Reliability of signal processing technique for pavement damages detection and classification using ground penetrating radar

Ground penetrating radar (GPR) signal processing is a nondestructive technique, currently performed by many agencies involved in road management and particularly promising for soil characteristics interpretation. The focus of this paper is to assess the reliability of an optimal signal processing algorithm for pavement inspection. Preliminary detection and subsequent classification of pavement damages, based on an automatic GPR analysis, have been performed and experimentally validated. A threshold analysis of the error is carried out to detect possible damages and check if they can be predicted, while a second threshold analysis determines the nature of the damage. An optimum detection procedure is performed. It implements the classical Neyman-Pearson radar test. All the settings needed by the procedure have been estimated from training sets of experimental measures. The overall performance has been evaluated by looking at the usual receiver's operating characteristic. The results show that a reasonable performance has been achieved by exploiting the spatial correlation properties of the received signal, obtained from an appropriate analysis of GPR images. The proposed system shows that automatic evaluation of subgrade soil characteristics by GPR-based signal analysis and processing can be considered reliable in a number of experimental cases.     

Effect of antenna dimensions on the antenna footprint in ground penetrating radar applications

Ground penetrating radar (GPR) surveys show that antenna characteristic is strongly influenced by soil conditions. The footprint of the antenna is an important parameter for a good detection result. Various conditions of soil in which a target is buried may change the footprint of the antenna. An antenna with capability to control its footprint is needed in GPR applications. In this study, the authors investigate several ultra-wideband (UWB) antennas with different dimensions to study the effect of antenna dimension on their footprint. Simulation and experiments show that large (small) antenna dimensions result in a large (small) antenna footprint when the observation is located in the near-field region. When the observation is located in the far-field, the footprint of the antenna becomes large (small) if the dimensions of the antenna are small (large). Thus, the size of the antenna footprint can be adjusted by varying the antenna dimension. It is applied in this work to develop a new method for controlling the antenna footprint to deal with varying soil condition. Measurements have been carried out to validate this concept.     

Detection of chlorides and moisture in concrete structures with ground penetrating radar

Corrosion of re-bar within reinforced concrete is a major problem in countries where salt is applied to roads for de-icing. Concrete structures are periodically inspected in order to monitor possible damage caused by chloride induced corrosion of the reinforcement. However, bridge decks covered with asphalt pavements are not accessible for visual inspection and probing is limited. As a result, the planning of rehabilitation of bridge decks is usually based on a small number of probes. Consequently, the condition of bridge decks can only be assessed with low certainty. Therefore, a method enabling to study the conditions of concrete bridge decks covered by asphalt pavements is desirable. This paper describes a laboratory experiment aiming at the investigation of the effects of moisture and chloride content on the amplitudes of radar signals. It can be shown that both, moisture and chloride content have a measurable influence on signal amplitudes. This may enable the future use of ground penetrating radar for the planning of probing campaigns or for the extrapolation of results obtained at single probing points.     

Calculation of the temperature of frozen ground on the basis of mathematical models of the temperature dependence of ground penetrating radar signals

Procedural questions related to the construction of mathematical models that establish a quantitative relationship between certain characteristics of the temperature field and the indicator of damping of the pulse electromagnetic field in a layer of the annual temperature fluctuations of built-up areas of the cryolithic zone of Yakutia are considered. Recommendations are given for practical application of the mathematical models based on an analysis of the errors that arise when calculating the temperature of frozen ground found with the use of the models.     

Optimization and integration of high‐performance ground penetrating imaging radar system: A research prototype

This paper reports the design, development, and field experimentation of a new ground penetrating imaging radar system. This research prototype unit features full system optimization, which successfully integrates the key components of antenna sensitivity, data‐acquisition waveforms, synthetic‐aperture scan, and image reconstruction algorithms, for optimal system performance.© 2006 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 15, 220–223, 2005     

Fractography and structure of the subsurface cleavage zone in molybdenum

Transmission electron microscopy of thin foils was used to examine the structure of fracture surfaces of single crystals of molybdenum failed by cleavage along different crystallographic planes, and the dislocation structure of the zone adjacent to the fracture surface was also studied. The results show that cleavage steps are the main characteristic element in failure along any plane in the group of the examined planes ({100}, {110}, {211}, {123}). The number, dimensions, and crystal geometry of the cleavage steps depend on the cleavage plane. The primary cleavage elements are steps of the minimum size (height 8–17 nm). The results also show that with an increase of the work used in failure in transition from one cleavage of macroplane to another the thickness of the zone with high (in comparison with the initial value) dislocation density increases together with the dislocation density directly on the fracture surface.Translated from Problemy Prochnosti, No. 1, pp. 58–63, January, 1991.     

Features of the procedure for measuring the amplitude backscattering diagrams of very large objects using ground radar measuring systems

A procedure for measuring the backscattering diagrams of large objects is considered, which reduces the components of the error due to the long-term instability of the parameters of radar measuring stations, when using a calibration without removing the object being investigated from the operating region of the measuring system. The results of an experimental check of the procedure are presented. __________ Translated from Izmeritel’naya Tekhnika, No. 6, pp. 48–50, June, 2008.     

Low radar cross-section and high performances of microstrip antenna using fractal uniplanar compact electromagnetic bandgap ground

By using surrounding periodic second-uniplanar compact electromagnetic bandgap (UC-EBG) ground plane, a microstrip patch antenna working at X-band with low radar cross-section (RCS) and high performance was designed. The main parameters such as return loss, impedance bandwidth, RCS, radiation patterns and gains are presented and discussed. Comparison of the patch antenna with the surrounding periodic second-UC-EBG ground suggests that the second-UC-EBG has much lower RCS than the standard patch antenna at a band range 2-18 GHz. In addition, gain, bandwidth and radiation patterns of the former are all improved when compared with those of the latter.     

Mapping of potential gradients within the electrospray emitter

A novel electrochemical probe has been designed, built, and used to characterize the distribution in solution potential within the metal capillary and Taylor cone of the electrospray (ES) device. The measurement system consists of three electrodes-a counter electrode held at highly negative potential that serves as the cathode, and two anodes consisting of a disk-shaped, mobile, internal (working) electrode, and the internal surface of the surrounding ES capillary (auxiliary electrode, held at ground potential). One-dimensional differential electrospray emitter potential (DEEP) maps detailing solution potential gradients within the electrospray emitter and in the region of the Taylor cone are constructed by measuring the potential at the working electrode vs the ES capillary, as a function of working electrode position along the emitter axis. Results show that the measured potential difference increases as the internal probe travels toward the ES capillary exit, with values rising sharply as the base of the Taylor cone is penetrated. Higher conductivity solutions exhibit potentials of higher magnitude at longer distances away from the counter electrode, but these same solutions show lower potentials near the ES capillary exit. Removal of easily oxidizable species from the solution causes the measured potential difference to have nonzero values at distances further within the capillary, and the values measured at all points are raised. Results are consistent with the characterization of the electrospray system as a controlled-current electrolytic flow cell. Elucidation of the electrochemical details of the electrospray process can lead to mass spectrometric signal enhancement of certain species present in the spraying liquid and also allow the detection of molecules that are usually not observable due to their low ionization efficiencies.     

The values of J-integral within the plastic zone

A study has been conducted to characterize the J-integral within the plastic zone for different strain hardening materials. The relation between the calculated J-integral and plastic energy enclosed by the selected integration contour is explored for different strain hardening materials. The equations between the J-integral and plastic energy around the crack tip for 7075-T651 aluminum alloy and HY-130 steel have been derived. It is shown that the J-integral is path dependent if the selected integration contour goes across the plastic zone. Results also indicated the plastic energy enclosed by the selected integration contour provides the dominant contribution to the J-integral.     

Biodegradation of RDX within soil-water slurries using a combination of differing redox incubation conditions

Biodegradation of 14C-tagged hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) was studied in aerobic, anaerobic, and anaerobic/aerobic slurries to identify the conditions maximizing RDX-mineralization in Cornhusker Army Ammunition Plant (CAAP, NE) groundwater. Supplementation with phosphate and adequate quantities of acetate caused 25% mineralization of RDX in 3 weeks by microorganisms native to CAAP. Under anaerobic conditions, the same supplementation resulted in 20% mineralization in 3 weeks and 30% mineralization in 6 weeks. The highest degree of mineralization (50%) was obtained under aerobic conditions when the contaminated groundwater was augmented with a consortium of three microbes isolated from another RDX contaminated soil (Hastings, NE) in addition to supplemented with phosphate and acetic acid. Use of complex organic sources (potato or corn starch) slowed down the rates of mineralization under anaerobic conditions, but rapid mineralization ensued as soon as the aerobic conditions were created. Final RDX concentrations in aqueous phase were below detection limit under most conditions. Assimilation of RDX by the cells was negligible.     

A Constraint Mapping Approach to the Structural Optimization of an Expensive Model using Surrogates

The use of response surface methods are well established in the global optimization of expensive functions, the response surface acting as a surrogate to the expensive function objective.In structural design however, the change in objective may vary little between the two models: it is more often the constraints that change with models of varying fidelity. Here approaches are described whereby the coarse model constraints are mapped so that the mapped constraints more faithfully approximate the fine model constraints. The shape optimization of a simple structure demonstrates the approach.     

Estimation of admissible loads upon a pipeline in the zone of sliding ground

We propose a computational scheme for the evaluation of admissible arbitrarily oriented loads acting upon a pipe in the zone of sliding ground.Department of Main Pipelines PrykarpattransgasTranslated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 4, pp. 98–100, July–August, 2004.     

Effect of shields on radiative heat transfer within the penetration zone

A procedure is proposed for calculating the effect of thin floating shields and of cooled cylindrical shields on radiative heat transfer within the penetration zone.Translated from Izhenerno-Fizicheskii Zhurmal, Vol. 23, No. 4, pp. 627–634, October, 1972.     

Mapping interactions within the evolving science of science and innovation policy community

The Science of Science and Innovation Policy (SciSIP) program at the National Science Foundation (NSF) supports research designed to advance the scientific basis of science and innovation policy. The program was established at NSF in 2005 in response to a call from Dr. John Marburger III, then science advisor to the U.S. President, for a “science” of science policy. As of January 2011, it has co-funded 162 awards that aim to develop, improve, and expand data, analytical tools, and models that can be directly applied in the science policy decision making process. The long-term goals of the SciSIP program are to provide a scientifically rigorous and quantitative basis for science policy and to establish an international community of practice. The program has an active listserv that, as of January 2011, has almost 700 members from academia, government, and industry. This study analyzed all SciSIP awards (through January 2011) to identify existing collaboration networks and co-funding relations between SciSIP and other areas of science. In addition, listserv data was downloaded and analyzed to derive complementary discourse information. Key results include evidence of rich diversity in communication and funding networks and effective strategies for interlinking researcher and science policy makers, prompting discussion, and resource sharing.     

带覆盖层半空间内SH波对浅埋圆孔及夹杂散射与地震动

采用大圆弧假定法将具有地表覆盖层的半空间直边界问题转化为曲面边界问题。借助Helmholtz定理预先给出问题波函数的一般形式解,再利用复变函数法及边界条件将问题化为求解波函数未知系数的无穷线性代数方程组,截断该方程组即可求解带地表覆盖层的半空间内浅埋圆孔及夹杂对SH波散射问题,并给出地面运动数值结果。定性分析入射波数、入射角度、埋深、夹杂刚度及覆盖层刚度等对地面运动影响。研究表明,浅埋圆孔及夹杂与地表覆盖层间存在强烈的相互作用,地震动会受较大影响。     

Single-pulse measurement of wind velocities using an Er:Yb:glass coherent laser radar

Many wind-field mapping applications require range-resolved atmospheric velocity measurements at long range and/or with a temporal resolution sufficient to investigate turbulence. We argue that this capability can be achieved only by coherent laser radar systems that transmit energetic (>1 mJ) pulses. We describe such a system and describe single-pulse measurement of the range-resolved line-of-sight velocities, and show that the instrument-limited reproducibility of the measurements is 0.4 ms(-1).