Study on properties of Sn–9Zn–Ga solder bearing Nd

The effects of Nd on wettability, microstructure and mechanical properties of Sn–9Zn–Ga–xNd lead-free solder were investigated. The results indicate that adding moderate amount of rare earth Nd, the wettability as well as mechanical properties of Sn–9Zn–0.5Ga solder were evidently improved, and when the content of Nd is at 0.08 wt%, the best wettability and comprehensive properties of soldered joint were obtained. It was also found that the addition of rare earth Nd could refine the microstructure of the solder, but some dark NdSn₃ phase appeared when the addition of Nd exceeded 0.15 wt%. Moreover, the IMCs thickness at the solder/Cu interface was reduced with the addition of Nd which gave a favorable influence on the mechanical property of the soldered joints.     

Optimization issues of the broke management system in papermaking

This paper presents an optimization strategy for the design and operation of a broke management system in a papermaking process. A stochastic model based on a two-state Markov process is presented for the broke system and a multiobjective and bi-level stochastic optimization model is developed featuring (i) a multiobjective operational subproblem for the optimization of the broke dosage and (ii) a multiobjective design problem formulation. An efficient optimization strategy is proposed for the operational subproblem along with a simulation based Pareto optimal solution for the design problem, and illustrated with a detailed case study.     

The effects of Cu2+ and La3+ doping on the sintering ability of sol-gel derived high silica bioglasses

This paper reports the hierarchical influence of co-doping copper and lanthanum in a sol–gel derived quaternary (Si, Ca, Na, P) bioactive glass on its sintering ability. The mutual effects of Cu & La on density, crystallisation and sinterability were investigated using Taguchi analysis. Thermal properties of bioglasses were assessed by DTA/TGA and dilatometry, while crystallisation phase evolution of was monitored by X–ray diffraction. Ten glass compositions were sintered at two temperatures (800 and 900?°C). The glass structure was analysed by MAS–NMR, the sintered density measured, and sintered microstructures observed by SEM/EDS. Results revealed that Cu promotes early densification, enhancing density at lower sintering temperatures. Oppositely, beneficial sintering effects of La might be observed at higher sintering temperatures (>1000?°C). These differences are induced by the distinct roles of doping elements on devitrification upon increasing their concentrations: crystallisation is promoted by Cu and is inhibited by La.     

Composition and microstructure of Na0.5Bi0.5TiO3 ceramics with excess Bi

In the present work, Na_0.5Bi_0.5TiO₃ (NBT) ceramics with the addition of excess Bi in two different ways – before calcination and before sintering – are considered, revealing how the excess Bi affects their microstructure and chemical content. Average grain size is seen to decrease, with the grain size distribution becoming less diffused at higher excess Bi concentrations. The reason for such a feature is the shift of the sintering temperature region where the abnormal grain growth starts to contribute towards higher temperatures. The influence of excess Bi is more pronounced in the case if it is added before calcination. It was discovered that a small amount of excess Bi helps to prevent the formation of Bi-deficient inclusions. While, high concentrations of excess Bi induce the formation of Bi-rich inclusions – most probably Na_0.5Bi_4.5Ti₄O₁₅. Possible mechanisms of formation of both types of inclusions are discussed in detail. Instead of Bi over-stoichiometry, elevated Na content and slightly lower O content were detected in the matrix grains of the sintered NBT ceramics prepared with excess Bi. These deviations increase upon increasing the added excess Bi concentration. The presence of another, Na-rich phase, is assumed, which could not be detected by X-ray diffraction or by energy-dispersive X-ray analysis.     

Crack dynamics in a nonlinear lattice

A discrete two-dimensional square-cell lattice with a steady propagating crack is considered. The lattice particles are connected by massless bonds, which obey a piecewise-linear double- humped stress–strain relation. Initially, Hooke’s law is valid as the first stable branch of the force–elongation diagram; then, as the elongation becomes critical, the transition to the other branch occurs. Further, when the strain reaches the next critical value, the bond breaks. This transition is assumed to occur only in a line of the breaking bonds; the bonds outside the crack line are assumed to be in the initial branch all the time. The formulation relates to the crack propagation with a ‘damage zone’ in front of the crack. An analytical solution is presented that allows to determine the crack speed as a function of the far-field energy release rate, to find the total speed-dependent dissipation, and to estimate the role of the damage zone. The analytical formulation and the solution present a development of the previous ones for the crack and localized phase transition dynamics in linear and bistable-bond lattices.     

Destruction of Helminth (Ascaris suum) Eggs by Ozone

Based on the properties of ozone as a strong germicidal agent, the inactivation kinetics or disintegration of Ascaris suum eggs in water were studied. Ozone was applied in synthetic samples, the concentration of dissolved ozone in the liquid phase was typically between 3.5 to 4.7mg/L, pH 5, 9. The value of 90% inactivation (t₉₀) obtained was at 1 h, the remaining 10% being inactivated in 2 h. A linear correlation between the logarithm of bacterial or yeast concentration (N) and contact time was found, being the linear significant correlation coefficient (r of 0.95). That 2-log inactivation occurred at a CT value near 4.7mg/min/L. The best reduction percentage was of 99.00 in 120min. It therefore could be demonstrated that ozone indeed induces effects on the helminth eggs.     

Effect of Multiwalled Carbon Nanotubes on the Properties of EPDM/NBR Dissimilar Elastomer Blends

In the presence of multiwalled carbon nanotubes (MWCNT), polar nitrile-butadiene rubber (NBR) and nonpolar ethylene propylene diene rubber (EPDM) blends were prepared following a melt mixing method. For the preparation of MWCNT filled EPDM/NBR blends, two mixing methods were used: direct mixing and the masterbatch dilution method. Various physical, mechanical, and morphological properties are explored to elucidate the dispersion behavior of MWCNTs. It was concluded that the preparation method influences the dispersion of the nanotubes in different rubber phases and the properties of these blends are controlled by the degree of dispersion of the nanotubes in the two phases.     

A New Hybrid Fault-Tolerant Architecture for Digital CMOS Circuits and Systems

This paper presents a new hybrid fault-tolerant architecture for robustness improvement of digital CMOS circuits and systems. It targets all kinds of errors in combinational part of logic circuits and thus, can be combined with advanced SEU protection techniques for sequential elements while reducing the power consumption. The proposed architecture combines different types of redundancies: information redundancy for error detection, temporal redundancy for soft error correction and hardware redundancy for hard error correction. Moreover, it uses a pseudo-dynamic comparator for SET and timing errors detection. Besides, the proposed method also aims to reduce power consumption of fault-tolerant architectures while keeping a comparable area overhead compared to existing solutions. Results on the largest ISCAS’85 and ITC’99 benchmark circuits show that our approach has an area cost of about 3 % to 6 % with a power consumption saving of about 33 % compared to TMR architectures.