An oil well produces a mixture of oil, water, and gas in proportions that vary over the lifetime of the well. For the control of the well and the allocation of the production it is important to be able to measure the composition of the flow and the flow rates at various stages in the process. Roxar has a line of products for these purposes. The meters are based on microwave sensors with a varying number of additional sensors, like a radioactive density sensor, a temperature sensor, and a pressure sensor. The paper describes the basic measurement principles, the acquired field experience, and the latest developments of the MFI WaterCut meter and the MFI MultiPhase Meter. A new meter that is being developed for the purpose of measuring the composition of the produced fluid inside an oil well is also described.

The most commonly used nondestructive techniques for materials evaluation are ultrasonics, X and (gamma) -rays, infrared and eddy currents methods. In recent years, considerable efforts have been made in applying microwave techniques to test dielectric materials and metals. Therefore, for a few applications microwave methods can be considered alterative approaches to those conventional means. In this paper we consider the microwave near-field determination of the reflection coefficient of dielectric materials and metals, with varying size of flaws, for nondestructive testing purposes. These measurements and simulations are conducted at 35 GHz. We try to demonstrate that microwaves have their place as one tool in the toolbox of the practitioners.

Corrosion of steel rebar in reinforced concrete structures, can be induced by the presence of chloride in the structure. Corrosion of steel rebar is a problematic issue in the construction industry as it compromises the strength and integrity of the structure. Although techniques exist for chloride detection and its migration into a structure, they are destructive, time consuming and cannot be used for the interrogation of large surfaces. In this investigation three different portland cement types; namely, ASTM types II, III and V were used, and six cubic (8' X 8' X 8') mortar specimens were produced all with water-to-cement (w/c) ratio of 0.6 and sand-to-cement (s/c) ratio of 1.5. Tap water was used when producing three of these specimens (one of each cement type). For the other three specimens calcium chloride was added to the mixing tap water resulting in a salinity of 2.5%. These specimens were placed in a hydration room for one day and thereafter left it the room temperature with low humidity. The reflection properties of these specimens, using an open-ended rectangular waveguide probe, were monitored daily at 3 GHz (S-band) and 10 GHz (X-band). The results show the influence of cement type on the reflection coefficient as well as the influence of chloride on the curing process and setting time.

Measured Radar Cross Section results obtained in an indoor static measurement facility are presented for various wing configurations. The study serves to characterize the internal scattering from electromagnetic transparent wings. The effect of various parameters e.g. spars, ribs, etc. on the scattering contribution from the wing will be demonstrated using spheres with flat plates to simulate the internal contributors to the backscattered field.

This paper reviews the various applications of microstrip antennas with special emphasis on subsurface sensing, microwave moisture measurement and nondestructive testing of dielectric materials. With reference to the literature, we first describe the commonly used GPR-antennas, the printed Vivaldi-antennas, and microstrip antennas used in moisture content measurement. Furthermore, attention is given to the problems of new antenna technologies, showing examples for active integrated antennas, a photonic band gap patch antenna and a silicon micromachined patch antenna. The reminder of the paper summarizes relevant R&D activities in microstrip antennas at BUTE/DMT, focusing on near-field experiments, monitoring of particleboards and WLAN- applications of patch radiators.

Significant progress has been made in recent years in the development of microwave tomographic systems for medical applications. This technique has also similar potential for industrial applications. It can be used as an alternative to (chi) -ray, magnetic resonance, and ultrasound imaging systems, providing good images at a lower cost. This paper presents an appropriate microwave tomographic scanner designed for industrial applications. The microwave antennas and the object are not immersed in water, unlike those developed for medical imaging. The aim is to image an object with the antennas suspended in free space. We have implemented a system using sixteen monopole transmitting and sixteen monopole reception antennas surrounding an object of a maximum diameter of 12 cm, and Newton Kantorovich image reconstruction algorithm. The images of dielectric objects from the experimental data of scattered fields measured around such objects are reconstructed and presented.

During the calibration of dielectric moisture measurement methods the complex value of permittivity will be assigned to the moisture content determined by the oven dry method. The measured complex value of permittivity will be influenced by the moisture content, by density variations, and salt content. In the microwave range different methods exist to increase the accuracy of moisture measurement in production processes and at the analysis of structural conditions. The most promising methods to reduce the influence of the density use a multi-parameter-measurement at one or more frequencies in the range of radio frequencies or microwaves. This trend is a result of developing opportunities in instrumentation design and production of numerous microwave components and fast computer equipment.

Using microstrip line for determining moisture content in a broad range for samples of sawdust is described in this paper. The determination was based on the measurements of the attenuation and phase shift of an electromagnetic wave transmitted through a layer of wet material that is placed onto the microstrip line. The measurements were made at two frequencies (6 GHz and 9 GHz) on sawdust samples of varying dry densities (0.13 - 0.20 g/cm³) at room temperature. The changes of attenuation and phase shift at the two frequencies were used to obtain the density-independent calibration equation. Experimental results for sawdust in moisture range of 10 to 190% on dry basis are presented. The average error in moisture content determination was 4.65%.

Subsurface sensing often implies the intention to look deep into the hidden structures. A special task is the analysis of the `skin' itself, which covers the deep structures and builds the surface layer which can not or may not be penetrated. There are also many cases where thin material layers are embedded in another materials and can be measured only from one side, from the outside. The object of the investigations are often the quality, the moisture content or hydraulic conductivity of this `skin'.

After introducing some possibilities and related problems of microwave moisture measurements, a non-destructive testing method of large-sized dielectric boards is shown, which is based on a microwave free-space/double transmission/reflection type two-parameter complex vector measurement. Unlike this basic idea, a 5.8 GHz monitoring system was developed, which is used for moisture content measurement and quality forecast of particleboards continuously, before mechanical testing would be accomplished. Recalling some basic equations, the calculation of Kasa's circles, dry wood basic weight, complex permittivity values, absolute moisture content and mechanical properties of composite boards, also are shown. Low cost MMICs, self-designed microstrip antennas and passive detector/backscatters are used in the instrumentation for the realization of the concept.

Microwave control capabilities have been used to monitor the degradation of polyol, an alcohol composite material commonly used in the footwear industry for polymerization purposes. The liquid flows continuously inside a thin pipe and its desirable properties are altered with time associated to moisture absorption processes. Consequently, variations in the dielectric properties are involved, and they can be detected by permittivity measurements. In this paper, in order to obtain high sensitivity and resolution, a rectangular cavity resonator working at a fixed frequency was designed using as sample holder a rectangular pipe containing the liquid going through. Changes in the liquid modify the original response of the cavity with a non- degraded liquid and these differences have been used to determine the degree of degradation of the material. The final response of the microwave resonator was experimentally validated with measurements in a continuous line.

Northeastern University is heading one of three teams involved in five year, 5,000,000 dollar Multidisciplinary University Research Initiative programs in demining, supported by the Army Research Office. The Northeastern effort involves a team of six other universities and small businesses and integrates electromagnetic, acoustic, and optical sensing modalities. We are designing sensors to measure many of the physical characteristics of the ground with and without mines, and developing carefully-tailored signal processing algorithms that specifically take the sensor and the physics into account.

This paper reviews the problem of subsurface discrimination using electromagnetic induction sensors. Typically, discrimination is based on differences in the multiaxis magnetic polarizability between different objects. We review work on frequency and time domain systems, and their interrelationship. We present the results of comprehensive measurements of the multiaxis electromagnetic induction response of a variety of inert ordnance items, ordnance fragments and scrap metal pieces recovered from firing ranges. The extent to which the distributions of the eigenvalues of magnetic polarizability for the different classes of objects do not overlap establishes an upper bound on discrimination. For various reasons, the eigenvalues cannot always be accurately determined using data collected above a buried target. This tends to increase the overlap of the distributions, and hence degrade discrimination performance.

Although commercially available geophysical sensors are capable of detecting UXO at nominal burial depths, they cannot reliably discriminate between UXO and clutter. As a result, an estimated 75% of remediation funds are spent on nonproductive excavations. During the past few years, we have been studying the merits of using multifrequency EMI data for discriminating between UXO and non-UXO targets and believe the method has tremendous potential. The EMI spectral response of an object is a function of its electrical conductivity, magnetic permeability, shape, size, and orientation relative the primary exciting field. By measuring a target's spectral response, we obtain its characteristic frequency-dependent signature.

A phased geophysical study of ordnance detection and discrimination specific to the Fort Ord, California environment is currently underway. The purposes of this study are to evaluate existing state-of-the-art OE detection instruments and systems and the ability of these devices to discriminate potential OE items from OE scrap and non-OE scrap in the specific OE, geologic, and cultural environments in and around Fort Ord.

This paper presents recent advances and case histories of two non-traditional electromagnetic geophysical techniques for oil reservoir characterization, and production/process monitoring. The crosswell electromagnetic induction method has seen rapid advancement since its inception in the early 1990's, and to this date numerous surveys have been completed in active oil fields as well as other sites. Here one example is given where a 2D electrical conductivity image derived from crosswell data is employed for reservoir characterization, and two other examples presented where the method provided valuable insight into the 2- and 3-D progress of water flood operations. The second, less mature method discussed involves 3-D imaging from multi-component induction log data. Here all three components of the magnetic field generated by a single or multiple sources are inverted to produce estimates of the electrical conductivity distribution surrounding the borehole. For this technology an example is given of three component data acquisition in an active oil field, as well as a proof of the 3-D imaging concept on a synthetic data set.

We propose the hybridization of the extended Born approximation (EBA) with the conjugate-gradient fast Fourier Hankel transform (CG-FFHT) method to improve the efficiency of numerical solution of borehole induction problems in axisymmetric media. First, we use the FFHT to accelerate the EBA as a nonlinear approximation to induction problems, resulting in an algorithm with O(N log₂ N) arithmetic operations, where N is the number of unknowns in the problem. This improved EBA is accurate for most formations encountered. Then, for formations with extremely high contrasts, we utilize this improved EBA as a partial preconditioner in the CG-FFHT method to solve the problem accurately with few iterations. The seamless combination of these two approaches provides an automatic way toward the efficient and accurate modeling of induction measurements in axisymmetric media.

Incorporation of independent formation information into inductive log interpretation will become more important as the resolution demands on induction logging increase. Often, such information can consist of a reasoned petrophysical characterization of the target and its inductive signature. This target characterization, together with other information, can be used to adaptively focus array tools as a function of borehole depth.

The predicting and monitoring of fluid movement during a steam-injection operation is much important in an EOR process. A crosswell 2D conductivity imaging technique is developed to monitor the injection or production profiles by inverting formation conductivity from crosswell electromagnetic measurements. The tool responses are calculated from electromagnetic field equations using perturbation approach. Maximum entropy constraint is used to regularize the inversion problem. To assure the stability and fast convergence, the inversion procedure is conducted in three steps: homogeneous inversion that assumes the formation with an unique conductivity; 1D inversion that generates horizontally layered formation; and 2D inversion that regards the conductivity anomalies both in vertical and radial directions. An initial guessed value of homogeneous background is needed for the program at the beginning. The calculated result of homogeneous medium is then used as the initial value of 1D inversion, and the reconstructed layered conductivity profiles are the initial input for the 2D inversion. By the steps from homogeneous to heterogeneous inversion, the misfit between measured and calculated data decreases sharply. The examples for both synthetic data and field data are illustrated. The inversion results show that the reconstructed conductivity images are in agreement with the known formation characters within given error tolerances.

Nuclear magnetic resonance (NMR) measurements have become an important part of oilfield well-logging to identify and quantify oil and gas reservoirs. In this paper, some design aspects of NMR sensor for well-logging applications are discussed. The RF and static magnetic fields are computed using a 3D finite element method (FEM). A perturbation technique along with FEM is used to evaluate the power loss in conductors that avoids the need for small discretization steps along the conductor thickness. The magnet is built by stacking several magnet segments along the axial direction and the objective is to magnetize and shape these segments in such a way so as to produce a desired field profile in front of the magnet. An optimal control technique is used in conjunction with the FEM to speed up the design process with signal-to-noise ratio, frequency of operations, depth of investigation, and prepolarization time being the optimization constraints. Very good agreement between the measured and computed antenna efficiency and magnetic field is obtained thus validating the numerical model.

An innovative spectroscopic diagnostic method has been developed for investigation of different regions of normal human skin tissue, as well as cancerous and precancerous conditions in vivo, ex vivo and in vitro. This new method is a combination of fiber-optical evanescent wave Fourier Transform infrared (FEW-FTIR) spectroscopy and fiber optic techniques using low-loss, highly flexible and nontoxic fiber optical sensors. The FEW-FTIR technique is nondestructive and very sensitive to changes of vibrational spectra in the IR region without heating and staining and thus altering the skin tissue. A special software package was developed for the treatment of the spectra. This package includes a database, programs for data preparation and presentation, and neural networks for classification of disease states. An unsupervised neural competitive learning neural network is implemented for skin cancer diagnosis. In this study, we have investigated and classified skin tissue in the range of 1400 to 1800 cm^-1 using these programs. The results of our surface analysis of skin tissue are discussed in terms of molecular structural similarities and differences as well as in terms of different skin states represented by eleven different skin spectra classes.

Early detection of breast cancer is an important part of effective treatment. Microwave detection of breast cancer is of interest due to the contrast in dielectric properties of normal and malignant breast tissues. We are investigating a confocal microwave imaging system that adapts ideas from ground penetrating radar to breast cancer detection. In the proposed system, the patient lies prone with the breast extending through a hole in the examining table and encircled by an array of antennas. The breast is illuminated sequentially by each antenna with an ultrawideband signal, and the returns are recorded at the same antenna. Because the antennas are offset from the breast, the dominant component of the recorded returns is the reflection from the thin layer of breast skin. Two methods of reducing this reflection are compared, namely approximation of the signal with two time shifted, scaled and summed returns from a cylinder of skin, and subtraction of the mean of the set of aligned returns. Both approaches provide effective decrease of the skin signal, allowing for tumor detection.

The aim of the present study is to examine the availability of NIR FT Raman spectroscopy in the clinical evaluation of positive allergic and irritant or doubtful patch test reactions. Instrumental measurements at 42 positive patch test sites in 16 patients were compared visually and evaluated at 48 h and 72 h in order to examine the sensitivity of this method to detect the biochemical changes occurring at the sites of the patches. Raman spectra of normal control skin and skin reacting to patches on the back were obtained with an FRA 106 Raman module on a Bruker IFS 66 optics system (Bruker, Karlsruhe, Germany). The most significant changes in the spectra were detected in the region specific for water content and protein structure in both types of reactions at 48 h and 72 h, compared to normal skin.

Fourier-Transform Infrared Spectroscopy (FTIR) employs a unique approach to optical diagnosis of tissue pathology based on the characteristic molecular vibrational spectra of the tissue. The architectural changes in the cellular and sub-cellular levels developing in abnormal tissue, including a majority of cancer forms, manifest themselves in different optical signatures, which can be detected in infrared spectroscopy. The biological systems we have studied include normal, premalignant (polyp) and malignant human colonic tissues from three patients. Our method is based on microscopic infrared study (FTIR-microscopy) of thin tissue specimens and a direct comparison with normal histopathological analysis, which serves as a `gold' reference. The normal intestine tissue has a stronger absorption than polyp and cancerous types over a wide region in all three cases. The detailed analysis showed that there is a significant decrease in total phosphate and creatine contents for polyp and cancerous tissue types in comparison to the controls.

Optical fibers transparent in the mid-infrared (IR) enable absorption measurements in remote location. New techniques will enhance the possibility using IR fibers for measurements in ATR-mode. If the fiber is in contact with a sample that has characteristic absorption lines, the total transmission of the fiber and sample of these lines will decrease. In this way the absorption of a sample can be determined using a non-destructive method. This work has proven the suitability of flattened IR-Fiber as a tool for detection of organic substances. Initial investigations using bio-organic compounds, bio-liquids, tissue in the native and coagulated state, and micro-organisms have already been carried out with a view to bio-medical usage. An experimental set up was based on an FTIR-spectrometer, fiber optic cables and an external detector. A segment of 1.5 cm at the center of the fiber was flattened to approx. 150 micrometers . Transmission spectra of flattened fibers have been compared to those of the cylindrical fibers. Spectral differences were obtained indicating a possible use for the study of thermal damage in tissues.

Confocal Raman microscopy has recently developed into a routine tool for the depth profiling of polymeric materials, providing microscopic (molecular) level characterization of surfaces and interfaces. A spatial resolution of 1 - 2 micrometers is easily attainable with modern instrumentation. The use of such an instrument is illustrated by describing recent work from the author's laboratory. (1) The distribution and redistribution of small molecules in polymeric materials. (2) The measurement of concentration gradients at a polymer- polymer interface. (3) The probing of a diffusion of a silane primer to a polymer/glass interface. (4) The quantification of the surface selectivity of chemical treatments for modification of polymer surface properties. It is demonstrated that the technique has tremendous potential as a tool for future materials analysis across a broad area.

An advanced infrared interferometric method using fiber optics has been developed for biomedical, environmental and industrial applications. The fiberoptic Evanescent Wave Fourier Transform Infrared (FEW-FTIR) spectroscopy method has been applied to diagnostics of numerous materials including living tissue without sample preparation. This highly sensitive diagnostics tool can conduct surface and subsurface analysis at the molecular level on such diverse materials as human tissue and body fluids, plants, soil, rocks, chemicals, oil, paper and polymers nondestructively, noninvasively in vivo. Operating in the attenuated total reflection regime in the middle-infrared range, the FEW-FTIR technique provides direct contact between the fiber probe and any surface. Our fiber optical spectroscopic device is compact, portable for any application and operates up to a distance of three meters with extremely low loss and nontoxic fibers. This method allows the detection of functional chemical groups and bonds directly from a surface by soft touching of a surface for 15 sec. Applications of this method include (1) early diagnostics of precancerous conditions and other diseases, (2) sun, laser radiation and the influence of other environmental factors (water, pollution and weather), (3) quality control during manufacturing processes, in process analysis.

The purpose of this study is to obtain chemical information from complex materials at different depths, without destroying the structure, by using a FT-Raman fiber-optic probe. This concept combines the flexibility of a fiber- optic probe with depth profiling capabilities similar to those of a confocal microscopy. The fact that the numerical aperture of the probe is lower than in microscope objectives explains the improvement in the range of depth penetration, from micrometers to millimeters, as well as the loss observed in depth resolution. Since the design of the filtered probe is based on confocal optics, it is possible to guide the focus through 6 - 7 mm thick material thereby providing detailed chemical information on different layers at different depths. The confocal properties of the fiber optic probe have been characterized by profiling a 6 micrometer polystyrene film, and comparing the results with those obtained on a FT-Raman microscope. We will present results of molecular depth profiling studies on multi-layer sheets of different polymers, including the determination of chromatic shift, layer thickness and polymer chemistry. Applications on other material depth profiling will also be discussed.

Development of Polycrystalline Infrared (PIR-) fibers extruded from solid solutions of AgCl/AgBr has opened a new horizon of molecular spectroscopy applications in 4 - 18 micron range of spectra. PIR-fiber cables and probes could be coupled with a variety of Fourier Transform Infrared spectrometer and Tunable Diode Lasers (TDL), including pig tailing of Mercury Cadmium Tellurium (MCT) detectors. Using these techniques no sample preparation is necessary for PIR- fiber probes to measure reflection and absorption spectra, in situ, in vivo, in real time and even multiplexed. Such PIR-fiber probes have been used for evanescent absorption spectroscopy of malignant tissue and skin surface diagnostics in-vivo, glucose detection in blood as well as crude oil composition analysis, for organic pollution and nuclear waste monitoring. A review of various PIR-fiber applications in medicine, industry and environment control is presented. The synergy of PIR-fibers flexibility with a super high resolution of TDL spectrometers with (Delta) v equals 10^-4 cm^-1, provides the unique tool for gas analysis, specifically when PIR-fibers are coupled as pigtails with MCT-detectors, and Pb-salt lasers. Design of multichannel PIR-fiber tailed TDL spectrometer could be used as a portable device for multispectral gas analysis at 1 ppb level of detectivity for various applications in medicine and biotechnology.

This work presents the new approach to the investigation of mass transport process in polymers. The Fiber Optic Evanescent Wave Spectroscopy has been used for the real time investigation of diffusion processes in glassy polymers. Unclad AgClBr fibers of 0.9 mm diameter were dip coated by polystyrene layers of 1 - 30 micrometers thickness. The transmission of the fibers in the mid-IR was measured using a Fourier Transform Infrared spectrometer. The penetration of liquids into these layers gave rise to significant changes in the measured spectrum. These changes were used for diffusion studies in situ. The mathematical model, which allows realizing the quantitative treatment of experimental data, was developed. The model details with processes which take place at two interfaces: polymer/liquid and polymer/optical fiber. It was established that the initial stage of diffusion is of the strictly Fickian character. The model permitted us to calculate the coefficient of diffusion of water in polystyrene with a high accuracy. The huge amount of experimental points, which could be obtained by our method, allows calculation of the equilibrium concentration of penetrating liquid with an extremely high precision. This advantage of FEWS procedure offers a high accuracy of calculations of parameters of diffusion. It must be emphasized that the thickness of the film that could be defined with the least precision doesn't affect on final results. The final stage of diffusion is non-Fickian.

Films with various thicknesses were formed from pyrene labeled poly (methyl methacrylate) (PMMA) high T_g latex particles, sterically stabilized by poly isobutylene. Annealing of films were performed above T_g at elevated temperatures up to 270 degree(s)C for 30 min time intervals. UV- Visible technique was used for monitoring of film formation and dissolution. Absorption of chloroform molecules into the annealed latex film was followed by diffusion of PMMA chains into solvent reservoir. Diffusion coefficients of PMMA chains were measured and found to be in between 2.6 x10^{- 9} cm² s^-1 to 9.7 x 10^-13 cm² s^-1 for the latex films in various thicknesses. It was observed that thicker films dissolved much faster than the thinner films.

In this paper, we present a unique approach to wide frequency band high/low temperature dielectric characterization of materials from 8.0 GHz to 110 GHz and the temperature range from -40 to 1500 degree(s)C. Using a HP 8510 XF single connection, single sweep network analyzer along with 3 pairs of spot focused horn lens antennas, it is possible to perform broad band in-situ and real time dielectric characterization of materials. Presently all other methods restrict the measurements either to narrow frequency bands due to sensor/applicator restrictions or difficulties with accurate sample preparation for different frequency bands. This method, based on a microwave beam focused to a measurement plane, is non-contact, so it can be easily adapted for measurements in high temperature and hostile environments. Frequency dependence of the complex dielectric properties of a number of common samples are measured as a function of temperature and frequency, and compared with existing data. This approach can be easily adapted for process monitoring that involves very high or very low temperatures.

A virtually conical cable model of an open-ended coaxial- line probe for converting its measured reflection coefficients into the complex permittivity of a contacted material is presented here. Both reflection coefficients of air and pure water are calculated by employing the FDTD method, and the phase difference between the calculated and the measured reflection coefficients of pure water is used as a calibration factor of the probe. The virtually conical cable model renders the conversion of the complex permittivity of dry sand more accurate and faster than the integral equation model to the aperture admittance.

A digital, multi-frequency EM image system is developed based on the induction principle for subsurface imaging near a sewage pipe. This system, which features a broadband operation, can transmit sinusoidal in a frequency range of 1.25 KHz to 10 KHz. A micro controller is used for all controls and computations for both the transmitter and receiver circuits. Synchronous sampling is used for digitization in order to compute the phase as well as the amplitude of the receiving signal. The system operates in the frequency domain and both the phase and amplitude information can be computed through a DSP algorithm. Test results indicate that the multi-frequency EM sensor is superior in both the missing manhole detection and general subsurface conductivity imaging to the conventional single- frequency sensors. For loop antennas with a spacing of 0.5 m, the system has phase resolution about 1 degree(s) and amplitude resolution about 0.5 percent.

A sensor by definition should be non-intrusive and respond faithfully to the parameter that one is trying to measure. Ideally the sensor should be small so that it does not disturb the field it is trying to measure and permit implementation on new and existing systems without requiring redesign of the system. Power supply to activate the sensor and extract data from the sensor is often the Achilles heel in implementation. Surface Acoustic Wave (SAW) devices also called the IDT Microsensor fit the bill ideally. They are in fact the first MEMS devices made, although this is not generally recognized. Unlike other MEMS devices, a SAW device has no moving parts. SAW devices can be mass-produced using semiconductor fabrication methods. The operation and use of Inter Digital Transducer (IDT) microsensor will be reviewed. Our major interest is that these sensors operate at RF frequencies and can hence be excited wirelessly using microstrip antennas from a remote source. Thus, one can achieve a passive sensor and retrieve the sensor data wirelessly. Whenever sensing is needed on a rapidly rotating system such as helicopter blades or automobile tires, in subsurface situations or inaccessible locations, a wireless passive sensor is the ideal solution. This talk will overview research on design and application of wireless IDT microsensors to dynamical strain monitoring, ice sensing, temperature and humidity sensing, liquid characterization and currently to tire pressure measurements.

This research investigates the effect of leakage induced soil property changes on the attenuation of seismic boundary waves (i.e., Stonely waves) propagating along a liquid- solid-(tank bottom-) soil boundary. An empirical model has been presented for the computation of this attenuation, and its effect has been quantified using numerical examples. The results show small changes (of the order of few percent) in Stonely wave amplitude. The attenuation measurement concept presented here augments the leak detection concept using velocity measurement presented in a previously published paper. Monitoring amplitude loss in conjunction with velocity changes of Stonely waves can result in a more accurate leak detection scheme.

A novel approach is presented for the nondestructive, non- contact and in-situ inspection of curved dielectric objects using a spot focused free space measurement system. The use of a focused antenna permits spot by spot plane wave illumination of approximately one-wavelength diameter spots on a curved body to facilitate near field scanning. Benchmarking measurements were made on curved Plexiglas and glass samples of convex-concave shape with different radii of curvature and the complex permittivities were computed from the measured transmission coefficients. Comparing the results with planar samples show that the curvature does not significantly affect the accuracy of the measured permittivity of cylindrical surfaces if the local radii of curvature are larger than the spot size. Applications of the computer controlled, automated system for characterizing surface resistivity, radome IPD and transmission efficiency as well as potential uses in quality and process control during the manufacture of complex structures will be addressed. Variation in material properties, trapped moisture, manufacturing defects, etc. can be identified and located with precision. The other benefit of this approach is the non-contact nature of the method, which permits measurement of solids and liquids in high/low temperature environments. The spot focused beam permits characterization of small or large samples.

The development of a unified discipline of subsurface sensing and imaging is a key to progress in imaging solutions in the underground, underwater, and bio-medical domains. We present a systems approach to the identification of research thrusts to create and apply this unified framework to solve pressing societal problems in the bio- medical and civil-environmental areas.

This paper addresses the problem of deriving as much as possible information from the measurement at a single antenna position, or spatial point. To this end, an inverse scattering approach retrieving the dielectric permittivity profile as a function of depth from the frequency domain data is presented. The method is capable to locate subsurface objects and distinguish between them depending on their permittivity value compared to the background. The validity and high robustness of the method are demonstrated with the use of synthetic data obtained for layered dielectric media. Experimental verification has been performed in the frequency band of 1 to 4 GHz using vector network analyzer. The influence of operational frequency band on the radar characteristics is discussed.

We present a method to simulate scattering of microwaves in realistic soil representations. Our results will be used by the designers of a new microwave antenna for humanitarian mine clearance being developed within the European Project PICE. We aim to identify scenarios giving false alarm signals and search for means to avoid these conditions. We use the Discrete Dipole Approximation (DDA), a method originally developed to study the scattering of light by particles in interstellar dust. The DDA simulates the scattering objects by a lattice of electric dipoles and calculates the total scattering as the contribution of all the dipoles in the lattice to the total field. It is a very suitable method to study electromagnetic scattering by objects of irregular shape and by clusters of them. We have successfully applied DDA to the analysis of light scattering by clusters of many thousands of particles, simulating pigments in paper coatings.

In this paper a sampling method, based on an irregular and adaptive strategy, is described. It can be used as automatic guide for rovers designed to explore terrestrial and planetary environments. Starting from the hypothesis that a explorative vehicle is equipped with a payload able to acquire measurements of interesting quantities, the method is able to detect objects of interest from measured points and to realize an adaptive sampling, while badly describing the not interesting background.

We invert for the axisymmetric conductivity distribution from borehole electromagnetic induction measurements using a two-step linear inversion method based on a fast Fourier and Hankel transform enhanced extended Born approximation. In this method, the inverse problem is first cast as an under- determined linear least-norm problem for the induced electric current density; from the solution of this induced current density, the unknown conductivity distribution is then obtained by solving an over-determined linear problem using the newly developed, fast Fourier and Hankel transform enhanced extended Born approximation. Numerical results show that this inverse method is applicable to a very high conductivity contrast. It is a natural extension of the original two-step linear inversion method of Torres-Verdin and Habashy to axisymmetric media. In the first step, the CPU time costs O(N²). In the second step, the CPU time costs O(N log₂ N) where N is the number of unknowns. Because of the fast Fourier and Hankel transform algorithm, this inverse method is actually more efficient than the conventional, brute-force first-order Born approximation.

This work concentrates on the analysis of radar signature signals for the characterization and efficient computational of finite discrete 2D point spread functions. A general simple model for ground penetrating raw data image formation is assumed in order to concentrate on the efficient computation of point spread functions. The point spread functions are used as impulse response functions for the simulation of high resolution image of 2D synthetic aperture imaging kernels. A methodology has been developed to serve as a tool aid in the analysis, design, and efficient implementation of 1D and 2D fast Fourier transform (FFT) algorithms prevalent in SAR image formation operations with the idea in mind of reducing the computational effort and improving the hardware implementation process. Kronecker products algebra, a branch of finite dimensional multilinear algebra, has been demonstrated to be a useful tool aid in the development of fast algorithms for unitary transformations and in the identification of similarities and differences among FFT computational frameworks.

The results of theoretical and experimental researches showing the efficiency of synergy of radar and proper radio thermal signals are presented. Microwave methods of radar and radiometer signals joint processing for needs of observed surfaces and media anomalies detection and identification are developed. Developed methods allow to filtrate previously the signatures and the targets related to other classes by their origin.

Advanced technologies, such as coring, geophysical methods, and remote sensing, are successfully applied to subsurface prospecting. In particular, modern electro-optical sensors are sturdy enough to meet the requirements of an archaeological survey. In the framework of the project ARCHEO, funded by the Italian Ministry for Universities and Scientific and Technological Research, we have developed GEOSCOPE, an innovative instrument equipped with miniaturized electro-optical sensors for archaeological prospecting. GEOSCOPE consists of a coring machine and a probe: the coring machine bores the soil while recording the drilling parameters, the probe performs visual inspections and data acquisitions in the hole. A user-friendly computer interface allows the archaeologist to acquire, record, and display measurements and images.

We describe the design and the development of a new prototype to obtain Self-Potential (SP) tomographic images (2D, 3D and 4D) of subsoil. The method of SP is a passive geophysical prospecting method: the data are generally measured on the earth surface as potential drops across a passive dipole, normally consisting of a pair of grounded electrodes, moving along a selected direction. Starting from the measure of the natural electric field along selected profiles and/or maps, we evaluated the probability to identify in subsoil positive and/or negative charge accumulation zones. The prototype has been implemented assembling some hardware components of National Instruments and developing ad hoc a software in C⁺⁺ and VB language. The system allows to measure the SP voltage differences between electrodes regularly distributed along selected profiles and/or maps (maximum 128 channels). In real time the software produces a high resolution tomographic image representing the probability to find electrical sources in subsoil. The main applications of this prototype regard the near surface geophysical exploration in areas characterized by high hydrogeological hazard. In particular the system is able to depict the groundwater circulation system in landslide body, to describe the spatial and temporal dynamics of pollutant diffusion processes in aquifers and to localize seepage phenomena in dam embankment.

Laser remote sensing has proved to be a mature technique in many scientific, military, and civilian fields. In particular, laser range-finders are widely applied in non- contact measurements of distances. In the framework of the project ARCHEO, funded by the Italian Ministry for Universities and Scientific and Technological Research, we have developed GEOLIDAR, a miniaturized laser range-finder that provides useful information for archaeological excavations. More precisely, GEOLIDAR performs volumetric characterizations of underground cavities, such as buried tanks, temples, and tombs. A coring machine bores a small- diameter hole up to the cavity where GEOLIDAR is let down and executes a motor-driven 3D scan. Operation and acquisition are fully controlled by a user-friendly computer interface.

The Florida Department of Transportation and the University of Florida Electronic Communications Laboratory are currently working on a task to fuse the data from ground- coupled and air-launched ground penetrating radar systems. The goal of the project is to improve the overall accuracy of the system and to extract additional information from the data. This paper will describe the methods and signal processing techniques being developed for this project as well as provide examples of processed data that demonstrate applications.

Surface distress is a fairly good indicator of rehabilitation needs but it does not directly relate to remaining life estimates. Mechanistic pavement design requires that strains be calculated utilizing more or less complex modeling. Over the years many devices measuring surface deflections under a given load have been developed. The device by choice for assessing strains due to load is the falling weight deflectometer (FWD). It creates an impulse load on the pavement surface. The data are commonly used in models for backcalculation of elastic moduli and strains. More complex modeling would involve finite element or dynamic element methods. The FWD method has proven to be an excellent tool for overlay design. For this purpose its simplicity and straightforwardness are well documented. However, to successfully backcalculate layer stiffness adequate layer thickness is needed. Thus there is a strong need for assessing layer data at testing points. Using Ground Penetrating Radar (GPR) it is possible to achieve data without coring. The present paper is a part of an ongoing bearing capacity study carried out by a regional road administration in central Sweden. Its objective is to optimize testing for equipment and methods used and presently available. In addition to evaluate the results from the study, the present paper discusses some other applications for GPR that may evolve from it.

In the framework of ARCHEO, a national research project funded by the Italian Ministry for Universities and Scientific and Technological Research, a new ground penetrating radar has been developed by the Italian Consortium for Research on Advanced Remote Sensing Systems. The system has been specially designed to meet archaeological requirements and it will be used to identify and characterize buried finds. The paper summarizes the main guidelines followed during the design phase and presents the radar architecture.

Development of a prototype system has shown that buried explosive compounds, such as those employed in landmines can be detected, located and identified based upon their chemical effluence. A commercially available `soft' x-ray source provides the excitation energy. Excited energy is collected by a `refractive' optic which provides high signal gain to a proprietary germanium crystal sensor/detector. Neural net based discrimination software filters the signal and comparison algorithms define the compounds of interest. The system provides `explosive/no explosive' and explosive compound identification reporting and provides GPS based mapping. The system employs first order data, is forward looking and noncontact. Testing indicates it can be efficacious from an airborne platform.

Holometrics, Inc. has over 12 years in R&D and production of scanning laser radar systems that form the basis for a family of 3D Vision System products. This paper focuses on our on-going activities to field 3D vision systems that can be mounted on small, mobile robots for use in explosive material handling and disposal and/or the inspection of buildings that have been damaged by an earthquake or explosion. In addition, this same configuration can be used in hostage situations in public buildings or in prison riots. The robot/3D vision system configuration is ideal for supporting law and fire officials with the geometric features of a scene as well as quantifying the dimensional and spatial relationships of objects and persons in the scene. The vision system uses an infrared laser to accomplish the scene scanning thus enabling it to operate very effectively in total darkness or daylight. We will describe the technical features of these vision systems and then present a number of 3D images that can be used for the above-mentioned applications.

This paper deals with the application of stepped frequency radar to subsurface imaging of buried targets with a final aim of object imaging and identification. The applications are mainly mines or UXO detection but also buried pipes. The depths considered here are a few cm to 15 cm under the surface (from the top of the object). It is necessary to use a UWB radar in order to separate the soil interface from the top of the object. A versatile system has been built that can be brought outdoor. It is used to find the best parameters for a future optimal radar. Special antennas have been realized that cover the 500 MHz to 8 GHz frequency range. The antenna pair (T/R) moves at a given height over the soil surface along a rail. Radar returns are then processed on a PC in order to deliver in a few seconds a 2D vertical profile of the soil. A special algorithm for near field synthetic focusing aperture has been developed for this task. It takes into account the wave propagation in the soil. Tomographic images are presented for different objects in different soils (.5 to 5 GHz and 2 to 8 GHz bandwidths) that show the quality of the results delivered by this improved technique. Conclusion are drawn on the potentialities and the limitations of the method and future perspectives like 3D imaging.

Combined in space and in time microwave Doppler-radar- radiometer system is described. Doppler-scatterometer- radiometer detector-identifier is developed, for a detection and identification 16 types of anomalies originated on a background of observed surface or medium due to the changes of their principal geophysical and biochemical characteristics.

A 3D FDTD simulator is implemented for the detection of an underground tunnel by employing a cross-borehole pulse radar. The antenna and underground tunnel are modeled equivalently by employing the thin-wire model and the contour-path scheme, respectively. In various underground situations, the received radar signals are calculated numerically. But the FDTD simulator requires large computational resources because its spatial sampling grid is very fine. As a detour, a hybrid FDTD/PSTD method is suggested here. Since the spatial sampling grid of PSTD is coarser than that of FDTD, the hybrid FDTD/PSTD method may be expected more efficient than the FDTD method. The possibility of a hybrid FDTD/PSTD simulator is verified in a simple 1D case.

Theoretical and numerical analyses of the radiation directivity of a guiding radar system based on leaky coaxial cable (LCC) are presented both for buried and open installations in clutter conditions. The theoretical model of fields generated by a cable buried in a lossy half-space, such as a sub-soil medium, is introduced to describe the working characteristics of such a leaky coaxial cable. A numerical procedure which describe various kinds of LCC installations and can predict the effective characteristics of a radar system based on an LC with required parameters including its directional properties, is proposed to analyze the clutter effects and to optimize the sensitivity of such a radar system both for open and buried installations. The distribution of radiation around the cable is examined numerically by use of the LCC buried at depth d in a sub- soil medium, as well as open installation near different kinds of wall. The radiation pattern of such a radar system across the cable installed at height h above the ground is also investigated.

In this contribution the various influences on the accuracy of a near range precision radar are described. The front-end is a monostatic design operating at 34 - 36.2 GHz. The hardware configuration enables different modes of operation including FM-CW and interferometric modes. To achieve a highly accurate distance measurement, attention must be paid to various error sources. Due to the use of a six-port it is rather complicated to determine the corresponding error propagation. In the following the results of investigations on how to achieve an exceptional accuracy of +/- 0.1 mm are described.

An accurate simulator of a GPR system is implemented by using the FDTD method. To calculate numerically the receiving responses for an actual GPR system, the simulation space contains the equivalent models of transmitting and receiving antennas, antenna feeds, dispersive ground, and buried target. Several GPR simulators were presented in literature, but all of them required additional signal processing procedures or an assumption of non-dispersive ground medium. Recently, some improved techniques of antenna modeling and the PML absorbing boundary condition for dispersive or layered media were extended by several investigators. In this paper, therefore, the conventional simulations are improved by introducing the extended techniques. An actual measurements of a GPR system with fabricated antennas is accomplished above a PVC tank filled with dry sand in our laboratory. The validity of our simulation is assured by comparing the FDTD results with the measurement data of the received voltages for a GPR in the same situation. Our simulator may be used as an effective tool in optimal design as well as performance improvement of a GPR system.

A hybrid method that combines two numerical techniques, the Finite Difference Time Domain and the Method of Moments in the Time Domain, is employed to study the behavior of thin- wire, broadband antennas in the proximity of arbitrary inhomogeneous media and, in particular, to simulate a 3D model of a short-pulse ground penetrating radar.

This work is devoted to the diffraction tomography in millimeter wavelength band. It is used for reconstruction of the images of volumetric objects. With the help of this method one can study internal structure of distant nondestructive objects.

In this paper results of investigations of frequency response of ground penetrating radar are given. Radar throughput frequency response can be represented by product of frequency response of transmitter antenna, of propagation medium, of radar cross-section of object and of receiver antenna. Frequency response of propagation medium depends on distances from transmitter and received antennas to the object, and on electrical parameters of medium. Usually frequency responses of receiver and transmitter antennas are identical to match receiver frequency response and transmitted signal spectrum. However, in subsurface sounding the propagation medium (ground) is dispersive due to frequency dependence of dielectric permittivity and absorption coefficient. Dispersive distortions of signal spectrum are not negligible, because signals used in subsurface sounding are broadband with relative bandwidth more than 2. Besides, a large class of objects can be described as quasi-point (quasi-linear), with one of the dimensions being smaller than mean wavelength of sounding signal.

Attenuation and broadening of georadar signals in moist sandy- clayey soils was modeled depending on clay content and moisture of a soil. Antennas are of the slot type and are situated on the face of a tunneling machine. The pulse, radiated and received by this antennas and reflected by a perfectly conducting layer or small dielectric objects, was considered. Modeling has been carried out by integral equation method. For given signal to noise ratio the maximum distance of sounding have been calculated. The distance of sounding has been considered depending on size of the antennas, duration and shape of source pulse. The shape of signals depending on distance of sounding and soil parameters have been studied. To find dielectric permittivity of soils in wide frequency range a simple model was used, which takes into account the conductivity of the soil, dipole water relaxation and very wide spectrum of relaxation frequencies in clayey soils, which is due to Maxwell-Wagner effect in clay. Dielectric permittivity of several clayey soils, taken from tunnels, has been measured, and the model of soil has been adjusted with these experimental data.

Interference figures are often subject of interest in subsurface sensing technologies. Proper further processing of them is essential for interpretation of data covered in such images. This interpretation is often possible after recognition of the interference patterns. The article presents pattern recognition system suitable for dealing with interference figures. The system consists of optimized computer-generated hologram used for feature extraction and artificial neural network used as classifier of features. This pattern recognizer was tested with images of intermodal interference occurring in the optical fiber. If the fiber is embedded in the polymer composite material then such subsurface sensor together with mentioned pattern recognition system can be used for determining stress and distortion of that material. Since polymers are wide utilized for different constructions, including airplane wings, presented hybrid system can be used for real time, nondestructive monitoring of working stresses occurring in these constructions. The recognition of critical compressive stress can be therefore an early alarm signal of possible forthcoming danger.

The imaging systems (with the quality of the radioimages `equal' to the optical images of the targets) based on haven't got any analogies in the methods of the `isotropic radiovision' are suggested. The most important fields of applications of this methods are: imaging radar, security systems, custom control systems, AVC and AVI systems.

Slot antennas and shielded dipole antennas, including resistive material or resistive elements, are considered. Numerical modeling has been carried out by finite difference method in time domain and by integral equation method in frequency domain. The following characteristics has been studied: `front to back' ratio, near field patterns for pulse radiation, far field patterns and energy flux distribution in frequency domain, gain to the ground and the air, input impedance, transient response. An influence of the spacing between the antennas and the ground was studied. Several ways of using of resistive elements and covering were considered: placing of the resistive material into the spacing and around slot antennas, between the dipole and it's screen, including of resistive elements to the bottom surface of the slot antenna, resistive screen of slot antennas. Some optimal antennas have been found. Influence of antenna's design to characteristics is shown. Dipole antenna with a resistive material between the dipole and the screen may provide greater front to back ratio, then the slot antennas, having the same size. Slot antenna with resistive covering on lateral sides ensures high front to back ratio when it is placed on the ground. Optimal conductivity of resistive covering around slot antennas have been found depending of type of the covering and conductivity of the ground.

Detailed physical model of dielectric permittivity of sandy- clayey soils is proposed. The model is based on mixture formulas, which are applied in several steps, by which different components of the soil are successively combined. Several mixture formulas have been tested when applied to mixtures with flattened and spherical inclusions. For a mixture with very flattened inclusions Maxwell Garnett's mixture formula gives most accurate results. It is shown, that Maxwell-Wagner effect in clay in frequency range from approximately 1 - 5 to several hundreds MHz may be described by Maxwell Garnett's and Bruggeman's formulas. Five models are proposed to describe the Maxwell-Wagner effect in clay. Results of modeling are compared with results of measurements. The models with few parameters, adjusted for a given clayey soil, describe this soil depending on moisture and temperature, including a range below 0 degree(s)C. These parameters depend only on soil and do not depend on moisture and temperature. The model of soil takes into account distribution of water between clay and soil solution, change of thickness of bound water layers depending on moisture and when freeze. Conductivity of bound water, it's temperature dependence have been found for some soils. Debye relaxation spectrum of bound water was studied.

The problem of aerosol media parameters measurements are presented in the work and these media are used for the treatment of the patients with bronchial asthma moreover we show the results of the development and the concentration and dispersity of the particles for the long-term monitoring under such conditions when the aggressive surroundings are available. The system for concentration measurements is developed, which consists of two identical photometers permitting to carry out the measurements of the transmission changes and the light dispersion depending on the concentration of the particles. The given system permits to take into account the error, connected with the deposition of the salt particles on the optical windows and the mirrors in the course of the long-term monitoring. For the controlling of the dispersity of the aggressive media aerosols the optical system is developed and used for the non-stop analysis of the Fure-spectra of the aerosols which deposit on the lavsan film. The registration of the information is performed with the help of the rule of the photoreceivers or CCD-chamber which are located in the Fure- plane. With the help of the developed optical system the measurements of the concentration and dispersity of the rock-salt aerosols were made in the medical mines of Solotvino (Ukraine) and in the artificial chambers of the aerosol therapy.

The relatively simple measuring methods for determining the complex permittivity and the complex permeability of magnetodielectric materials are presented. Measurement must be done with each sample of any magnetodielectric by two methods: the short circuit method and the idling method. For measurements by the short circuit method, a magnetodielectric sample is placed in the measuring waveguide near the short circuit end. For measurements by the idling method, a magnetodielectric sample is placed in the measuring waveguide at a quarter of the wavelength distance from the short circuit end. The measurements are taken equally for both methods. The measuring waveguide (with a sample) is connected to the standard measuring line. The other end of the measuring line is connected to a transmitter. A transmitter radiates waves of a given frequency, they are reflected by the short circuit end of a measuring waveguide containing a magnetodielectric sample and standing waves are set up. Standing wave parameters can be measured by the standard measuring line and the indicator.

New possibilities of the FT-IR technique in situ studying of the vibrational relaxation processes occurring in the chromophores during the optical excitation have been successfully performed. The major advantage of this method lies in the ability to obtain in situ vibrational spectroscopic information under normal conditions. The IR- emission spectra of the thin film as well as a diluted solution of rhodamine 6G (Rh6G) are presented for illustration. It was shown that the infrared radiation in main part was due to the transitions within the vibrational manifold of the ground electronic state. Evidence was obtained that the vibration structure of the Rh6G molecule was altered upon optical excitation. The high sensitivity and nondestructive character of FT-IR emission spectroscopy enable advantageous use in other systems, including biomembrane and biological macromolecules.

Hyperspectral imaging has been shown to be useful for producing qualitative maps of the concentration of hemoglobin in skin, and quantitative maps of its oxygen saturation. These maps provide information about the health of the skin, which may be useful in medical diagnosis and in planning intervention for skin lesions. Wavelengths have usually been determined on a somewhat intuitive basis using spectra based on analytical models. In the present work, we demonstrate a means of selecting wavelengths from a data cube of experimental data.

Acousto-photonic imaging is a novel technique for non- invasive medical imaging that combines diffusive optical tomography with externally generated acoustic `virtual' sources to improve the resulting images. We lack, however, a detailed understanding of the nature of the interaction between the diffusive wave and the focused ultrasound. We present our recent theoretical and experimental work on determining the mechanism for the interaction between the acoustic and the optical fields.