A model for flexible high-performance communication subsystems

A function-based communication model that allows applications to request individually tailored services from the communication subsystem is presented. Based on service requirements and available resources, suitable protocol machines are configured to serve the application. This configuration is done using a proper combination of functional modules. The concept of layering is therefore abandoned for both flexibility and efficiency reasons     

Electromagnetic wave shielding and microwave absorbing properties of hybrid epoxy resin/foliated graphite nanocomposites

The aim of this study is to prepare and characterize foliated graphite nanosheets (FGNs) reinforced composites based on epoxy resin for the electromagnetic wave shielding and microwave absorbing applications. The microstructure of as prepared FGNs and epoxy reinforced with different content of foliated graphite was examined by means of scanning electron microscopy and transmission electron microscopy. The effect of FGNs on thermal stability of composites was examined by thermal gravimetric. It is found that the inclusion of FGNs into the epoxy resin matrix enhances the microstructure core of epoxy resin composites. Static electric properties such as electrical conductivity, carrier mobility, number of charge carriers, and thermoelectric power of composites were studied in details. Dielectric properties of epoxy/FGN composites were characterized as a function of composition and frequency in the range of 1–18 GHz. The electromagnetic wave shielding as a function of frequency of composites was examined and compared with theoretical values. The highest shielding effectiveness was obtained for high foliated graphite loading sample FG40 at frequency of 18 GHz it equals to 62 dB. Finally, the electromagnetic wave properties such as absorption loss and reflection loss as a function of frequency were investigated. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Reduced graphene oxide: a novel black body emitter for advanced infrared decoy flares

ABSTRACT

Reduced graphene oxide (RGO) possesses unique thermal and optical properties. It could act as black body emitter with high-infrared emissivity. RGO could meet wide applications in advanced infrared decoy flares. In this study, RGO nano-sheets were synthesized through the reduction of GO after applying Hummers’ method using graphite powder as a precursor. The synthesized RGO owns 10 µm dimensions and 10 nm thicknesses. TEM analysis revealed the amorphous structure of the prepared nano-sheets. XRD diffractogram demonstrated the amorphous RGO structure. Moreover, Raman spectroscopy confirmed the complete reduction of GO into RGO. In addition, decoy flare formulations based on RGO, reactive metal fuels, and fluorocarbon polymer were developed. Additionally, thermal signature was evaluated using Arc-Optics IR spectrometer (1–6 µm) to reference formulation. Our results revealed that nanocomposite flare based on 6 wt % RGO demonstrated superior spectral intensity with an increase in average intensity by 147%. Moreover, advanced radiometric performance with superior relative intensity value (?) of 0.7 was recorded. To sum up, RGO can act as an excellent source of carbonaceous materials that can strengthen incandescence emission. Surplus magnesium could vaporize and combust with substantial heat output that could promote black body emission.     

The effect of nanoscale vanadium pentoxide on the electrical and mechanical properties of poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) loaded with vanadium pentoxide (V₂O₅) nanoparticles was successfully prepared at room temperature and ambient pressure. Transmission electron microscopy was used to characterize the final product. It was found that V₂O₅ nanoparticles were well dispersed and uniform in shape and that the diameter of the particles was confined to within 8 nm. Addition of small amounts (0.2–1 wt%) of nanoparticulate V₂O₅ to PVA increased the electrical conductivity as well as the modulus of elasticity. The deformation behaviour after preparing the nanocomposites, irrespective of V₂O₅ concentration, is similar to that of the unfilled elastomer, implying that the mechanism of large deformation is mainly governed by the matrix. Copyright © 2007 Society of Chemical Industry     

New antistatic charge and electromagnetic shielding effectiveness from conductive epoxy resin/plasticized carbon black composites

Recently, there is an increasing interest in electromagnetic interference shielding due to the rapid increase in electromagnetic pollution and the wide use of commercial and military products. Conducting polymer composites were prepared in the presence of epoxy resin and plasticized carbon black (CB). The structural characteristics of the composites were examined by means of scanning electron microscopy, cross linking density, and interparticle distance among conductive particles. The mechanical properties such as Young's modulus, elongation at break, and hardness of the composites were investigated as a function of CB content. The results indicated that CB could improve the composite microstructure. The higher mechanical behavior than green epoxy can be attributed to the interaction between CB particles and epoxy resin. The conductivity, mobility carriers, and number of charges of the composites at room temperature were found to be dependent on CB content. The applicability of the composites to antistatic charge dissipation was examined. Dependence of the microwave properties of the epoxy/CB composites on the volume fraction of CB particles and frequency were studied. Moreover the permittivity as a function of frequency of the composites was studied. The electromagnetic wave shielding of epoxy/CB composites is dominant by both reflection and absorption. Composites can find applications in antistatic charge dissipation and in suppression of electromagnetic interference and stealth technology. POLYM. COMPOS., 2008. © 2007 Society of Plastics Engineers     

Epoxy resin/plasticized carbon black composites. Part I. Electrical and thermal properties and their applications

The development of conductive polymer composites remains an important endeavor in light of growing energy concerns. A conducting polymer composite in the presence of plasticized carbon black (CB) and epoxy resin has been developed. Room temperature electrical conductivity, mobility carriers (μ), and number of charges (N) increase by increasing CB content. Electrical conductivity–temperature dependence of the composite was investigated and negative temperature coefficient of conductivity (NTC) behavior of the composites was revealed. The mechanism of the NTC effect in materials is related to the thermal expansion of the epoxy matrix and barriers height energy. The current–voltage behavior of epoxy/CB composites shows a switching effect and the mechanism of negative resistance is interpreted in details. Thermal conductivity (γ) increases with increasing filler content and the experimental data was compared with a theoretical model based on energy balance equation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers