Some aspects of microstructural and dielectric properties of nanocrystalline CdS/poly(vinylidene fluoride) composite thin films

Free‐standing flexible composite films of nanocrystalline cadmium sulfide‐impregnated poly(vinylidene fluoride) (nano‐CdS/PVDF) were prepared using a sol–gel technique. The effect of CdS loading, in the PVDF host matrix, on the dielectric properties was studied. An increase in dielectric constant (more than 10 times) was observed in the films when poled under an electric field. The composite films were also characterized using microstructural, Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy measurements. © 2015 Society of Chemical Industry     

Optical trapping with modified exponential decay in optical waveguides via dressed continuum

Simultaneous interaction of two side-coupled waveguides with the dressed continuum represented by a linear waveguide array causes cross-coupling between the two evanescent decay-channels and results in the phenomenon of trapping of the light field in the spatial domain during propagation through the waveguide system. For specific parameter values, it has been shown that the trapping effect is possible for all relative positions of the waveguides side-coupled to the dressed continuum. The model also demonstrates non-exponential decay characteristics of the optical field amplitudes in the waveguides. Depending on the values of the propagation mismatch, the nonlinearity arising in the decay-rate characteristics exhibits features like optical Zeno and anti-Zeno effects.     

Optimization of a rapid dot-blot immunoassay for detection of Salmonella enterica serovar Enteritidis in poultry products and environmental samples

An immunoassay was developed for the detection of Salmonella serovar Enteritidis in poultry and environmental samples. This assay consisted of a two-step procedure that involved an enrichment step using whole egg homogenate (EH) as the enrichment medium and detection by a monoclonal antibody (MAb)-based dot-blot assay. Egg homogenate enriched Salmonella Enteritidis was heated to 100°C for 10 min in the presence of cholic acid, a detergent, to liberate the lipopolysaccharide (LPS) antigen in gelled egg matrix. This was subsequently transferred onto a nitrocellulose membrane for detection with MAb 2F11. Several commercially available media were compared with egg homogenate for their relative ability to resuscitate and propagate Salmonella Enteritidis to detectable levels. Incubation in EH, trypticase soy broth (TSB), and lactose broth (LB) resulted in comparable levels of Salmonella Enteritidis as demonstrated by viable plate counts. Salmonella Enteritidis grown in TSB exhibited the greatest visual intensity showing a positive test when tested by the dot-blot assay. Incubation time necessary to detect one cfu of Salmonella Enteritidis was reduced from 20 to 10 h using TSB as the enrichment broth. Addition of ferrous sulphate or ferrioxamine E or cholic acid in the enrichment broth had negligible negative effects on the growth of Salmonella. Salmonella Enteritidis when incubated with a mixture of naturally contaminated or artificially inoculated competitive micro-organisms in environmental samples at a ratio of 1:10², was able to reproduce to detectable numbers for the immunoassay. This method was able to detect all phage types (PT 1, 6, 7, 8, 13, 13a, 14b, 21 and 28) with unique ribopatterns. The results demonstrated that Salmonella Enteritidis, when preenriched in a medium containing ferrous sulphate or cholic acid, could be readily detected in the presence of 100-fold higher competition of other micro-organisms.     

Security Against Hardware Trojan Attacks Using Key-Based Design Obfuscation

Malicious modification of hardware in untrusted fabrication facilities, referred to as hardware Trojan, has emerged as a major security concern. Comprehensive detection of these Trojans during post-manufacturing test has been shown to be extremely difficult. Hence, it is important to develop design techniques that provide effective countermeasures against hardware Trojans by either preventing Trojan attacks or facilitating detection during test. Obfuscation is a technique that is conventionally employed to prevent piracy of software and hardware intellectual property (IP). In this work, we propose a novel application of key-based circuit structure and functionality obfuscation to achieve protection against hardware Trojans triggered by rare internal circuit conditions. The proposed obfuscation scheme is based on judicious modification of the state transition function, which creates two distinct functional modes: normal and obfuscated. A circuit transitions from the obfuscated to the normal mode only upon application of a specific input sequence, which defines the key. We show that it provides security against Trojan attacks in two ways: (1) it makes some inserted Trojans benign, i.e. they become effective only in the obfuscated mode; and (2) it prevents an adversary from exploiting the true rare events in a circuit to insert hard-to-detect Trojans. The proposed design methodology can thus achieve simultaneous protection from hardware Trojans and hardware IP piracy. Besides protecting ICs against Trojan attacks in foundry, we show that it can also protect against malicious modifications by untrusted computer-aided design (CAD) tools in both SoC and FPGA design flows. Simulation results for a set of benchmark circuits show that the scheme is capable of achieving high levels of security against Trojan attacks at modest area, power and delay overhead.     

Reinforcing effect of nanosilica on the properties of natural rubber/reclaimed ground rubber tire vulcanizates

In this investigation, incorporation of silica into natural rubber (NR)‐reclaim rubber (RR) blend system was carried out by sol‐gel technique at various sol‐gel reaction temperatures. The effect of RR on silica reinforcement, hitherto unexplored, was studied for different NR/RR blend systems. The degree of reinforcement of sol‐gel vulcanizates by equilibrium swelling method indicates that the reinforcing efficiency of the in situ generated silica by sol‐gel technique increases with increasing reclaim rubber content. The reinforcing efficiency, tensile properties and thermal stability of sol gel vulcanizates (SGV) prepared at 50°C become maxima as compared to SGV prepared at 30°C and 70°C. The amount of silica incorporated by sol‐gel technique was determined by thermogravimetry analysis. It indicates that the thermal stability increases with silica content. Attenuated total reflection study indicates that RR forms bond with silica particles due to the presence of active functional site on RR. Scanning electron microscopy studies further indicate the coherency and homogeneity in the silica filled NR/RR vulcanizates. The microwave diagnosis of different SGVs was also carried out and the frequency dependence of dielectric permittivity (E') and loss (E”) were measured. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

Efficient testing of SRAM with optimized march sequences and a novel DFT technique for emerging failures due to process variations

With increasing inter-die and intra-die parameter variations in sub-100-nm process technologies, new failure mechanisms are emerging in CMOS circuits. These failures lead to reduction in reliability of circuits, especially the area-constrained SRAM cells. In this paper, we have analyzed the emerging failure mechanisms in SRAM caches due to transistor V/sub t/ variations, which results from process variations. Also we have proposed solutions to detect those failures efficiently. In particular, in this work, SRAM failure mechanisms under transistor V/sub t/ variations are mapped to logic fault models. March test sequences have been optimized to address the emerging failure mechanisms with minimal overhead on test time. Moreover, we have proposed a design for test circuit to complement the March test sequence for at-speed testing of SRAMs. The proposed technique, referred as double sensing, can be used to test the stability of SRAM cells during read operations. Using the proposed March test sequence along with the double sensing technique, a test time reduction of 29% is achieved, compared to the existing test techniques with the same fault coverage. We have also demonstrated that double sensing can be used during SRAM normal operation for online detection and correction of any number of random read faults.     

Silicon Migration from High‐barrier Coated Multilayer Polymeric Films to Selected Food Simulants after Microwave Processing Treatments

The use of microwave (MW) technology for in‐package food sterilization and pasteurization has the potential for widespread use in the food industry. Because the use of MW technology requires that food be processed inside its packaging, the interaction between food and its packaging during processing must be studied to ensure package integrity as well as consumer safety. In this study, two commercially available multilayer films developed for retort sterilization were evaluated for their suitability to MW processing. Film A was composed of oriented nylon//coated polyethylene terephthalate//cast polypropylene (CPP); film B consisted of oriented nylon//coated nylon//CPP with overall oxygen transmission rates <0.2 cc/m². day. Silicon (Si) was a major component in the coated polyethylene terephthalate layer and food‐contact CPP layer. This study evaluated the influence of MW processing on Si migration from films into selected food‐simulating liquids (FSLs; water and 3% acetic acid) using inductively coupled plasma‐mass spectroscopy, as compared with conventional thermal processing. This study also assessed migration of Si into FSL in terms of process temperature (70–123 °C) and time (18–34 min). A Fourier transform infrared spectrometer was used to evaluate the stability of the silicon–oxygen (Si–O) bonds in the metal‐oxide coated and food‐contact layer of the packaging film. Overall, there were no significant differences (p > 0.05) between the level of Si migration from films to FSL and the stability of Si–O–Si bonds during MW processing as compared with the conventional thermal processing. However, we found that the final processing temperature and time had a significant (p < 0.05) impact on Si migration into the FSL. Copyright © 2013 John Wiley & Sons, Ltd.     

Structural, dielectric and electrical properties of ACu3Ti4O12 (A = Ca, Sr and Ba)

Polycrystalline compounds of a general formula ACu₃Ti₄O₁₂ (A = Ca, Sr, Ba) were synthesized by a high-temperature solid-state reaction technique. Crystal structure of the compounds at room temperature studied by an X-ray diffraction (XRD) technique was found to be cubic. Detailed studies of dielectric constant () and loss tangent (tan ) of the compounds as a function of frequency (100 Hz to 1 MHz) and temperature (125 K to 600 K) did not show any ferroelectric phase transition. The ac and dc conductivity studied over a wide range of temperature provided activation energy of the compounds. Variable range phonon-assisted quantum mechanical tunneling technique of correlated barrier hopping (CBH) model has been applied to interpret the temperature and frequency dependent ac conductivity. Using these theoretical models, various model parameters have also been calculated. The temperature variation of resistivity shows that the compounds have negative temperature coefficient of resistance (NTCR).     

Characterization of budding twigs of flower-type zinc oxide nanocrystals for the fabrication and study of nano-ZnO/p-Si heterojunction UV light photodiode

Journal of Materials Science: Materials in Electronics - In this work, we focused on the study of the structural and optical properties of chemical precipitation-derived special shape (budding...