Detection of Hidden Explosives

Detection of explosives is of major importance in several applications related to homeland security, such as detecting hidden explosives in airport luggage, in vehicles and in mail and screening of personnel for concealed explosives. 

The main performance requirements of an explosive detection system are sensitivity, selectivity and speed of analysis. The mass spectrometer meets these requirements. Additional requirements are mobility and cost. During the last years, mass spectrometers have become smaller and mobile, but the prices are stiU relatively high. However, despite the complexity of the mass spectrometer, its performance as an explosives detector is more reliable than most existing vapor and trace detectors. 

Mass spectrometry, and especially LC/MS, is a major technique in the analysis of explosives. It combines good sensitivity and selectivity, and in addition to MS/ MS, provides an excellent identification tool for the forensic analyst. 

Mass spectrometry has not been accepted as a universal technology for the detection of hidden explosives. However, it has been used in the MS/MS configuration in some specific applications for the detection of hidden explosives. 

Objects H/N C/N O/N Actual Tsvc Class Class Psvc Tf Pf KNN Class Class Class Class  

The meaning of Tsvc class and Psvc class are the class assigned by SVC in training and prediction respectively, Tp and Pp are the class assigned by Fisher method in training and prediction respectively, KNN class is the class assigned by KNN method. 

Since the prediction ability of support vector machine is dependent on the selection of kernels and the parameter C. The rate of correctness of computerized prediction tested by LOO cross-validation method has been used as the criterion of the optimization of method of SVC computation. Four kinds of kernels (linear kernel, polynomial kernel of second degree, Gaussian kernel and sigmoid kernel functions) with 10 C 200 are used to test for the best combination of kernel function 

By using linear kernel function and C=100, the criterion to differentiate explosives from ordinary materials is found as follows  

So it can be concluded that support vector machine should be most suitable for the hidden explosive detection. 

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Elemental Analysis, 2) Determination of Pellet Weight in Primers, 3) Determination of Gunpowder Residues in Forensic.Investigations, 4) Detection of Explosives in Buried Mines, 5) Detection of Hidden Explosives in Baggage, and 6) Explosives Safety in Neutron Activation Analysis... 

Mass spectrometry has become a routine technique for forensic analysis of explosives and one of the technologies used for vapor and trace detection of hidden explosives. 

G. Viesti, S. Pesente, G. Nebbia, M. Lunardon, D. Sudac, K. Nad, S. Blagus and V. Valkovic, Detection of hidden explosives by using tagged neutron beams status and perspectives, Nucl. Instrum. Methods Phys. Res. Sec. B, 241 (1—4) (2005) 748-752. 

Kolia R, The application of analytical methods to the detection of hidden explosives and explosive devices, Angew. Chem., Int. Ed. Engl., 36, 800-811, 1997. 

Dr. Yinon s main activities involve applications of novel analytical techniques for the detection and analysis of hidden explosives. 

Conjugated polymers are good sensing platforms for the detection of vapours of nitroaromatic explosives such as trinitrotoluene (TNT) [31]. Fluorescence quenching occurs due to electron transfer from the conjugated polymer to the nitroaromatic species. Common classes of CPs used in nitroaromatics sensing are poly(acetylenes), poly(p-phenylenevinylenes), poly(p-phenyleneethynylenes) and polysilanes. CP sensor platforms have been successfully deployed outside the laboratory for the detection of hidden landmines, where impressive femtogram detection limits for TNT were obtained [32]. 

The lack of a capability to screen for explosives hidden on an individual is a major vulnerability in aviation and general security. Personal privacy issues and perceived health risks have deterred the use of bulk detectors, such as X ray, X-ray backscatter, and millimeter wave, for screening of individuals for concealed explosives. Consequently, the TSA is focused on trace detection as the best solution for passenger screening in airports. The TSA has determined that individuals carrying as little as 1 lb of concealed explosives get sufficiently contaminated to be detectable by portal devices that use trace detectors. The level of contamination on an individual s exterior clothing that can be routinely detected by the best portal devices is about 1 pg or about 1 part in 109 of the explosive mass. 

Shaw, Determining the Potential of Radiofrequency Resonance Absorption Detection of Explosives Hidden in Airline Baggage , SWR1-15-4226-F (1975), (AD A022 111 /9ST) 58) P. 

G. Nebbia and G. Juergen, Detection of buried landmines and hidden explosives using neutron, X-ray and gamma-ray probes, Europhysics News, July/August, no. 4, pp. 119-123 (2005). 

Explosives may reside on a person in the form of trace (residue from handling explosives, exposure to explosives, or hidden explosives) and/or bulk (a large mass of explosives). The portal technologies that enable the detection of these two forms of explosives may be categorized as trace and anomaly. The detection methods utilized by these two types of portals are substantially different in the signature of the material detected and the... 

Gamma-ray spectrometry is a probe of nudear rather than chemical processes, but its high specificity and sensitivity have applications in analysis of materials (286). It is especially suited for activation analysis. Unstable nudides produced by nudear bombardment can be identified by their characteristic gamma-ray decay emissions. An important example is slow neutron capture by nitrogen with subsequent decay of 15 detected from its 1.7—10.8 MeV gamma lines, a signature useful for remote, nondestmctive detection of possible hidden explosives (see Explosives and propet. t.ents). Gamma-ray... 

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