Mean‐risk optimization of electricity portfolios

We present a mathematical model with stochastic input data for mean‐risk optimization of electricity portfolios containing several physical components and energy derivative products. The model is designed for the optimization horizon of one year in hourly discretization. The aim consists in maximizing the mean book value of the portfolio at the end of the optimization horizon and, at the same time, in minimizing the risk of the portfolio decisions. The risk is measured by the conditional value‐at‐risk and by some multiperiod extension of CVaR, respectively.We present numerical results for a large‐scale realistic problem adapted to a municipal power utility and study the effects of varying weighting of risk. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Speciation of trace amounts of aluminium in percolating water of forest soil by online coupling HPLC-ICP-MS

Procedures were developed for the speciation of trace amounts of aluminium present in percolating water of forest soil by online coupling of different chromatographic separation methods to an ICP-MS detection system. Inorganic and organic aluminium species were fractionated on a cation exchange column IONPAC CG12 (10-32). Phytotoxic polymeric aluminium hydroxides, as e.g. Al₁₃ (AlO₄Al₁₂(OH)₂₄(H₂O)₁₂ ⁷⁺), were determined using pyrocatechol violet (PCV) as a species dependant complexing reagent prior to the cation exchange step. Size fractionation of the organic aluminium species was obtained by size exclusion chromatography using the columns Superdex-75-HR 10/30 and Superdex-Peptide-HR 10/30. Validation of the speciation procedures proved that online coupling HPLC to the element selective and sensitive ICP-MS detection system leads to low detection limits of 0.3–0.6 μg/L and high precision and reproducibility (1.2–3.5%) of the speciation procedures. Speciation data determined for aluminium in a percolating water of the Zierenberg catchment are given. Received: 20 November 1998 / Revised: 28 January 1999 / Accepted: 3 February 1999     

Spectroscopic imaging techniques for characterization of polymer morphologies: a combination of infrared and electron microscopy

The morphological characterization of polymer blends consisting of polyamide and poly(tetrafluoroethylene) using FT-IR spectroscopy and electron microscopy is described. To enhance the lateral resolution - one of the main limits in infrared spectroscopy - a combination with scanning electron microscopy and analytical electron microscopic methods of a transmission electron microscope was made. The possibilities of electron energy loss spectroscopy and energy filtered transmission electron microscopy (EFTEM) in the area of polymer characterization are outlined.     

The effect of specific nucleation on molecular and supermolecular orientation in isotactic polypropylene

The molecular and supermolecular orientation, morphology and structural changes observed during cold drawing of injection moulded isotactic polypropylene modified by specific α, and β nucleating agents were studied by polarised photoacoustic FTIR spectroscopy, wide-angle X-ray diffraction and differential scanning calorimetry. Significantly lower molecular orientation was found in the core of the β-nucleated injection moulded specimens as compared to unmodified and α-nucleated materials. This has been ascribed to the fast growth of the β-crystallites which inevitably dislocates the flow-induced orientation within the crystalline regions and in their vicinity. Moreover, it was found that the presence of the developed β-crystallites distinctly diminishes the efficiency of the orientational solid-state drawing assessed on both levels of the hierarchical structure (molecular and crystalline). This structural observation is directly connected with macroscopic softening effect of the β-phase: lowering the yield stress and flattening the neck shoulder. Thus, the interrelation between the microstructural and macroscopic effects of the β-phase could be described as a feedback process.     

Preparation and properties of thin films of hyperbranched polyesters with different end groups

Hyperbranched polyesters (HBP) with different end groups were prepared as thin films. They were characterized with regard to their chemical composition, thickness, optical constants and morphology using infrared spectroscopy, spectroscopic ellipsometry, and atomic force microscopy. The surface properties of the films were determined by zeta‐potential and contact angles measurements. The differences in the molecular structure and surface energetic and acid‐base properties between HBP materials with carboxylic, hydroxy and acetoxy end groups result in differences in their swelling behavior in atmospheric humidity. The swelling behavior at different atmospheric humidity was observed in situ using spectroscopic ellipsometry and reflectometric interference spectroscopy. From the results it can be concluded that HBP films can be used potentially as sensoric materials.     

Characterization of a poly(ethersulphone) by on-line coupling of size exclusion chromatography with NMR and FTIR spectroscopy

An on-line detection „on the flow”︁ during the size exclusion chromatography run using FTIR and NMR spectrometers was applied to investigate the liquid chromatographic separation process of oligomers and to identify the separated chromatographic compounds. The FTIR and NMR detectors give real-time information about the chemical structure and functional groups of the eluated species. The preferences and limits of the on-line coupling were discussed using an oligomeric hydroxyl terminated poly(ethersulphone) as an example. Molecular weights could be calculated from the ¹H-NMR spectra of the separated species using the intensities of end-group and main-chain signals. Residues of N-methylpyrrolidone which was used as solvent in the oligomer synthesis were identified by the FTIR detector.     

Hierarchy of Order in Liquid Crystalline Polycaps

When outfitted with long alkyl chains , polycaps, capsules along a polymer chain, spontaneously organize themselves into a two-dimensional liquid crystalline phase. Further organization results from shearing or pulling the liquid crystalline samples, producing three-dimensional assemblies of micrometer-wide, infinitely long fibers (see schematic representation).     

Thermal lens effects in an Er<Superscript>3+</Superscript>:YAG laser with crystalline fiber geometry

A resonantly diode-pumped high-power continuous-wave Er³⁺:YAG laser with a crystalline fiber geometry based on total-internal-reflection pump guiding is reported. Up to 9.4 W of output power could be generated and a slope efficiency of 46.8% was achieved. Intrinsic efficiencies reached up to 48.8% and an optimum outcoupling of ∼20% was found. A strong thermal lens was observed and cavity stability and hysteresis effects were studied.     

Using the solvation parameter model to characterize functionalized ionic liquids containing the tris(pentafluoroethyl)trifluorophosphate (FAP) anion

Ionic liquids (ILs) containing the tris(pentafluoroethyl)trifluorophosphate anion [FAP]⁻ have attracted increased attention due to their unique properties including ultrahigh hydrophobicity, hydrolytic stability, and wide electrochemical window. In this study, the solvation parameter model is used via gas chromatography to characterize the solvation interactions of seven ILs containing amino, ester, and hydroxyl functional groups appended to the cation and paired with [FAP]⁻, as well as three ILs containing the bis[(trifluoromethyl)sulfonyl]imide anion [NTf₂]⁻. The role of the functional groups, nature of the counter anion, and cation type on the system constants were evaluated. ILs containing [FAP]⁻ possessed lower hydrogen bond basicity than NTf₂-based ILs having the same cationic component; in the case of hydroxyl-functionalized cations, the presence of [FAP]⁻ led to an enhancement of the hydrogen bond acidity, relative to the NTf₂-analogs. The system constants support the argument that [FAP]⁻ weakly coordinates the cation and any appended functional groups, promoting properties of the cation which might be masked by stronger interactions with other anion systems. The chromatographic performance of the IL stationary phases was evaluated by examining the retention behavior and separation selectivity for chosen analytes. The results from this work can be used as a guide for choosing FAP-based ILs capable of exhibiting desired solvation properties while retaining important physical properties including high thermal stability and high hydrophobicity. Figure In this study, the solvation parameter model is used via gas chromatography to characterize the solvation interactions of seven ILs containing amino, ester, and hydroxyl functional groups appended to the cation and paired with tris(pentafluoroethyl)trifluorophosphate [FAP]⁻, as well as three ILs containing the bis[(trifluoromethyl)sulfonyl]imide anion [NTf₂]⁻. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.