Ground penetrating radar (GPR) is an ultra-wideband electromagnetic sensor used not only for subsurface sensing but also for the detection of objects which may be hidden behind a wall or inserted within the wall. Such applications of the GPR technology are used in both military and civilian operations such as mine or IED (improvised explosive device) detection, rescue missions after earthquakes and investigation of archeological sites. Detection of concealed objects with low metal content is known to be a challenging problem in general. Use of A-scan, B-scan and C-scan GPR data in combination provides valuable information for target recognition in such applications. In this paper, we study the problem of target detection for potentially explosive objects embedded inside a wall. GPR data is numerically simulated by using an FDTD-based numerical computation tool when dielectric targets and targets with low metal content are inserted into different types of walls. A small size plastic bottle filled with trinitrotoluene (TNT) is used as the target with and without a metal fuse in it. The targets are buried into two different types of wall; a homogeneous brick wall and an inhomogeneous wall constructed by bricks having periodically located air holes in it. Effects of using an inhomogeneous wall structure with internal boundaries are investigated as a challenging scenario, paying special attention to preprocessing.
The optical analogue to electromagnetically induced transparency (EIT) is modeled for two separate systems with the same formalism and the spectral characteristics together with the generated group delay are compared. First system is a coherently coupled high-Q multi-cavity array which represents the classical EIT and is limited by the finite broadening of the cavity and the second one is a single embedded quantum dot (QD) cavity system, a cavity-QD EIT, that depends on both QD broadening and cavity properties. Similar spectral characters have been observed for both systems but the former generated theoretically two times higher group delays.
KEYWORDS: Land mines, Target detection, Ground penetrating radar, General packet radio service, Signal detection, Reflection, Defense and security, Metals, Defense technologies, Explosives
There is an increasing demand for noninvasive real-time detection and classification of buried objects in various civil
and military applications. The problem of detection and annihilation of landmines is particularly important due to strong
safety concerns. The requirement for a fast real-time decision process is as important as the requirements for high
detection rates and low false alarm rates. In this paper, we introduce and demonstrate a computationally simple, timeefficient,
energy-based preprocessing approach that can be used in ground penetrating radar (GPR) applications to
eliminate reflections from the air-ground boundary and to locate the buried objects, simultaneously, at one easy step. The
instantaneous power signals, the total energy values and the cumulative energy curves are extracted from the A-scan
GPR data. The cumulative energy curves, in particular, are shown to be useful to detect the presence and location of
buried objects in a fast and simple way while preserving the spectral content of the original A-scan data for further steps
of physics-based target classification. The proposed method is demonstrated using the GPR data collected at the facilities
of IPA Defense, Ankara at outdoor test lanes. Cylindrically shaped plastic containers were buried in fine-medium sand to
simulate buried landmines. These plastic containers were half-filled by ammonium nitrate including metal pins. Results
of this pilot study are demonstrated to be highly promising to motivate further research for the use of energy-based
preprocessing features in landmine detection problem.
The design of aperture shape is a promising approach for enhanced transmission through a subwavelength aperture. We designed split-ring-resonator (SRR)-shaped apertures in order to increase the transmission through subwavelength apertures by making use of the strong localization of the electromagnetic field in SRR-shaped apertures. We obtained a promising result of 104-fold enhancement by utilizing SRR-shaped apertures. It is possible to use these proposed structures at optical frequencies by making several modifications such as decreasing the sharpness of edges and increasing the gap width. Since SRRs are already being realized at optical frequencies, our proposed SRR-shaped aperture structures are promising candidates for novel applications.
An integrated-optic biosensor monitors the concentration of liquid pollutants on the surface of a planar substrate composing single-mode channel waveguides. The concept uses a Mach- Zehnder interferometer structure to measure thickness and/or refractive index changes on the waveguide surface. These changes occur as pollutant molecules interact directly with the interferometer's active arm or with a hydrophobic coating on the surface of the arm. Interferometer output data were obtained for various solutions including PPM levels of benzene and toluene in water. Theoretical analysis indicated that a hydrophobic coating on the waveguide would provide sensor specificity and detect pollutants at PPB levels.
A distributed fiber optic temperature sensing system was developed which
consisted of a high-resolution optical time domain reflectometer (OTOR) and a
special optical fiber sensor. Several 1 kilometer lengths of prototype
sensing fibers were formed by coating a modified, ultraviolet light curable
polymer cladding material onto a core glass during fiber production. By
monitoring changes in Rayleigh backscattered light from the fiber; local
temperature changes were measured along the fiber length. A demonstration
system was assembled with a 20 meter sensing fiber and extensive data were
collected. These measurements indicated that hot spots as small as 10 cm
could be detected over a temperature range of 0 to 150°C with a measurement
accuracy of ±°C
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