An empirical analysis of spreadsheet calculation

Spreadsheet calculation is a powerful tool in simple administrative data processing. Formulae in spreadsheets have similar forms to expressions in traditional programming languages, but the implementation of control structures is totally different. This paper contains an analysis of 101 spreadsheets made and used in business and government. The analysis concerns general properties, such as cell contents and referencing, the role of input, output and computation, and the different ways iteration is implemented. Finally some effects of expertise are studied. The results show that less than half of the available functions are really used, only one cell in 25 contains computation, and iteration is implemented in at least four different ways. Formulae are found to differ in their contents from expressions of programming languages, as control structures are implemented differently in these systems. Summation with a constant skip is suggested to be included in the set of functions of spreadsheet calculation.     

Data-driven and tool-supported elicitation of quality requirements in agile companies

Software Quality Journal - Quality requirements (QRs) are a key artifact needed to ensure the quality and success of a software system. Despite their importance, QRs rarely get the same degree of...     

Antioxidative properties and enzymatic synthesis of ascorbyl FA esters

Efficient synthesis of unsaturated FA esters of ascorbic acid is possible with only a small excess of one of the reactants in t-amyl alcohol using Candida antarctica lipase as biocatalyst. Using free acids, we obtained yields that were comparable to yields reached using vinyl-activated acyl donors (71, 80, and 86% yields of esters with FA excesses of 1∶1, 1∶1.5, and 1∶2, respectively). As very low water activity is needed to achieve sufficiently high yields of product, molecular sieves were used to improve the ascorbyl ester yields. Ascorbyl oleate is more amorphous and has a much lower m.p. and lower enthalpy of fusion than ascorbyl palmitate. This leads to a higher solubility of ascorbyl oleate in oil, resulting in an increased antioxidant effect compared to that of the palmitate. In an accelerated storage test using deodorized rapeseed oil, samples incubated with ascorbyl palmitate showed noticeable oxidation after 1 wk of storage, whereas samples incubated with ascorbyl oleate displayed negligible oxidation for 9 and 4 wk at 30 and 40°C, respectively.     

Li2MoO4‐based composite ceramics fabricated from temperature‐ and atmosphere‐sensitive MnZn ferrite at room temperature

The first magnetic ceramic composites manufactured, using the room‐temperature densification method are reported. The samples were prepared at room temperature using Li₂MoO₄ as a matrix and MnZn ferrite with loading levels of 10‐30 vol‐% followed by postprocessing at 120°C. The method utilizes the water solubility of the dielectric Li₂MoO₄ and compression pressure instead of high temperatures typical of conventional solid‐state sintering. Hence, composite manufacturing using temperature‐ and atmosphere‐sensitive materials is possible without special conditions. This was demonstrated with MnZn ferrite, which is prone to oxidation when heat treated in air. Samples manufactured with room‐temperature densification showed no signs of reactivity during processing, whereas reference samples sintered at 685°C suffered from oxidation and formation of an additional reaction phase. The densities achieved with different loading levels of MnZn ferrite with both methods were very similar. Measurements up to 1 GHz showed relatively high values of relative permittivity (21.7 at 1 GHz) and permeability (2.6 at 1 GHz) with 30 vol‐% loading of MnZn ferrite in the samples manufactured by room‐temperature densification. In addition, pre‐granulation is proposed to improve the processability of the composite powders in room‐temperature densification.     

Model microemulsions containing vegetable oils 2. Ionic surfactant systems

The phase behavior and the structure of ionic microemulsions, stabilized by sodium oleate and different alcohol cosurfactants, containing fatty acid esters or triglycerides as lipophilic components, have been investigated. Microemulsions containing triglycerides display a smaller stability region than microemulsions containing hydrocarbons or fatty acid esters. From structural investigations, using the NMR FT pulsed gradient spin echo method for measuring self-diffusion coefficients, differences in the microstructure are revealed as well. Adding an ester (or a hydrocarbon) to a microemulsion containing sodium oleate/pentanol will at certain compositions lead to a gradual transition from a bicontinuous to an oilcontinuous system, while this behavior cannot be detected when adding a triglyceride. Instead, a phase-separation occurs, and it is suggested that the larger molecular size of the triglyceride is responsible for the difference.     

Bio‐hybrid nanocomposite coatings from sonicated chitosan and nanoclay

Nanocomposite films and coatings with improved properties were produced from ultrasonic dispersed chitosan and hydrophilic bentonite nanoclay. Bio‐hybrid coatings were applied onto argon–plasma‐activated LDPE coated paper. The intercalation of chitosan in the silicate layers was confirmed by the decrease of diffraction angles as the chitosan/nanoclay ratio increased. Nanocomposite films and multilayer coatings had improved barrier properties against oxygen, water vapor, grease, and UV‐light transmission. Oxygen transmission was significantly reduced under all humidity conditions. In dry conditions, over 99% reduction and at 80% relative humidity almost 75% reduction in oxygen transmission rates was obtained. Hydrophilic chitosan was lacking the capability of preventing water vapor transmission, thus total barrier effect of nanoclay containing films was not more than 15% as compared with pure chitosan. Because to very thin coatings (≤1 μm), nanoclay containing chitosan did not have antimicrobial activity against test strains. All coating raw materials were “generally recognized as safe” (GRAS) and the calculated total migration was in all cases ≤6 mg/dm², thus the coatings met the requirements set by the packaging legislation. Processing of the developed bio‐hybrid nanocomposite coated materials was safe as the amounts of released particles under rubbing conditions were comparable with the particle concentrations in a normal office environment. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Fabrication and properties of composites from BST and polypropylene-graft-poly(styrene-stat-divinylbenzene)

In this work, ceramic–polymer composites were fabricated from barium strontium titanate powder (BST) and polypropylene-graft-poly(styrene-stat-divinylbenzene) (ER) using a twin-screw extruder. The compounding process was characterized by rheological measurements. The effects of volume loading of BST on dielectric and mechanical properties were investigated. The dielectric properties were measured as a function of frequency and BST loading. For example, the relative permittivity and loss tangent (tan δ) of the BST–ER composites at 1 GHz were gradually increased from 2.4 and 0.0001 to 28.5 and 0.0085, respectively, as the loading was increased from 0 to 50.5 vol.%. Stearic acid (StA) was used as a surface-modifier of the BST. With an approximate surface coverage of 83%, an improvement in processability and a slight increase of the permittivity was observed, while tan δ remained low. The excellent dielectric characteristics of these composites, with high permittivity and low tan δ, make them attractive novel electronic materials for high frequency applications.     

Electrical Resistance Tomography imaging of concrete

We apply Electrical Resistance Tomography (ERT) for three dimensional imaging of concrete. In ERT, alternating currents are injected into the target using an array of electrodes attached to the target surface, and the resulting voltages are measured using the same electrodes. These boundary measurements are used for reconstructing the internal (3D) conductivity distribution of the target. In reinforced concrete, the metallic phases (reinforcing bars and fibers), cracks and air voids, moisture gradients, and the chloride distribution in the matrix carry contrast with respect to conductivity. While electrical measurements have been widely used to characterize the properties of concrete, only preliminary results of applying ERT to concrete imaging have been published so far. The aim of this paper is to carry out a feasibility evaluation with specifically cast samples. The results indicate that ERT may be a feasible modality for non-destructive evaluation of concrete.     

Moderate anisotropy in the electrical conductivity of bulk MWCNT/epoxy composites

Bulk aligned multi-walled carbon nanotube films and their epoxy composites were prepared and their DC and AC conductivity studied. Nanotube films of up to 2 mm thickness were grown by catalytic chemical vapor deposition. Composites of nanotubes were made by infiltrating the films with a commercial epoxy. DC electrical resistivities in the axial direction of as-grown and purified films were found to be ∼1.2 Ωmm and ∼3.4 Ωmm, respectively. For the transverse direction the resistivity values were higher only with a factor of ∼2. In the case of composites, anisotropy is more pronounced showing more than an order of magnitude higher resistivity in the transverse direction (∼71.4 Ωmm) as compared to the axial value (∼4.2 Ωmm). AC behavior of the films investigated between 1 MHz and 3 GHz shows the presence of inductive and capacitive components at frequencies above ∼100 MHz. The moderate anisotropy for both DC and AC electrical properties are explained on the basis of the films’ structure combined with percolation theory and equivalent circuit models.