as an important link in most supply chains, must be continually re-evaluated to ensure that they are consistent with both market's demands and management's strategies. A number of warehouse decision support models have been proposed in the literature but considerable difficulties in applying these models still remain, due to the large amount of information to be processed and to the large number of possible alternatives. In this paper we discuss a mathematical programming model aiming to support some warehouse management and inventory decisions. In particular a large mixed-integer nonlinear programming model (MINLP) is presented to capture the trade-offs among the different inventory and warehouse costs in order to achieve global optimal design satisfying throughput requirements.(undefined)info:eu-repo/semantics/publishedVersio

Web Crippling of Stainless Steel Cold-formed Beams

The results of an investigation on the web crippling strength of cold-formed stainless steel channel sections are presented in this paper. The steels under consideration are AlSI Type 430 stainless steel and a modified AlSI Type 409, designated Type 3CR12 corrosion resisting steel. The lipped channel sections were manufactured by a press braking process. Beams were tested in pairs, lips facing, in an interior-one-flange loading configuration. Experimental results were compared with the theoretical predictions given in the 1991 edition of the Specification for the Design of Cold-Formed Stainless Steel Structural Members. It was concluded in this study that the experimental results compare reasonably well with the theoretical predictions. For longer bearing lengths the theoretical strengths appear to be conservative

Distortional Buckling of Cold-formed Stainless Steel Compression Members

In this paper the critical local buckling strength of cold-formed stainless steel compression members, with special emphasis on the method developed by Lau and Hancock for distortional buckling is discussed. Cold-formed stainless steel channel and I-section members under axial compression in distortional buckling are analysed. A control experiment is carried out for comparing analytical methods with a finite element method and experimental values

Dispersion and polarization conversion of whispering gallery modes in arbitrary cross-section nanowires

We investigate theoretically the optical properties of Nano-Wires (NWs) with cross sections having either discrete or cylindrical symmetry. The material forming the wire is birefringent, showing a different dielectric response in the plane and along the axis of the wire, which is typically the case for wires made of wurtzite materials, such as ZnO or GaN. We look for solutions of Maxwell`s equations having the proper symmetry. The dispersions and the linewidths versus angle of incident light for the modes having high momentum in the cross-section plane, so called whispering gallery modes, are calculated. We put a special emphasis on the case of hexagonal cross sections. The energy positions of the modes for a set of azimuthal quantum numbers are shown. We demonstrate the dependence of the energy splitting between TE and TM modes versus birefringence. The polarization conversion from TE to TM with increase of the axial wave vectoris discussed for both cylindrical and discrete symmetry.Comment: 9 pages, 10 figure

Extending the functionalities of shear-driven chromatography nano-channels using high aspect ratio etching

An new injection system is presented for shear-driven chromatography. The device has been fabricated by high aspect ratio etching of silicon. The performance of the injection slit is studied through the aid of computational fluid dynamics, and the first experimental results are presented