Electrochemical Behavior of Sn‐Ag Alloys in Sodium Fluoride Solutions

Passivation and corrosion behavior on Ag, Sn and Sn‐Ag alloys were studied using various electrochemical techniques, i.e. open‐circuit, potentiodynamic polarization and impedance measurements. The specimens were polarized between –1000 and 500 mV vs. saturated calomel electrode (SCE) in naturally oxygenated NaF solution of different concentrations. The results of potentiodynamic polarization showed that each of i_corr and i_c increases with increasing either Sn% or F^‐ concentration. EIS measurements under open circuit conditions confirmed well this behavior. The effect of temperature was also studied in 0.5M NaF at temperature range of 291K to 333K. The corrosion current i_corr was observed to increase with temperature for the same electrode. The activation energy was calculated according to Arrhenius equation and its value was found to decrease considerably with increasing the Sn content in the alloy.     

Pressure vessel steels: influence of chemical composition on irradiation sensitivity

Neutron irradiation of steels used in the construction of nuclear reactor pressure vessels can lead to the embrittlement of these materials, i.e. increasing the ductile-to-brittle transition temperature and decreasing the fracture energy, which can limit the plant life. The knowledge of irradiation embrittlement and the means for minimizing such degradation is therefore important in the field of assuring the safety of nuclear power plants.

Irradiation embrittlement is quite a complex process. It involves many variables. The most important of these are irradiation temperature, neutron fluence (neutron dose), neutron flux (neutron dose rate) and chemical composition of the irradiated material. This paper is concerned with the effect of chemical composition, i.e. the role of residual and alloying elements in the irradiation embrittlement of nuclear reactor pressure vessel steels in light water reactors. It presents a critical review for the published work in this field over the last 25 years.     

Genes and Longevity of Lifespan

Aging is a complex process indicated by low energy levels, declined physiological activity, stress induced loss of homeostasis leading to the risk of diseases and mortality. Recent developments in medical sciences and an increased availability of nutritional requirements has significantly increased the average human lifespan worldwide. Several environmental and physiological factors contribute to the aging process. However, about 40% human life expectancy is inherited among generations, many lifespan associated genes, genetic mechanisms and pathways have been demonstrated during last decades. In the present review, we have evaluated many human genes and their non-human orthologs established for their role in the regulation of lifespan. The study has included more than fifty genes reported in the literature for their contributions to the longevity of life. Intact genomic DNA is essential for the life activities at the level of cell, tissue, and organ. Nucleic acids are vulnerable to oxidative stress, chemotherapies, and exposure to radiations. Efficient DNA repair mechanisms are essential for the maintenance of genomic integrity, damaged DNA is not replicated and transferred to next generations rather the presence of deleterious DNA initiates signaling cascades leading to the cell cycle arrest or apoptosis. DNA modifications, DNA methylation, histone methylation, histone acetylation and DNA damage can eventually lead towards apoptosis. The importance of calorie restriction therapy in the extension of lifespan has also been discussed. The role of pathways involved in the regulation of lifespan such as DAF-16/FOXO (forkhead box protein O1), TOR and JNK pathways has also been particularized. The study provides an updated account of genetic factors associated with the extended lifespan and their interactive contributory role with cellular pathways.     

Effect of Hydrogen Charging on the Tensile and Constant Load Properties of an Austenitic Stainless Steel Weldment

The effect of cathodic hydrogen charging on the tensile and constant load properties was determined for an austenitic stainless steel weldment comprising a 304L steel in the solution treated condition as a base metal and a 308L filler steel as a weld metal. Part of the 304L solution treatedsteel was separately given additional sensitization treatment to simulate the microstructure that would develop in the heat affected zone. Tests were performed at room temperature on notched round bar specimens. Hydrogen charging resulted in a pronounced embrittlement of the tested     

A review of recent developments in carbon capture utilizing oxy‐fuel combustion in conventional and ion transport membrane systems

Fossil fuels provide a significant fraction of the global energy resources, and this is likely to remain so for several decades. Carbon dioxide (CO₂) emissions have been correlated with climate change, and carbon capture is essential to enable the continuing use of fossil fuels while reducing the emissions of CO₂ into the atmosphere thereby mitigating global climate changes. Among the proposed methods of CO₂ capture, oxyfuel combustion technology provides a promising option, which is applicable to power generation systems. This technology is based on combustion with pure oxygen (O₂) instead of air, resulting in flue gas that consists mainly of CO₂ and water (H₂O), that latter can be separated easily via condensation, while removing other contaminants leaving pure CO₂ for storage. However, fuel combustion in pure O₂ results in intolerably high combustion temperatures. In order to provide the dilution effect of the absent nitrogen (N₂) and to moderate the furnace/combustor temperatures, part of the flue gas is recycled back into the combustion chamber. An efficient source of O₂ is required to make oxy‐combustion a competitive CO₂ capture technology. Conventional O₂ production utilizing the cryogenic distillation process is energetically expensive. Ceramic membranes made from mixed ion‐electronic conducting oxides have received increasing attention because of their potential to mitigate the cost of O₂ production, thus helping to promote these clean energy technologies. Some effort has also been expended in using these membranes to improve the performance of the O₂ separation processes by combining air separation and high‐temperature oxidation into a single chamber. This paper provides a review of the performance of combustors utilizing oxy‐fuel combustion process, materials utilized in ion‐transport membranes and the integration of such reactors in power cycles. The review is focused on carbon capture potential, developments of oxyfuel applications and O₂ separation and combustion in membrane reactors. The recent developments in oxyfuel power cycles are discussed focusing on the main concepts of manipulating exergy flows within each cycle and the reported thermal efficiencies. Copyright © 2010 John Wiley & Sons, Ltd.     

Numerical experiments with two-dimensional elastic-viscoplastic bars

Numerical solutions of two-dimensional elastic-viscoplastic wave propagation in bars of various shapes are discussed. Hondo code with the addition of a new sub-program for Bodner-Partom's constitutive equation is used for the analysis. For a two-dimensional elastic bar and a one-dimensional elastic/linear-hardening plastic bar, Hondo numerical results agree well with available analytical or numerical solutions. For elastic-viscoplastic bar, numerical solutions show some interesting features of the dynamic responses. The responses for Bodner-Partom constitutive equation were found to lie between the results for elastic-plastic and purely elastic constitutive relation. The precursor wave always propagates at the speed of elastic wave. For a bar with both discontinuities of cross-section and material properties, the computation showed the disappearance of stress localization, which usually exists for single-material bar with a geometric discontinuity.     

Efficient Data Compression of ECG Signal Based on Modified Discrete Cosine Transform

This paper introduced an efficient compression technique that uses the compressive sensing (CS) method to obtain and recover sparse electrocardiography (ECG) signals. The recovery of the signal can be achieved by using sampling rates lower than the Nyquist frequency. A novel analysis was proposed in this paper. To apply CS on ECG signal, the first step is to generate a sparse signal, which can be obtained using Modified Discrete Cosine Transform (MDCT) on the given ECG signal. This transformation is a promising key for other transformations used in this search domain and can be considered as the main contribution of this paper. A small number of wavelet components can describe the ECG signal as related work to obtain a sparse ECG signal. A sensing technique for ECG signal compression, which is a novel area of research, is proposed. ECG signals are introduced randomly between any successive beats of the heart. MIT-BIH database can be represented as the experimental database in this domain of research. The MIT-BIH database consists of various ECG signals involving a patient and standard ECG signals. MATLAB can be considered as the simulation tool used in this work. The proposed method's uniqueness was inspired by the compression ratio (CR) and achieved by MDCT. The performance measurement of the recovered signal was done by calculating the percentage root mean difference (PRD), mean square error (MSE), and peak signal to noise ratio (PSNR) besides the calculation of CR. Finally, the simulation results indicated that this work is one of the most important works in ECG signal compression.     

A new technique for numerical simulation of dendritic solidification using a meshfree interface finite element method

A new technique for sharp‐interface modeling of dendritic solidification is proposed using a meshfree interface finite element method such that the liquid–solid interface is represented implicitly and allowed to arbitrarily intersect the finite elements. At the interface‐embedded elements, meshfree interface points without connectivity are imposed directly at the zero level set while meshfree interpolants are constructed using radial basis functions. This ensures both the partition of unity and the Kronecker delta properties are satisfied allowing for precise and easy imposition of Dirichlet boundary conditions at the interface. The constructed meshfree interpolants are also used for solving a variational level set equation based on the Ginzburg–Landau energy functional minimization such that reinitialization is completely eliminated and fast marching algorithms for interfacial velocity extension are not necessary resulting in an efficient algorithm with excellent volume conservation. The meshfree interface finite element method is used for modeling dendritic solidification in a pure melt where it is found suitable in handling the complex interfacial dynamics often encountered in dendritic growth. Mathematical formulation and implementation followed by numerical results and analysis will be presented and discussed. Copyright © 2016 John Wiley & Sons, Ltd.     

Characterizing game dynamics in two-player strategy games using network motifs.

Many complex systems, whether biological, sociological, or physical ones, can be represented using networks. In these networks, a node represents an entity, and an arc represents a relationship/constraint between two entities. In discrete dynamics, one can construct a series of networks with each network representing a time snapshot of interaction among the different components in the system. Understanding these networks is a key to understand the dynamics of real and artificial systems. Network motifs are small graphs-usually three to four nodes-representing local structures. They have been widely used in studying complex systems and in characterizing features on the system level by analyzing locally how the substructures are formed. Frequencies of different network motifs have been shown in the literature to vary from one network to another, and conclusions hypothesized that these variations are due to the evolution/dynamics of the system. In this paper, we show for the first time that in strategy games, each game (i.e., type of dynamism) has its own signature of motifs and that this signature is maintained during the evolution of the game. We reveal that deterministic strategy games have unique footprints (motifs' count) that can be used to recognize and classify the game's type and that these footprints are consistent along the evolutionary path of the game. The findings of this paper have significance for a wide range of fields in cybernetics.