Spatial No-Waiting Stations with Moving Customers

We analyze spatial MAP/G/∞-, spatial MAP/G/c/0¹ and spatial Cox/G/∞-stations with group arrivals over some Polish space X (with Borel σ-algebra X), including the aspect of customer motion in space. For models with MAP-input, characteristic differential equations are set up that describe the dynamics of phase dependent random functions Q _r;ij (u,t;S′), where Q _r;ij (u,t;S′) is the probability to observe, at time u≤t, the number r of those customers in some source set S′∈X, who will be in a destination set S∈X at time t. For Cox/G/∞-stations, i.e., infinite server stations with doubly stochastic input, the arrival intensities as well as service times may depend on some general stochastic process (J′ _t ) _t≥0 with countable state space. For that case we obtain explicit expressions for space–time distributions as well as stationary and non-stationary characteristics.     

Photochemistry of refractive index structures in poly(methyl methacrylate) by femtosecond laser irradiation

Femtosecond, subablation threshold photomodification of poly(methyl methacrylate) (PMMA) at 387 nm is explored to enable fabrication of optical components. Volatile fragment analysis (thermal desorption gas chromatography-mass spectrometry) and molecular weight distribution monitoring (size exclusion chromatography) suggest photochemical modification, involving direct cleavage of the polymer backbone and propagation via chain unzipping under formation of monomers, similar to the pyrolytic degradation of PMMA. Waveguides were produced in undoped, clinical-grade PMMA, showing an increased refractive index in the laser focal region (Dnmax=4x10(-3)).     

Adaptive unstructured finite element method for two-dimensional detonation simulations

A non-equilibrium reacting flow methodology has been added to a conservative, monotonic, compressible flow solver to allow numerical simulations of gas detonations. This flow solver incorporates unstructured dynamically adaptive meshes with the Finite Element Method – Flux Corrected Transport (FEM-FCT) scheme, which has shown excellent predictive capability of various non-reacting compressible flows. A two-step induction parameter model was used to model the combustion of the gas phase coupled with an energy release equation which was simulated with a point implicit finite element scheme. This combustion model was then applied to a two-dimensional detonation test case of a hypothetical fuel:oxygen mixture. The detonation simulation yielded two transverse waves which continued to propagate. This feature and the detonation shock speed mean and fluctuations were found to be grid-independent based on a resolution of about twenty elements within the average induction length. The resolution was efficiently achieved with the unstructured dynamically adaptive finite elements, which were three orders of magnitude less in number then required for uniform discretization. Received 26 August 1996 / Accepted 31 March 1997     

Affinity chromatography of beta-galactosidase on controlled-pore glass derivatives.

Several controlled-pore glass (CPG) derivatives were examined as supports for the affinity chromatographic purification of the enzyme beta-galactosidase. The competitive inhibitor p-aminophenyl-beta-D-thiogalactopyranoside was coupled to an azelaic acid and a malonic acid derivative of 750-A alkylamine CPG of 80-120 mesh and to an azelaic acid derivative of 550-A alkylamine CPG of 40-80 mesh. The latter derivative exhibited particularly good load capacity and separation efficiency; however, both arm lengths were effective. Hydrophobic interactions between the arm and the enzyme contribute to the separation.