Belgrade, Serbia
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Torki A.M.,University of Belgrade | Zivkovi I.,Institute of Security | Radmilovic V.R.,University of California at Berkeley | Stojanovic D.B.,University of Belgrade | And 3 more authors.
International Journal of Modern Physics B | Year: 2010

This work reports the preparation of SiO2 and TiO 2/poly (vinyl butyral) nanocomposites with enhanced dynamic mechanical properties. Silica and titania nanoparticles were introduced in the matrix as the neat powder and as colloidal sol using the melt mixing process. Composites reinforced with colloidal sol silica and titania showed higher mechanical properties than the ones reinforced with as-received particles. When sol TiO2 particles are used, the highest increase of storage modulus of about 54% is obtained for 5 wt% loading, while for sol SiO2, the storage modulus increases with the addition of nanosilica with the largest increase of about 99% for 7 wt% loading. In addition, nanocomposites were introduced within Kevlar/PVB composites. The addition of 5 wt% silica and titania colloidal sol lead to the remarkable increase of the storage modulus for about 98 and 65%, respectively. Largest contribution of nanoreinforcements in lowering the glass transition temperature is observed for 7 wt% loading of TiO2 and SiO2 colloidal sol. © 2010 World Scientific Publishing Company.

Ilic N.,Institute of Security | Marinkovic A.,University of Belgrade | Mijin D.,University of Belgrade | Nevescanin M.,Institute of Security | Petrovic S.,University of Belgrade
Chemical Industry and Chemical Engineering Quarterly | Year: 2010

The electron-ionization induced mass spectra of twenty six N-monosubstituted cyanoacetamides were recorded and their fragmentation patterns were studied. The effect of N-alkyl and N-aryl substituents to the fragmentation of the investigated compounds was discussed. Mechanistic generalization lead to a conclusion that fission of the carbon-carbon bonds next to carbonyl function or nitrogen were processes common for N-alkyl and N-(4-substituted phenyl) cyanoacetamides. In some amides, the elimination of the acyl group by a ketene fragment gave rise to the more stable ion. Cycloalkyl amides could not fragment by single carbon-carbon bond fission, but subsequent rearrangement resulted in formation of stable even electron ion. N-(4-substituted phenyl) cyanoacetamides were more stable showing also characteristic fragmentation depending on substituent present at phenyl ring.

Nevescanin M.M.,Institute of Security | Avramov Ivic M.L.,University of Belgrade | Petrovic S.D.,University of Belgrade | Mijin D.Z.,University of Belgrade | And 2 more authors.
Journal of the Serbian Chemical Society | Year: 2013

The catalytic abilities of a gold electrode were tested for the quantitative determination of amphetamine (A) and 3,4-methylenedioxy-N- methylamphetamine (MDMA) standards by their oxidation using cyclic voltammetry (CV). The values of the oxidative currents of A and MDMA standards at 0.80 V vs. SCE in 0.05 M NaHCO3 at a scan rate of 50 mV s-1 were linear functions of the concentration in range of 110.9-258.9 -M and 38.7-229.2 -M, respectively. Square wave voltammetry (SWV) revealed a linear increase of current with the concentration of MDMA (range 30.9-91.6 -M), which enabled the quantitative determination of amphetamine derivates. SWV analysis was also successfully performed in spiked urine samples. A and MDMA in the presence of sucrose and as a content in illegally produced tablets were also determined. The voltammetric determinations of A and MDMA derivatives using CV and SWV at gold a electrode are rapid, selective and simple procedures and their accuracy was confirmed with a reference method, high performance liquid chromatography (HPLC). The analysis of spiked urine samples offers an additional possibility for the rapid detection of A and MDMA in human urine. Copyright ©2013 SCS.

Qazanfari K.,University of Tehran | Mirpouryan M.S.,Institute of Security | Gharaee H.,Institute of Security
2012 6th International Symposium on Telecommunications, IST 2012 | Year: 2012

Existing misuse-based intrusion detection methods are often not sufficient in detecting zero-days attacks. As a result, anomaly or learning based intrusion detection mechanisms have been developed to cope with such attacks. Among variety of anomaly detection approaches, Support Vector Machine (SVM) and Multi Layer Perceptron (MLP) are known to be two of the best machine learning algorithms to classify normal from abnormal behaviors. In this paper a hybrid anomaly-based intrusion detection method is proposed that is based on these two methods. These methods are trained in supervised way. We use the following additional techniques to improve the performance of proposed approach: First, a feature selection technique using the entropy of features is used for extracting optimized information from KDD data set and second, a novel method is proposed to combine the results of these two learning based methods. Lastly, we demonstrate the effectiveness of proposed hybrid approach by using the KDD dataset. The simulation results show that which features of KDD are better to distinguish the normal from abnormal traffics. Also these results show the detection precision of the DoS, Probe, U2R and R2L attacks by using our method are 99%, 100%, 100% and 100% respectively. © 2012 IEEE.

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