A comparison of two analytical evaluation methods for educational computer games for young children

In this paper we describe a comparison of two analytical methods for educational computer games for young children. The methods compared in the study are the Structured Expert Evaluation Method (SEEM) and the Combined Heuristic Evaluation (HE) (based on a combination of Nielsen’s HE and the fun-related concepts from Malone and Lepper) with both usability and fun heuristics for children’s computer games. To verify SEEM’s relative quality, a study was set up in which adult evaluators predicted problems in computer games. Outcomes based on thoroughness (whether the analytical method finds all problems), validity (whether the analytical method uncovers problems that are likely to be true) and appropriateness (whether the method is applied correctly) are compared. The results show that both the thoroughness and validity of SEEM are higher than the thoroughness and validity of the Combined HE. The appropriateness scores indicate that SEEM gives evaluators more guidance when predicting problems than the Combined HE does.

Algorithms for testing fault-tolerance of sequenced jobs

We study the problem of testing whether a given set of sequenced jobs can tolerate transient faults. We present efficient algorithms for this problem in several fault models. A fault model describes what types of faults are allowed and specifies assumptions on their frequency. Two types of faults are considered: hidden faults, that can only be detected after a job completes, and exposed faults, that can be detected immediately. First, we give an O(n)-time fault-tolerance testing algorithm, for both exposed and hidden faults, if the number of faults does not exceed a given parameter k.     

Selective cysteine <- serine replacements in p-hydroxybenzoate hydroxylase from Pseudomonas fluorescens allow the unambiguous assignment of Cys211 as the site of modification by spin-labeled p-chloromercuribenzoate

p-Hydroxybenzoate hydroxylase from Pseudomonas fluorescens containsfive sulfhydryl groups per subunit. Cysteine serine replacementsshow that the thiols are not essential for catalysis. The increaseddissociation constant for FAD in mutant Cysl58Ser suggests thatCysl58 is important for the solvation of the pyrophosphate moietyof the prosthetic group. Wild-type p-hydroxybenzoate hydroxylaseis rapidly inactivated by mercurial compounds. Inactivationby a spin-labeled derivative of p-chloromercuribenzoate is fullyabolished in mutant Cys211Ser. Incorporation of the spin labelin the other Cys Ser mutants strongly impairs substrate bindingwithout affecting the catalytic properties of the FAD. The resultsare discussed with respect to previous tentative assignmentsfrom chemical modification studies and in light of the 3-D structureof the enzyme-substrate complex.     

Predicting effectiveness of children participants in user testing based on personality characteristics

This paper describes an experiment to determine which personality characteristics can be used to predict whether a child will make an effective participant in a user test, both in terms of the number of identified problems and the percentage of verbalised problems. Participant selection based on this knowledge can make user testing with young children more effective. The study shows that the personality characteristic Curiosity influences the number of identified problems; a combination of the personality characteristics Friendliness and Extraversion influences the percentage of verbalised problems. Furthermore, the study shows that selection of children based on these criteria does not lead to finding an unrepresentative sample of the product's problems.     

Electrodialytic removal of cadmium from wastewater sludge

This paper presents for the first time laboratory results demonstrating electrodialytic removal of Cd from wastewater sludge, which is a method originally developed for soil remediation. During the remediation a stirred suspension of wastewater sludge was exposed to an electric dc field. The liquid/solid (ml/g fresh sludge) ratio was between 1.4 and 2. Three experiments were performed where the sludge was suspended in distilled water, citric acid or HNO3. The experimental conditions were otherwise identical. The Cd removal in the three experiments was 69, 70 and 67%, respectively, thus the removal was approximately the same. Chemical extraction experiments with acidic solutions showed that 5-10 times more Cd could be extracted from decomposed sludge than from fresh sludge. It is likely that the mobilization of Cd during decomposition of the sludge contributes to the efficient removal of Cd by the electrodialytic method. Extraction experiments and electrodialytic remediation using distilled water as enhancement agent showed that 0.3% Cd could be extracted from decomposed sludge during 1 week in closed flasks, whereas 69% was removed during 2 weeks of electrodialytic remediation in a stirred solution in contact with atmospheric air. A combination of aerobic decomposition and electrodialytic treatment could be a promising method for Cd removal from wastewater sludge, and thus Cd could be removed without the addition of chemicals to the sludge.     

Mixed Power Control with Directed Assignment (MPCDA), a Method for Interference Reduction in Channelized Wireless Systems

Power control, often coupled with dynamic channel assignment, has been viewed as a promising answer to the challenge of reducing interference and increasing capacity. Indiscriminate use of power control, however, may exacerbate the near-far-end problem on the down link, and give rise to other complications when users are mobile. We propose a power control policy that can alleviate the near-far-end interference caused by the use of either the same channel or neighbor channels inside the same cell, while at the same time aiding in the reduction of interference from different cells through user matching. We present a heuristic algorithm for user matching, which is distributed and simple to implement. The method can be combined with an array of either fixed or dynamic channel assignment algorithms and applies to both circuit-based and packet-based traffic. It is ideal for fixed or slow circuit-based traffic and for packet-based traffic.A duality relationship is derived for the proposed power control policy between the signal-to-interference ratio of two interfering users experienced in the two communication directions. This relationship enables one to validate channel assignment decisions on both communication directions by analyzing only the decisions for one.     

Determination of the fibre orientation distribution of a mineral wool network and prediction of its transverse stiffness using X-ray tomography

A method to determine the orientation and diameter distributions of mineral wool fibre networks using X-ray tomography and image analysis is presented. The method is applied to two different types of mineral wool: glass wool and stone wool. The orientation information is obtained from the computation of the structure tensor, and the diameter is estimated by applying a greyscale granulometry. The results of the image analysis indicate the two types of fibres are distributed in a 2D planar arrangement with the glass wool fibres showing a higher degree of planarity than the stone wool fibres. The orientation information is included in an analytical model based on a Euler–Bernoulli beam approximation. The model enables prediction of the transverse stiffness. It is indicated that the glass wool transverse stiffness is lower than the stone wool transverse stiffness. Comparison with experimental results confirms the assumption that the underlying deformation mechanism of mineral wool is the bending of fibre segments between bonds.