Durability of a polymer with triple-shape properties

A series of cyclic thermo-mechanical measurements was conducted on segregated poly(ester urethane) to study substantial changes in triple-shape properties as a result of hydrolytic aging (80 °C). Prior to the analysis of aging effects, a concept of triple-shape testing was elaborated, starting with the implementation of two distinct programming units. The first one included a deformation at 60 °C to ?_m1 = 100% (temporary shape B) and its fixing through soft segment crystallization by cooling to −20 °C under constant strain. The second one consisted of a deformation at −20 °C to ?_m2 = 200% (temporary shape A) and its stabilization through soft segment vitrification as achieved by cooling to −60 °C under fixed strain constraint. Then, gradual heating of the polymer from below to above its thermal transition temperatures gave two independent shape recovery responses in the reverse order of shape fixing: A → B through passing the glass transition by heating from −60 to 23 °C and B → C (back to the permanent shape), when heating the material from 23 to 60 °C and thus above its soft segment melting temperature. In a progressive approach, the storage of loading history through the sequential fixing of two temporary shapes was proven by the development of shape recovery stresses under constrained environment. With the implementation of the two testing methods several aging-related effects could be detected. Good shape fixing abilities ≥90% for both shapes were found and contrasted by significant changes in shape recoverabilities and stress storage capacities. Further insights derived from differential scanning calorimetry (DSC) measurements, indicating an aging-related growth in soft segment crystallinity, and dynamic mechanical analysis (DMA), suggesting a plasticizer effect of water onto the polymer matrix and that aging favoured an increase in cross-linking density.     

Alignment of retention time obtained from multicapillary column gas chromatography used for VOC analysis with ion mobility spectrometry

Multicapillary column (MCC) ion mobility spectrometers (IMS) are increasingly in demand for medical diagnosis, biological applications and process control. In a MCC-IMS, volatile compounds are differentiated by specific retention time and ion mobility when rapid preseparation techniques are applied, e.g. for the analysis of complex and humid samples. Therefore, high accuracy in the determination of both parameters is required for reliable identification of the signals. The retention time in the MCC is the subject of the present investigation because, for such columns, small deviations in temperature and flow velocity may cause significant changes in retention time. Therefore, a universal correction procedure would be a helpful tool to increase the accuracy of the data obtained from a gas-chromatographic preseparation. Although the effect of the carrier gas flow velocity and temperature on retention time is not linear, it could be demonstrated that a linear alignment can compensate for the changes in retention time due to common minor deviations of both the carrier gas flow velocity and the column temperature around the MCC-IMS standard operation conditions. Therefore, an effective linear alignment procedure for the correction of those deviations has been developed from the analyses of defined gas mixtures under various experimental conditions. This procedure was then applied to data sets generated from real breath analyses obtained in clinical studies using different instruments at different measuring sites for validation. The variation in the retention time of known signals, especially for compounds with higher retention times, was significantly improved. The alignment of the retention time—an indispensable procedure to achieve a more precise identification of analytes—using the proposed method reduces the random error caused by small accidental deviations in column temperature and flow velocity significantly.     

The carbon versus mass diagram to visualize and exploit FTICR‐MS data of natural organic matter

A two‐dimensional diagram is proposed, in which the carbon number of each formula is plotted against its nominal mass, to visualize large sets of molecular formula data that can be derived from data generated by ultrahigh‐resolution Fourier transform ion cyclotron resonance‐MS. In such a carbon versus mass (CvM) diagram, each formula (C_cH_hO_o) is unambiguously described by c, its (nominal) mass and the parameter i = c + o. Calculations of chemically allowable formulas illustrate that organic molecules occupy only certain spaces in such a diagram. The extension of these spaces increases with molecular mass in x‐direction (hydrogenation) and y‐direction (oxygenation). The data sets of molecules determined in natural organic matter(NOM) occupy only a certain range of the allowable space. The intensity of the mass spectrometric signals can be included as the third dimension into a CvM diagram. Separate CvM diagrams can be plotted for NOM molecules that include different heteroatoms. The benefits of the CvM diagram are illustrated by application onto data sets of fulvic acids from riverine and marine origin, of secondary organic aerosol, including organosulfates and organonitrates, as well as of ozonation of fulvic acids. The CvM diagram is a useful tool to visualize the elemental regularities in NOM isolates as well as the differences between isolates. It may also be applicable to large sets of molecular formula data generated in other disciplines such as petroleum biogeochemistry or metabolomics. Copyright © 2010 John Wiley & Sons, Ltd.     

Methyl β‐d‐fructopyranoside

In methyl β‐d ‐fructopyranoside, C₇H₁₄O₆, the thermodynamically most stable methyl glycoside of the ketose d ‐fructose, the pyranose ring is close to being an ideal ²C₅ chair. The compound forms bilayers involving a complex hydrogen‐bonding pattern of five independent hydrogen bonds. Graph‐set analysis was applied to distinguish the hydrogen‐bond patterns at unary and higher level graph sets.     

19.4%‐efficient large‐area fully screen‐printed silicon solar cells

We demonstrate industrially feasible large‐area solar cells with passivated homogeneous emitter and rear achieving energy conversion efficiencies of up to 19.4% on 125 × 125 mm² p‐type 2–3 Ω cm boron‐doped Czochralski silicon wafers. Front and rear metal contacts are fabricated by screen‐printing of silver and aluminum paste and firing in a conventional belt furnace. We implement two different dielectric rear surface passivation stacks: (i) a thermally grown silicon dioxide/silicon nitride stack and (ii) an atomic‐layer‐deposited aluminum oxide/silicon nitride stack. The dielectrics at the rear result in a decreased surface recombination velocity of S_rear = 70 cm/s and 80 cm/s, and an increased internal IR reflectance of up to 91% corresponding to an improved J_sc of up to 38.9 mA/cm² and V_oc of up to 664 mV. We observe an increase in cell efficiency of 0.8% absolute for the cells compared to 18.6% efficient reference solar cells featuring a full‐area aluminum back surface field. To our knowledge, the energy conversion efficiency of 19.4% is the best value reported so far for large area screen‐printed solar cells. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Numerical Simulation of a Turbulent FSI Benchmark Case

In an effort to expand the capabilities of a validated simulation environment for fluid-structure interaction to turbulent flows, we present the simulation of a turbulent FSI benchmark case with large displacements in a simplified two-dimensional unsteady RANS setup. We find a fair agreement to experimental data that encourages further refinement of our approach and future three-dimensional simulations with eddy-resolving schemes. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Efficient Observer Design for Multirate Sampled-Data Systems

This contribution deals with the observer design for linear multirate sampled systems. The proposed algorithm is fea-tured by a time-invariant modelling approach. It is shown that a multirate state observer can be derived by gradually building up the observer gain matrix by means of optimization based design methods in combination with a pole placement observer design. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)