Spectro-thermal decomposition study of 1,4-dinitroglycoluril (DINGU)

Simultaneous thermal analysis and high temperature FTIR study of 1,4-dinitroglycoluril (DINGU) is reported. TG showed 90% weight loss in the temperature range 225-250 degrees C. Isothermal TG of DINGU showed about 70% weight loss in the temperature range 210-230 degrees C. Kinetic parameters evaluated using a computer program showed that alpha-t data are best described by the Avrami-Erofeev's equation for n=2 with an activation energy of 165 kJ/mol. The kinetics of decomposition of DINGU was followed by studying NH (3388 cm(-1)), CO (1770-1810 cm(-1)) and NO2 symmetric stretching (1565-1570 cm(-1)) IR bands. All three bands showed loss of intensity with temperature and time. alpha-t data of decomposition with respect to NO2 stretching was again best described by the Avrami-Erofeev's equation for n=2. Gaseous decomposition products observed in the IR were N2O, NO2, CO2, HCN and NO. PM3 and Hartree-Fock level calculations on various bond lengths, bond angles and dihedral angles were computed to support the analysis of decomposition study using TG and IR. The data showed that CN and NH bonds are much shorter than the NN bonds, indicative of the weaker NN bond and hence, the possibilities of rupture of the same bond preferentially. This paper also discusses the sensitivity and performance properties of DINGU.     

A Facile Sol–Gel Strategy for the Synthesis of Rod‐Shaped Nanocrystalline High‐Surface‐Area Lanthanum Phosphate Powders and Nanocoatings

Synthesis of rod‐shaped nanocrystalline lanthanum phosphate with an average length of 40 nm even after calcination at 400 °C has been realized through a room‐temperature aqueous sol–gel process. The sol is characterized by particle‐size, zeta‐potential, and viscosity measurements. Gelation of the sol is induced by ammonia. The lanthanum phosphate phase‐formation process is followed by thermal, Fourier‐transform IR, and X‐ray diffraction analysis. Transmission electron microscopy shows that the sol and gel particles have a rod‐shaped morphology and comparable particle sizes. Using the Scherrer equation a crystallite size of 11 nm is obtained for the gel powder calcined at 400 °C and Brunauer–Emmett–Teller (BET) nitrogen‐adsorption analysis showed a high specific surface area of 100 m² g^–1. Ammonia temperature‐programmed desorption measurements show that the density of Lewis acid sites is four times higher than ever reported in the case of lanthanum phosphates. The catalytic activity of the above sample is demonstrated by using it as a Lewis‐acid catalyst in an acetal‐formation reaction with a very good yield of 85 %. The sol is used to develop nanocoatings on a glass surface and the morphology of the coatings is investigated using atomic force microscopy and scanning electron microscopy. The microstructure of the coating confirmed the rod‐shaped nature of the sol particles. The coating was uniform with a thickness of about 55 nm.     

Census: fast,scalable and robust data aggregation in MANETs

This paper describes Census, a protocol for data aggregation and statistical counting in MANETs. Census operates by circulating a set of tokens in the network using biased random walks such that each node is visited by at least one token. The protocol is structure-free so as to avoid high messaging overhead for maintaining structure in the presence of node mobility. It biases the random walks of tokens so as to achieve fast cover time; the bias involves short albeit multi-hop gradients that guide the tokens towards hitherto unvisited nodes. Census thus achieves a cover time of O(N) and message overhead of \(O(N\,log(N))\) where N is the number of nodes. Notably, it enjoys scalability and robustness, which we demonstrate via simulations in networks ranging from 100 to 4000 nodes under different network densities and mobility models. We also observe a speedup by a factor of k when k different tokens are used (\(1 \le k \le \sqrt{N}\)).     

Trace detection and discrimination of explosives using electrochemical potentiometric gas sensors

In this article, selective and sensitive detection of trace amounts of pentaerythritol tetranitrate (PETN), 2,4,6-trinitrotoluene (TNT) and cyclotrimethylenetrinitramine (RDX) is demonstrated. The screening system is based on a sampling/concentrator front end and electrochemical potentiometric gas sensors as the detector. Preferential hydrocarbon and nitrogen oxide(s) mixed potential sensors based on lanthanum strontium chromite and Pt electrodes with yttria stabilized zirconia (YSZ) solid electrolyte were used to capture the signature of the explosives. Quantitative measurements based on hydrocarbon and nitrogen oxide sensor responses indicated that the detector sensitivity scaled proportionally with the mass of the explosives (1-3 μg). Moreover, the results showed that PETN, TNT, and RDX samples could be discriminated from each other by calculating the ratio of nitrogen oxides to hydrocarbon integrated area under the peak. Further, the use of front-end technology to collect and concentrate the high explosive (HE) vapors make intrinsically low vapor pressure of the HE less of an obstacle for detection while ensuring higher sensitivity levels. In addition, the ability to use multiple sensors each tuned to basic chemical structures (e.g., nitro, amino, peroxide, and hydrocarbon groups) in HE materials will permit the construction of low-cost detector systems for screening a wide spectrum of explosives with lower false positives than present-day technologies.     

Design of MEMS sensor for the detection of cholera and diarrehea by capacitance modulation

Microsystem Technologies - Cholera is caused by vibriocholera bacteria which were present in water or food. Diarrhea is caused by E. coli bacteria which were present in water or food. Bio-sensors...     

Performance analysis of series: shunt configuration based RF MEMS switch for satellite communication applications

Microsystem Technologies - In this paper the RF-MEMS switch with series–shunt configuration on a single quartz substrate is presented to achieve high isolation than the individual series or...     

Influence of metal salts of 4-(2, 4, 6-trinitroanilino) benzoic acid on the burnining rate of double base propellants

Abstract

Cobalt, Nickel, Copper and Lead salts of 4-(2, 4, 6-trinitroanilino) benzoic acid have been evaluated as ballistic modifiers in double base propellant formulations. Measurements showed considerable increase in burning rate over the control propellant, in presence of salts at all pressures in the range 3.43 – 8.82 MPa. The effect of the lead salt, however, was more pronounced and showed a burning rate increase of 50 – 60%; the lower pressure ranges showing higher burning rate enhancement. The salts decompose exothermically: cobalt salt at 270°C (initiation), nickel salt at 300°C, copper salt at 240°C and lead salt at 260 °C.