Re‐calibration of Engelmaier's Model for Leadless,Lead‐free Solder Attachments

In this paper, the solder attachment fatigue model created by Werner Engelmaier is re‐calibrated in order to make it applicable in conjunction with leadless, lead‐free solder attachments. Sn3.8Ag0.7Cu solder attached ball‐grid‐array components are addressed to three thermal cycling test profiles. Based on the results, both physical and statistical parameters are obtained and compared with the values relevant to tin–lead solder assemblies. The validity of the statistical distribution selection (two‐parameter Weibull) is studied. Acceleration factors correlating different test profiles are obtained, and they are found to be only weakly dependent on the test vehicle type. Copyright © 2006 John Wiley & Sons, Ltd.     

A genetic programming method for protein motif discovery and protein classification

Proteins can be grouped into families according to some features such as hydrophobicity, composition or structure, aiming to establish common biological functions. This paper presents MAHATMA—memetic algorithm-based highly adapted tool for motif ascertainment—a system that was conceived to discover features (particular sequences of amino acids, or motifs) that occur very often in proteins of a given family but rarely occur in proteins of other families. These features can be used for the classification of unknown proteins, that is, to predict their function by analyzing their primary structure. Experiments were done with a set of enzymes extracted from the Protein Data Bank. The heuristic method used was based on genetic programming using operators specially tailored for the target problem. The final performance was measured using sensitivity, specificity and hit rate. The best results obtained for the enzyme dataset suggest that the proposed evolutionary computation method is effective in finding predictive features (motifs) for protein classification.     

Reconfiguring flexible machine modules of a PCB assembly line

Assembly of electronic components to Printed Circuit Boards (PCB) is a complicated manufacturing process and therefore its control is usually divided into several subtasks which are handled separately. We consider the combined task of determining a machine configuration and line balancing for a single assembly line of interconnected, reconfigurable machine modules and one PCB type in production. The modules can be tailored to the needs of each PCB type by suitable assignments for placement heads, nozzles and feeders. Out of these, the component-to-machine assignment appears to be most difficult and we propose five different solution methods for it; brute force, random, greedy, local search and genetic algorithm. The genetic algorithm outperformed the other methods in practical test.     

Analysis of regioisomers of triacylglycerols of northern currant seed oil by tandem mass spectrometry

Currant oils have special health properties due to their moderate contents of α‐linolenic, γ‐linolenic and stearidonic acids. The distribution of fatty acids (FA) in the triacylglycerols (TAG) may affect the beneficial effects. Seed oils of wild northern red currant (NRC) (Ribes spicatum L.) from Northern Finland and of wild alpine currant (AC) (R. alpinum L.) from the South‐West coast of Finland were investigated. The purified TAG were analysed by tandem mass spectrometry by applying the ammonia negative ion chemical ionisation – collision‐induced dissociation method. Molecular weight fractions rich in C18:3 FA and C18:4 FA were investigated. Of the total oil, the molecular weight species 54:7 (ACN:DB), 54:8 and 54:9 were more abundant in NRC than in AC, being 21.0%, 15.8%, 7.4% and 16.2%, 11.2%, 4.8%, respectively (p <0.05). The species 52:6 was more abundant in AC (3.1%) than in NRC (2.6%) (p <0.05). The preferential order of FA to be in the sn‐2 position in both berries was typically C18:1 > C18:2 > C18:4 > C18:3. No difference was observed between relative locations of C16:0 FA and C18:3 FA in either of the oils. Within the TAG consisting of FA combinations C18:3/C18:3/C18:1 (54:7), C18:1 was more preferentially in the sn‐2 position (p <0.05) in AC (93.2%) than in NRC (74.6%), and in the case of C18:3, the preference was vice versa. Within the molecular weight species 54:9, FA combination C18:4/C18:3/C18:2, linoleic acid preferentially occupied the secondary position (p <0.005) in both berries, and the proportion of the TAG regioisomer pair sn‐C18:3‐C18:4‐C18:2 + sn‐C18:2‐C18:4‐C18:3 was more abundant (30.2%) in NRC than in AC (15.3%). Within the TAG species 52:6, proportions of all the existing combinations, C16:0/C18:3/C18:3, C16:0/C18:4/C18:2 and C16:1/C18:3/C18:2, varied between the two berry species (p <0.005).     

Experimental compaction characterization of unidirectional stitched noncrimp fabrics in the vacuum infusion process

In this study, experimental test equipment developed in‐house was used to study the compaction behavior of stitched quasi‐unidirectional (UD) non‐crimp fabrics (NCF) during the pre‐filling, filling, and post‐filling stages of the vacuum infusion (VI) process. The effects of the stitch pattern, stitch tension, and fiber sizing of reinforcements, as well as the effect of nesting of fiber bundles in neighboring layers, were studied. Moreover, the effects of cyclic compaction, resin viscosity, and different post‐filling strategies were studied. The developed experimental test equipment provided an applicable measuring method for characterizing the compaction behavior of both the dry and resin‐impregnated reinforcements. The effects of the stitching parameters and fiber nesting of reinforcements were found. The stitch pattern and post‐filling strategies were noted to have an effect on the preform and laminate thickness. POLYM. COMPOS., 37:2692–2704, 2016. © 2015 Society of Plastics Engineers     

Prospecting hydrogen production of Escherichia coli by metabolic network modeling

Genome-scale model was applied to analyze the anaerobic metabolism of Escherichia coli. Three different methods were used to find deletions affecting fermentative hydrogen production: flux balance analysis (FBA), algorithm for blocking competing pathways (ABCP), and manual selection. Based on these methods, 81 E. coli mutants possessing one gene deletion were selected and cultivated in batch experiments. Experimental results of H₂ and biomass production were compared against the results of FBA. Several gene deletions enhancing H₂ production were found. Correctness of gene essentiality predictions of FBA for the selected genes was 78% and 77% in glucose and galactose media, respectively. 33% of the mutations that were predicted by FBA to increase H₂ production had a positive effect in experiments. Batch cultivation is a simple and straightforward experimental way to screen improvements in H₂ production. However, the ability of FBA to predict the H₂ production rate cannot be evaluated by batch experiments. Metabolic network models provide a method for gaining broader understanding of the complicated metabolic system of a cell and can aid in prospecting suitable gene deletions for enhancing H₂ production.     

Role of transverse temperature gradients in the generation of lamellar eutectic solidification patterns

In directional solidification, a sample is pulled in an externally imposed temperature gradient. When the pulling direction and the temperature gradient are not perfectly aligned, a transverse temperature gradient is generated in the sample. We investigate the dynamics of lamellar eutectic patterns, both by experimental observations and by numerical simulations, and find that it is dramatically affected by a transverse gradient. Whereas, in its absence, the labyrinth patterns that are formed in the initial stage of solidification persist over the entire duration of the experiments, a transverse temperature gradient induces a drift of the pattern which rapidly generates a regular array of lamellae. The drift speed is found to be consistently larger than expected from the normal growth hypothesis, both in simulations and experiments.     

Elution factors of synthetic oxotriacylglycerols as an aid in identification of peroxidized natural triacylglycerols by reverse-phase high-performance liquid chromatography with electrospray mass spectrometry

Selected elution factors were determined for model oxotriacylglycerols as an aid in identification of the peroxidation products of natural triacylglycerols by reverse-phase high-performance liquid chromatography (HPLC) with electrospray mass spectrometry (LC/ES/MS). For this purpose synthetic triacylglycerols of known structure were converted to hydroperoxides, hydroxides, epoxides, and core aldehydes and their dinitrophenylhydrazones by published procedures. The oxotriacylglycerols were resolved by normal-phase thin-layer chromatography and reverse-phase HPLC, and the identities of the oxotriacylglycerols confirmed by LC/ES/MS. Elution factors of oxotriacylglycerols were determined in relation to a homologous series of saturated triacylglycerols, ranging from 24 to 54 acylcarbons, and analyzed by reverse-phase HPLC, using a gradient of 20–80% isopropanol in methanol as eluting solvent and an evaporative light-scattering detector. It was shown that the elution times varied with the nature of the functional group and its regiolocation in the triacylglycerol molecule. A total of 31 incremental elution factors were calculated from chromatography of 33 oxygenated and nonoxygenated triacylglycerol species, ranging in carbon number from 36 to 54 and in double-bond number from 0 to 6.