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In the present study, hybrid composites are prepared by reinforcing various concentrations of high permittivity zirconia nanofiller into epoxy/CNT compositions to test their usability in EMI shielding applications in the X and Ku bands. ZrO2 nanofiller is added in different proportions to improve absorbance shielding while maintaining the composite conductivity uniform by adding constant CNT concentration to restrict the reflectance shielding. The microscopic studies have revealed an efficient dispersion of ZrO2 nanoparticles in the CNT networks and provided a smoother surface. The presence of zirconia nanofillers increased the dielectric properties, viz. the dielectric constant (194 at 0.1 Hz) and loss tangent (1.57 at 0.1 Hz), respectively, whereas the conductivity was found to be invariantly constant. The increased permittivity of composites enhanced the shielding by absorption, while the shielding by reflection is least influenced by the addition of zirconia nanofiller. The addition of zirconia nanofillers increased the permittivity and tan delta, allowing charges to accumulate at the interfacial areas for incoming EM radiations, resulting in increased absorbance shielding. Limiting the CNT concentration in all composites to the same level resulted in the formation of conductive networks, thus resulting in uniform reflectance shielding for all the hybrid composites in the present study. The dynamic mechanical analysis showed the improvement in the storage modulus and activation energy due to the enhanced interfacial adhesion and cross-linked polymer density.

Amorphous carbon films were deposited successfully on Cu foils by DC magnetron sputtering technique. Electrochemical performance of the film as lithium battery anode was evaluated across Li metal at 0.2 C rate in a non-aqueous electrolyte. The discharge curves showed unusually low irreversible capacity in the first cycle with a reversible capacity of ∼810 mAh g−1, which is at least 2 times higher than that of graphitic carbon. For the first time we report here an amorphous carbon showing such a high reversibility in the first cycle, which is very much limited to the graphitic carbon. The deposited films were extensively characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and step profilometer for the structural and surface properties. The hydrogen content of the synthesized films was studied using residual gas analysis (RGA). The low hydrogen content and the low specific surface area of the synthesized amorphous carbon film are considered responsible for such a high first cycle columbic efficiency. The growth mechanism and the reasons for enhanced electrochemical performance of the carbon films are discussed.

The self-collimation effect in photonic crystal is used for the realization of open cavity resonator formed by photonic prisms in a four-port arrangement. The confinement, field enhancement and energy storage capabilities of the proposed cavity are explored in this paper. The effect of dielectric losses included in the system and role of the position of line source in the confinement effect of the cavity are brought out. Decay of short Gaussian pulse placed inside the cavity is analyzed through finite-difference time-domain studies. Due to the high confinement and divergence less beam propagation, utility of the proposed cavity for rotational gyroscope application is also revealed.

Carbon nanotubes (CNTs) are considered to be excellent candidates for high performance electrode materials in Li ion batteries. The nanometer-sized pore structures of CNTs can provide the hosting sites for storing large numbers of Li ions. A short diffusion distance for the Li ions may bring about a high discharge rate. The long-cycle performance of aligned multiwalled carbon nanotubes (MWNTs) directly synthesized on stainless-steel foil as an anode material in lithium battery is demonstrated. An increase in the specific capacity with an increase in the cycle number is observed. Starting at a value of 132 mA hg -1 in the first cycle at a current rate of 1 C, the specific capacity increased about 250% to a value of 460 mA hg -1 after 1 200 cycles. This is an unusual but a welcoming behavior for battery applications. It is found that the morphology of the MWNTs with structural and surface defects and the stainless-steel substrate play an important role in enhancing the capacity during the cycling process.

Manganese oxides have been synthesized by a variety of techniques in different nanostructures and studied for their properties as electrode materials in two different storage applications, supercapacitors (SCs) and Li-ion batteries. The composites involving carbon nanotubes (CNTs) and manganese oxides were also prepared by a simple room-temperature method and evaluated as electrode materials in the above applications. The synthesis of nanostructured manganese oxides was carried out by simple soft chemical methods without any structure directing agents or surfactants. The prepared materials were well characterized using different analytical techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), surface area studies, etc. The electrochemical properties of the nanostructured manganese oxides and their composites were studied using cyclic voltammetry (CV), galvanostatic charge-discharge, and electrochemical impedance spectroscopic (EIS) studies. The influence of structural/surface properties on the electrochemical performance of the synthesized manganese oxides is reviewed.

Cyber-Physical Systems (CPS) is a relatively novel computing paradigm where there is a tight integration of communications, computation, and the physical environment. An important component of the CPS devices is the sensors they use to interact with each other and the physical world around them. With CPS applications, engineers monitor the structural health of highways and bridges, farmers check the health of their crops, and ecologists observe wildlife in their natural habitat. Nonetheless, current security models consider protecting only networking components of the CPS devices utilizing traditional security mechanisms (e.g., an intrusion detection system for the data that traverse the network protocol stacks). The protection mechanisms are not sufficient to protect CPS devices from threats emanating from sensory channels. Using sensory channels (e.g., light, temperature, infrared), an adversary can successfully attack systems. Specifically, the adversary can (1) trigger existing malware, (2) transfer malware, or (3) combine malicious use of different sensory channels to increase the impact of the attack on CPS devices. In this work, we focus on these novel sensory channel threats to CPS devices and applications. We first note how sensory channel threats are an emerging area for the CPS world. Then, we analyze the performance various sensory channel threats. Moreover, using an iRobot Create as our CPS platform, we exploit simple vulnerable programs on iRobot through its infrared channel. Finally, we introduce the design of a novel sensory channel aware intrusion detection system as a protection mechanism against the sensory channel threats for CPS devices.

Using solid-state reaction route and high-energy ball milling technique Zn 1-xMg xTiO 3 (x = 0-0.5) compositions were synthesized. These ball milled samples were sintered at 1100�C for 2 h and microwave dielectric properties such as dielectric constant (?'), quality factor (Q), and temperature coefficient of resonant frequency (? f) were studied. Significant improvement in quality factor of ? 65% was observed for x = 0.3. To understand the effect of sintering duration on the microwave dielectric properties, single phase Zn 0.7Mg 0.3TiO 3 samples were sintered at 1100�C for different durations from 2 to 20 h. The grain size increases with sintering duration and it influences to enhance the microwave dielectric properties and as a result, the quality factor further improved by three times. The dielectric constant and temperature coefficient of resonant frequency showed a slight improvement of ? 10%-15% with sintering duration. � 2012 The American Ceramic Society.

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