Comparison of geometric optics approximation and integral method for reflection and transmission from microgeometrical dielectric surfaces

The effects of incidence angle, geometrical shape, and optical properties of dielectric rough surfaces on reflectivity and transmissivity are discussed. Radiative properties for various surface geometries are calculated. Since the integral method is computationally expensive, a geometric optics approximation is developed. The regions of validity of the approximation compared with the integral method are quantified. Curves are presented that show these radiative properties versus the correlation length at incidence angle for a fixed rms deviation of the surface. The surface geometry, incidence angle, multiple scattering, shadowing effects, and dielectric permittivity contributions to the domains of validity of the approximation method are discussed for both TE and TM polarizations.     

Two-dimensional phase unwrapping using a hybrid genetic algorithm

A novel hybrid genetic algorithm (HGA) is proposed to solve the branch-cut phase unwrapping problem. It employs both local and global search methods. The local search is implemented by using the nearest-neighbor method, whereas the global search is performed by using the genetic algorithm. The branch-cut phase unwrapping problem [a nondeterministic polynomial (NP-hard) problem] is implemented in a similar way to the traveling-salesman problem, a very-well-known combinational optimization problem with profound research and applications. The performance of the proposed algorithm was tested on both simulated and real wrapped phase maps. The HGA is found to be robust and fast compared with three well-known branch-cut phase unwrapping algorithms.     

Energy and output dynamics in Bangladesh

The relationship between energy consumption and output is still ambiguous in the existing literature. The economy of Bangladesh, having spectacular output growth and rising energy demand as well as energy efficiency in recent decades, can be an ideal case for examining energy-output dynamics. We find that while fluctuations in energy consumption do not affect output fluctuations, movements in output inversely affect movements in energy use. The results of Granger causality tests in this respect are consistent with those of innovative accounting that includes variance decompositions and impulse responses. Autoregressive distributed lag models also suggest a role of output in Bangladesh's energy use. Hence, the findings of this study have policy implications for other developing nations where measures for energy conservation and efficiency can be relevant in policymaking.     

Spectrally correlated radiation and laminar forced convection in the entrance region of a circular duct

The two-dimensional combined radiative and convective transfer in emitting and absorbing real gases in the entrance region of a duct with a jump of wall temperature is studied. The axial propagation of radiation is taken into account in the analysis. The flow field and the energy equations are solved simultaneously and the radiative properties of the flowing gases, CO₂ or H₂O, are modeled by using either the narrow-band correlated-k model or the global absorption distribution function (ADF) model. The results are presented in terms of temperature and radiative power fields, and of the evolution of bulk temperatures and of heat transfer coefficients. Due to the axial component of the radiative flux, the gas is preheated or precooled before the change in wall temperature and this induces a persistent difference between the results of 1-D and 2-D radiation analyses. Some differences between CO₂ and H₂O temperature and radiative power profiles, due to the different structures of their spectra, are put in evidence. The ADF model, only suitable for gray walls, is shown to be less accurate when the gas is heated than when it is cooled.     

On the Throughput Capacity of Cooperative Multi-hop Wireless Ad hoc Networks with Multi-flow

Cooperative relaying techniques are known to provide spatial diversity for wireless fading channels. In contrast to non-cooperative transmission (direct transmission), they increase link reliability, provide higher capacity, reduce transmit power, and extend transmission range. Mostly the gains of cooperative relaying are shown for single flow scenarios in the absence of inter-flow interference. In this paper we study the effect of inter-flow interference on the capacity of cooperative networks in multi-hop multi-flow settings. We used the conflict graph to model the interference and find the additional constraints introduced due to cooperative transmission by using the concept of cliques on the conflict graph, which can be used to capture the interference relation among links. We formulated the multi-commodity flow problem for network capacity using linear programming, and employed a clique based analysis of the conflict graph to compute interference constraints. It is observed that the throughput drops significantly when cooperative transmissions are used in the network. We also found that the hop counts increase when cooperative links are used that is due to avoiding interfering links, which results in losing the benefits of shortest-path routing.     

Effect of Zn Substitution on the Structural and Physical Properties of Delafossite-Type Oxide CuCrO2

In this paper, we report the effect of non-magnetic Zn-doped CuCrO₂. The structure, Raman spectroscopy, magnetic properties, dielectric permittivity, and electric polarization have been investigated. The incorporation of Zn²⁺ generates very anisotropic microstrains in the structure. The temperature dependence of magnetic susceptibly for all samples exhibits a magnetic dilution and paramagnetic behavior at high temperature. It is argued that non-magnetic substitution destabilizes the antiferromagnetic order of Cr³⁺ ions and modulates the spin configuration. The coupling between the magnetic order, dielectric permittivity and polarization is also characterized.     

Multi-hop routing with cooperative transmission: a cross-layer approach

Cooperative diversity techniques have received a lot of attention recently due to their ability to provide spatial diversity in fading wireless environment without the requirement of implementing multiple antenna on the same device. It increases link reliability, provides higher capacity, reduces transmit power, and extends transmission range for the same level of performance and modulation rate. In this paper, we study the achievable gain of cooperative communications from a wireless cross-layer point of view in multi hop networks. We propose two routing algorithms applicable for wireless ad hoc networks. First, we propose an edge node based on a greedy cooperative routing (ENBGCR) algorithm, where we modify the geographic routing algorithm to incorporate the cooperative transmission and extend the coverage range of the nodes. The main objective of ENBGCR algorithm is to minimize the number of hops that messages transverse to reach their destination. Then the energy-efficient cooperative routing algorithm is proposed to minimize the end-to-end total transmission power subject to end-to-end target data rate. Simulation results for both algorithms show that the proposed strategies have great improvement in terms of delay and power saving respectively for the same quality of service requirement as compared to traditional algorithms.     

Compartmentalization Role of A-Kinase Anchoring Proteins (AKAPs) in Mediating Protein Kinase A (PKA) Signaling and Cardiomyocyte Hypertrophy

The Beta-adrenergic receptors (β-ARs) stimulation enhances contractility through protein kinase-A (PKA) substrate phosphorylation. This PKA signaling is conferred in part by PKA binding to A-kinase anchoring proteins (AKAPs). AKAPs coordinate multi-protein signaling networks that are targeted to specific intracellular locations, resulting in the localization of enzyme activity and transmitting intracellular actions of neurotransmitters and hormones to its target substrates. In particular, mAKAP (muscle-selective AKAP) has been shown to be present on the nuclear envelope of cardiomyocytes with various proteins including: PKA-regulatory subunit (RIIα), phosphodiesterase-4D3, protein phosphatase-2A, and ryanodine receptor (RyR2). Therefore, through the coordination of spatial-temporal signaling of proteins and enzymes, mAKAP controls cyclic-adenosine monophosphate (cAMP) levels very tightly and functions as a regulator of PKA-mediated substrate phosphorylation leading to changes in calcium availability and myofilament calcium sensitivity. The goal of this review is to elucidate the critical compartmentalization role of mAKAP in mediating PKA signaling and regulating cardiomyocyte hypertrophy by acting as a scaffolding protein. Based on our literature search and studying the structure–function relationship between AKAP scaffolding protein and its binding partners, we propose possible explanations for the mechanism by which mAKAP promotes cardiac hypertrophy.