25 research outputs found
Weighted near-field focusing in an array-based GPR
No full textThis paper presents a 3-D imaging technique for an ultra-wideband (UWB) ground penetrating radar (GPR) with a single transmit antenna and a linear receive array. The video impulse GPR working in the frequency band of 0.3–3 GHz has been designed in IRCTR for landmine detection, i.e., for a near-field application. Installed on a vehicle it can image in one mechanical scan a strip of 84 cm width due to the length of array aperture. The imaging is done by software means only. The developed imaging technique combines a real aperture focusing in the array plane with a synthetic aperture focusing in the mechanical scan direction. To compensate for parasitic time delays in the array channels, a calibration procedure is also described. Owing to directional properties of transmit antenna, the distribution of signal strength over the array is nonuniform that requires an amplitude correction when focusing the real aperture. The authors analyzed how this affects the footprint of the focused array, its cross-range resolution capability and the image quality of antipersonnel plastic landmines which were buried under different array channels. The analysis bases on experimental data sets acquired in the facilities of IRCTR and TNO-DSS. As a result, the authors propose a weighted array focusing that improves the cross-range resolution and provides proper imaging of typical buried landmines.International Research Centre for Telecommunication and RadarElectrical Engineering, Mathematics and Computer Scienc
Array-Based GPR for Shallow Subsurface Imaging
No full textElectrical Engineering, Mathematics and Computer Scienc
UWB FMCW Radar for Concealed Weapon Detection: RF front-end development
No full textCurrent methods for concealed weapon detection are mainly used at stationary security check-points due to complexity and other serious limitations for real-time outdoor scenarios. A mobile imaging radar is considered as a proper solution for fast screening of people at mass events because of its ability to detect both metal and non-metal weapons through clothes. In this thesis, the design of an RF front-end for an UWB Microwave Imaging Radar based on MIMO 2-D array and multichannel FMCW electronics is presented. Requirements to the design were low power emissions and minimization of data acquisition time, cost and complexity. The UWB technology provides high resolution, while MIMO technique helps reducing the number of required antennas in the 2-D array, without a net degradation of performance. The final RF-scheme was selected based on the availability of commercial off-the-shelves RF-components. The performance of the designed RF front-end was evaluated both via theoretical analysis and simulations in a dedicated software Advanced Design System (ADS, by Agilent). The obtained results in terms of sensitivity, dynamic range, down-range resolution and measurement speed demonstrate that the proposed solution is feasible for through-dress detection of concealed weapons.Microwave Technology and Systems for RadarTelecommunicationsElectrical Engineering, Mathematics and Computer Scienc
3D imaging by fast deconvolution algorithm in short-range UWB radar for concealed weapon detection
No full textA fast imaging algorithm for real-time use in short-range (ultra-wideband) radar with synthetic or real-array aperture is proposed. The reflected field is presented here as a convolution of the target reflectivity and point spread function (PSF) of the imaging system. To obtain a focused 3D image, the proposed algorithm deconvolves the PSF out from the acquired data volume with high speed due to fast Fourier transform and implementation in frequency-wavenumber domain. Then the result is tested against two numerical criteria for efficiency, namely error and instability, whose optimal values can be obtained iteratively. Since the PSF differs with distance, the algorithm suits mainly applications with relatively small objects such as concealed weapon detection. Using several PSFs allows us to image a certain range of interest by their successive deconvolution from the same data. Performance of the algorithm has been evaluated experimentally and compared with that of Kirchhoff migration. Measurements were carried out by a 5–25 GHz synthetic aperture radar in the lab, and scenarios included a gun and a ceramic knife in free space, on a large metal plate, and a gun concealed on a dummy under a thick raincoat. The results demonstrate sufficient image quality obtained in a fraction of time.Electrical Engineering, Mathematics and Computer Scienc
GPR antipersonnel mine detection: improved deconvolution and time-frequency feature extraction
No full text
Indirect Speech Acts in the Speech of the Characters of the Tale of Bygone Years
No full textThe article states that communication in Old Russian as well as in modern Russian discourse is characterized by the use of mono-functional and poly-functional indirect speech acts. Moreover, the important aspect that helps to specify the illocutive functions of indirect speech acts in Old Russian is their verifiability: the verbal or non-verbal response of the interlocutor as well as the frame constructions, which introduce direct speech (preposition). These constructions are also used in the middle of the utterance (interposition) or at the end of the utterance (postposition). The author of the chronicles observes the communicative purposes of both the speaker and the interlocutor, indicating that the given utterance should be regarded as an indirect speech act. By analyzing the use of mono-functional indirect speech acts in the original dialogue fragments of the Tale of Bygone Years, the author works out their typology. The groups of interrogative and non-interrogative indirect speech acts have been singled out, each of them having certain typical characteristics. The semantics of non-interrogative utterances in most cases is connected with the expression of indirect meanings of time and aspect of verbal forms. The use of interrogative utterances as indirect speech acts is mostly connected with the changes not only in the illocutive function, but also in the propositional meaning of the predicative unit: interrogative utterances with negations should be interpreted as affirmative non-interrogative utterances and vice versa. The author comes to the conclusion that the use of modern mono-functional indirect speech acts is traditional, since it is identical to their functioning in Old Russian
Global Fukaya category I
No full textLet denote the Frechet Lie group of Hamiltonian
symplectomorphisms of a monotone symplectic manifold . Let be the -nerve of the Fukaya category , and let denote the component of the ``space of -categories'' .
Using Floer-Fukaya theory for a monotone we construct a natural
up to homotopy classifying map \begin{equation*}
BHam (M, \omega) \to (|\mathbb{S}|, NFuk (M, \omega)). \end{equation*} This
verifies one sense of a conjecture of Teleman on existence of action of on the Fukaya category of . This construction is very
closely related to the theory of the Seidel homomorphism and the quantum
characteristic classes of the author, and this map is intended to be the
deepest expression of their underlying geometric theory. In part II the above
map is shown to be nontrivial by an explicit calculation. In particular, we
arrive at a new non-trivial ``quantum'' invariant of any smooth manifold, which
motives the statement of a kind of ``quantum'' Novikov conjecture.Comment: To appear in IMRN, 61 page
