The generalized gradient approximation (GGA) to density functional theory (DFT) calculations indicate that the highly localized states derived from the defects of nitrogen doped carbon nanotube with divacancy (4ND-CNxNT) contribute to strong Sc and Ti bindings, which prevent metal aggregation. Comparison of the H2 adsorption capability of Sc over Ti-decorated 4ND-CNxNT shows that Ti cannot be used for reversible H2 storage due to its inherent high adsorption energy. The Sc/4ND-CNxNT possesses favorable adsorption and consecutive adsorption energy at the local-density approximation (LDA) and GGA level. Molecular dynamics (MD) study confirmed that the interaction between molecular hydrogen and 4ND-CNxNT decorated with scandium is indeed favorable. Simulations indicate that the total amount of adsorption is directly related to the operating temperature and pressure. The number of absorbed hydrogen molecules almost logarithmically increases as the pressure increases at a given temperature. The total excess adsorption of hydrogen on the (Sc/4ND)10-CNxNT arrays at 300 K is within the range set by the department of energy (DOE) with a value of at least 5.85 wt%.

One of the most useful innovations in concrete technology is Self Compacting Concrete that has the ability to flow efficiently and maintain material homogeneity. The rapid change in the behavior of concrete due to accelerating admixtures can significantly affect the workability properties of the mixture and reduce its ability to flow efficiently. To describe the influence of superplasticizers blended with accelerant on the rheological properties of SCC, several mixtures were tested for Slump Flow, L-Box, and Screen Stability tests. Artificial neural network was used to obtain a model describing the constitutive relationships between the material components and workability parameters of SCC and was optimized using Genetic Algorithm. Results showed that ANN was able to establish the relationship of rheology to the concrete material components and GA derived the optimum proportion for best rheological performance. Most of the design samples of SCC with blended superplasticizer and sodium lignosulfate accelerant were not able to perform well in the flowing ability due to inefficiency of the fresh SCC to flow. The increasing dosage of accelerant however rendered strong stability between the concrete particles allowing the SCC samples to resist segregation and maintain material homogeneity.

This paper gives an analysis of the transducer power gain and stability of a multistage, narrow-band amplifier employing nonunilateral electron devices. The amplifier is assumed to consist of n identical stages with the input and output terminations. The individual amplifier stage consists of a general active two-port device, such as the transistor, characterized by its four short-circuit admittance parameters, plus a two-terminal interstage network and an ideal coupling transformer. Both the individual amplifier stage and the over-all cascade of n amplifier stages, considered as a composite active two-port, are also characterized by their short-circuit admittance (Y) parameters. Relations between these Y parameters of the individual amplifier stage and the Y parameters of the over-all iterative amplifier have been derived. The transducer gain of the amplifier as a function of the interstage and the terminating network parameters has been studied. The transducer gain is optimized with respect to the external passive terminations and is expressed in terms of a design parameter\gamma, which is directly related to the terminating conductances of the amplifier. It is shown that for an amplifier employing inherently stable active devices, there is a value of\gammawhich gives maximum transducer power gain; for an amplifier employing potentially unstable active devices, the optimum transducer power gain of the amplifier will, in general, be a monotonically decreasing function of\gamma. In any case any prescribed value of\gammadetermines the maximum gain obtainable from the amplifier. The amplifier's margin toward instability is prescribed through prescribing a number\rho_{l}. For\rho_{l}greater than unity, the amplifier will be stable. Control of\rho_{l}is effected through appropriate choice of the design parameter\gamma. A relation relating\rho_{l}, and\gammahas been derived. Some fundamental considerations in the design of multistage, narrow-band amplifiers employing general active two-port devices are given. Results of experimental two-and three-stage transistor amplifiers are presented which show excellent agreement between the theoretical and the experimental results.