Combined erosion and corrosion of thermal sprayed WC and CrC coatings

This paper presents investigations of the combined effect of erosion and corrosion on one stainless steel and four different thermal sprayed coatings with carbide particles in a metal matrix. The materials were exposed to flowing synthetic sea water containing sand. Pure erosion, electrochemical corrosion and total material loss were determined at different sand concentrations. The effect of exposure time was also studied. The results show that erosion is the dominating process at high sand concentrations while corrosion is important at lower concentrations. The relative importance depends on the material. The corrosion resistance of the metal matrix has great influence on the total material loss rate. For the coating with lowest corrosion resistance there seems to be a synergistic effect between the mechanical and electrochemical processes.     

Test generation through logic programming

Utilization of the logic programming language Prolog in solving CAD/CAM/CAT problems is discussed. It is demonstrated through examples that, with Prolog, solutions are obtained through proper problem definition rather than by algorithmic procedures.The examples offered are in the area of test generation for digital circuits. A very simple formulation of the D-algorithm is presented, and it is demonstrated that levelling of the circuit is not necessary.Finally, we suggest other areas of CAD/CAM/CAT that may take advantage of logic programming.     

Food poisoning potential of Bacillus cereus strains from Norwegian dairies

Characteristics concerning diarrhoeal potential were investigated in B. cereus dairy strains. The thirty-nine strains, isolated from whipping cream, were tested for cytotoxicity after culturing at human body temperature as well as 25 degrees C and 32 degrees C. At 37 degrees C, none of the strains were highly cytotoxic. This observation suggests that those strains should be considered to pose a minor risk with regard to diarrhoeal food poisoning. However, some strains were moderately or highly cytotoxic when grown at 25 degrees C and 32 degrees C. While the majority of the strains were able to grow at refrigeration temperatures, only four B. weihenstephanensis strains were identified among them when subjected to discriminative PCR assays and growth temperatures which delimit this species.     

A feature selection method for multilevel mental fatigue EEG classification

Two feature selection approaches for multilevel mental fatigue electroencephalogram (EEG) classification are presented in this paper, in which random forest (RF) is combined with the heuristic initial feature ranking scheme (INIT) or with the recursive feature elimination scheme (RFE). In a "leave-one-proband-out" evaluation strategy, both feature selection approaches are evaluated on the recorded mental fatigue EEG time series data from 12 subjects (each for a 25-h duration) after initial feature extractions. The latter of the two approaches performs better both in classification performance and more importantly in feature reduction. RF with RFE achieved its lowest test error rate of 12.3% using 24 top-ranked features, whereas RF with INIT reached its lowest test error rate of 15.1% using 64 top-ranked features, compared to a test error rate of 22.1% using all 304 features. The results also show that 17 key features (out of 24 top-ranked features) are consistent between the subjects using RF with RFE, which is superior to the set of 64 features as determined by RF with INIT.     

Load case reduction for offshore wind turbine support structure fatigue assessment by importance sampling with two‐stage filtering

A complete fatigue assessment for operational conditions for offshore wind turbines involves simulating thousands of environmental states. For applications such as optimization, where this assessment needs to be repeated many times, that presents a significant computational problem. Here, we propose a novel way of reducing the number of simulated environmental states (load cases) while maintaining an acceptable accuracy. From one full fatigue analysis of a base design, the OC3 monopile (with the NREL 5MW turbine), the distribution of fatigue damage per load case can be used to estimate the lifetime fatigue damage of a range of modified designs. Using importance sampling and a specially adapted two‐stage filtering procedure, we obtain pseudo‐optimal sets of load cases from which the fatigue damage is estimated. This is applied to seven different designs that have been modified to emulate iterations of an optimization loop. For several of these designs, sampling less than 1% of all load cases can give damage estimates with median errors of less than 2%. Even for the most severe cases, using 3% of the environmental states yields a maximum error of 10%. While further refinement is possible, the method is considered viable for applications within design optimization and preliminary design.     

Scan Test Response Compaction Combined with Diagnosis Capabilities

As today’s process technologies are combined with ever increasing design sizes, the result is a dramatic increase in the number of scan test vectors that must be applied during manufacturing test. The increased chip complexities, in combination with the smaller feature sizes, require that we now address defect mechanisms that safely could be more or less ignored in earlier technologies. Scan based delay fault testing (AC-scan) enhances defect coverage as it addresses the dynamic behavior of the circuit under test. Unfortunately, the growing number of scan test vectors may in turn result in costly tester reloads and unacceptable test application times. In this paper, we devise a new scan test response compaction scheme based on finite memory compaction (a class of compactors originally proposed in Rajski et al., Convolutional compaction of test responses, 2003). Our scheme is diagnosis friendly, which is important when it comes to maintain throughput on the test floor (Leininger et al., Compression mode diagnosis enables high volume monitoring diagnosis flow, 2005; Stanojevic et al., Enabling yield analysis with X-compact, 2005). Yet, the compactor has comparable performance to other schemes (Mitra et al., X-compact: an efficient response compaction technique, 2004; Mitra S et al., X-tolerant test response compaction, 2005; Rajski et al., Convolutional compaction of test responses, 2003) when it comes to ‘X’ tolerance and aliasing.     

Short communication: Discrimination between retail bovine milks with different fat contents using chemometrics and fatty acid profiling

We used a multivariate chemometric approach to differentiate or associate retail bovine milks with different fat contents and non-dairy beverages, using fatty acid profiles and statistical analysis. We collected samples of bovine milk (whole, semi-skim, and skim; n = 62) and non-dairy beverages (n = 27), and we analyzed them using gas-liquid chromatography. Principal component analysis of the fatty acid data yielded 3 significant principal components, which accounted for 72% of the total variance in the data set. Principal component 1 was related to saturated fatty acids (C4:0, C6:0, C8:0, C12:0, C14:0, C17:0, and C18:0) and monounsaturated fatty acids (C14:1 cis-9, C16:1 cis-9, C17:1 cis-9, and C18:1 trans-11); whole milk samples were clearly differentiated from the rest using this principal component. Principal component 2 differentiated semi-skim milk samples by n-3 fatty acid content (C20:3n-3, C20:5n-3, and C22:6n-3). Principal component 3 was related to C18:2 trans-9,trans-12 and C20:4n-6, and its lower scores were observed in skim milk and non-dairy beverages. A cluster analysis yielded 3 groups: group 1 consisted of only whole milk samples, group 2 was represented mainly by semi-skim milks, and group 3 included skim milk and non-dairy beverages. Overall, the present study showed that a multivariate chemometric approach is a useful tool for differentiating or associating retail bovine milks and non-dairy beverages using their fatty acid profile.     

Do Urban House Prices Converge?

We investigate two aspects of housing market price dynamics. Firstly, whether the spatial pattern of house prices in a metropolitan housing market converge or diverge over time and secondly, whether suburbs with relatively low (high) house prices 20 years ago continue to occupy the same relative position in the house price distribution. The empirical work uses a property transaction database for Melbourne to examine the changing distribution of suburban house prices over a nearly 20-year period (1990–2009) that spans two housing cycles. We focus on convergence measures that use Melbourne submarket-based repeat sale house price indexes as a unit of measurement. We find that house prices diverge, and so the gap between low-priced submarkets and high-priced submarkets is increasing. A second key result is that low-priced submarkets typically remain at the low end of the house price distribution, because their rates of appreciation fall short of those at the upper end of the house price distribution. The geography of house price dynamics suggests that the price gradient with respect to distance from the central business district is becoming steeper.