Acoustic MetaMaterials (AMM) have been considered as effective means for controlling the propagation of acoustical wave energy through these materials. However, most of the currently exerted efforts are focused on studying passive metamaterials with fixed material properties. In this paper, the emphasis is placed on the development of a new class of one-dimensional acoustic metamaterials with effective bulk moduli that are programmed to vary according to any prescribed pattern along the volume of the metamaterial. Acoustic cavities coupled with either actively controlled Helmholtz or flush

Spacecraft-to-ground bistatic radar provides a straightforward method for surveying planetary surfaces on scales of importance to landers and rovers. Centimeter wavelengths, currently in use for deep-space telecommunications, interact with surface structure of similar to somewhat larger scales. For the quasi-specular component of scattering and for surfaces uniformly illuminated by monochromatic signals from an orbiting or flyby vehicle, the echo Doppler dispersion is proportional to the root mean square (rms) surface slope. When the specular condition occurs within 10°20° of the Brewster

A model that uses simulation augmented with Design of Experiments (DOE) is presented to analyse the performance of a Make-to-Order (MTO) reconfigurable manufacturing system with scalable capacity. Unlike the classical capacity scaling policies, the proposed hybrid capacity scaling policy is determined using multiple performance measures that reflect cost, internal stability and responsiveness. The impact of both tactical capacity and marketing policies and their interaction on the overall performance was analysed using DOE techniques and real case data. In addition to the different insights

One of the ultimate targets of lean manufacturing paradigm is to balance production and produce at takt time in production cells. This paper investigates the performance of a lean cell that implements the previous lean goals under uncertainty. The investigation is based on a system dynamics approach to model a dynamic lean cell. Backlog is used as a performance metric that reflects the cell's responsiveness. The cell performance is compared under certain and uncertain external (demand) and internal (machine availability) conditions. Results showed that although lean cell is expected to be

A dynamic systems approach is proposed to investigate challenges of implementing production levelling and associated costs. A model of a lean cell is developed using system dynamics. The model captures various lean tools influencing production levelling. Comparative cost analysis between various levelling implementation policies for stochastic demand with multiple products is conducted. Results showed that determining the most feasible levelling policy is highly dictated by both capacity scalability cost and limitations. The developed model and revealed insights can help lean practitioners to

This paper focuses on the design of medium access control protocols for cognitive radio networks. The scenario in which a single cognitive user wishes to opportunistically exploit the availability of empty frequency bands within parts of the radio spectrum having multiple bands is first considered. In this scenario, the availability probability of each channel is unknown a priori to the cognitive user. Hence efficient medium access strategies must strike a balance between exploring (learning) the availability probability of the channels and exploiting the knowledge of the availability

Balancing of production systems is one of the main lean manufacturing principles as it reduces in-process storage and related forms of waste. A dynamic systems approach is proposed to investigate challenges of implementing production leveling and associated costs. A lean cell producing at takt time is modeled using system dynamics. The model captures various lean tools influencing production leveling and their implications. Comparative cost analysis between various leveling implementation policies for stochastic demand with multiple products is conducted. Results showed that determining the

This study is introduced to investigate the activity of Glycine as a result of decoration with alkali metals such as Li, Na and K, and with alkaline earth metals like Be, Mg and Ca. Density functional theory (DFT) quantum mechanical calculations are performed to confirm total dipole moment (TDM), HOMO/LUMO band gap energy, electrostatic potentials (ESP) and geometrical parameters (bond length and bond angles) for all models under study. Due to the decoration, TDM increased, HOMO/LUMO band gap energy increased, molecular ESP is changed, bond length increased, and also bond angles changed due to