Seong-Jun Cho

Removal of ringing noise in GPR data by signal processing

Ringing is a common type of coherent noise in ground penetrating radar (GPR) data. When this kind of coherent noise is strong and is not properly removed, deeper structure may be completely masked. Ringing appears as nearly horizontal and periodic events, which are the most important features enabling us to remove the noise by signal processing. In this study, we have reviewed basic principles of various signal processing techniques to remove the ringing noise and compared their performances using field GPR data contaminated by severe ringing noise. The reviewed methods include background removal. f-k filtering, predictive deconvolution with filtering in wavenumber domain, and filtering by radon transform. Furthermore, it is shown that ringing can be successfully removed by the eigenimage filtering method, where GPR image is decomposed into eigenimages by singular value decomposition. This comparative analysis shows that the refined techniques are definitely more effective than the simple methods for the ringing noise removal with less distortion of GPR signals and each method has its own advantage as well as limitations. Moreover, preservation of the horizontally linear events from geological targets can be possible only through a kind of selective or local filtering such as the eigenimage filtering method.

Development of a Truck-Mounted Arc-Scanning Synthetic Aperture Radar

This paper presents the development of a ground-based arc-scanning synthetic aperture radar (ArcSAR) system mounted on a truck. ArcSAR formulates synthetic aperture by a horizontal circular motion of antennas attached at the end of an extendable boom. The ArcSAR system is designed to operate in two different imaging modes: the spot mode and the scan mode . The spot mode obtains a high-resolution image by fixing the view angle of antennas toward a target. The scan mode obtains wider image coverage with a reduced resolution by fixing the antennas relative to the boom. Different SAR focusing algorithms were implemented for the accuracy and efficiency of image processing: the time domain algorithm for the spot mode and the range Doppler algorithm for the scan mode. An exemplary X-band ArcSAR spot mode image, obtained with a 180 ° scanning of 4-m boom, has an azimuth resolution of 0.07 ° , which is equivalent to the 12.6-m linear scanning of a conventional ground-based SAR system. An ArcSAR scan mode image was successfully obtained as well, covering a 350 ° image area at an azimuth resolution of 1.07 °, which is 11 times better than that of arc-scanning real aperture radar that would have 11.84 ° azimuth resolution.

Anisotropic Crosshole Resistivity Tomography for Ground Safety Analysis of a High-Storied Building Over an Abandoned Mine

Crosshole resistivity tomography was performed to image the subsurface structures and mine cavities beneath a 25 story apartment building constructed at an abandoned mining site, and to provide the underground model for the safety analysis of the building. Strong electrical anisotropy was observed in the measured data, which has proven to be mainly due to geology. In order to deal with the anisotropy effect and to reconstruct the subsurface images reflecting the underground status precisely, we developed anisotropy inversion codes for resistivity tomography. The algorithm is based on finite element approximations for the forward modeling; the ACB (Active Constraint Balancing) method was adopted in the program in order to enhance the resolving power of the smoothness constraint least-squares inversion. All the acquired data were inverted by the developed inversion code so as to reconstruct the subsurface images, which match quite well with the geological mapping result. In particular, the locations of cavi...

Radar Backscattering of Intertidal Mudflats Observed by Radarsat-1 SAR Images and Ground-Based Scatterometer Experiments

This paper presents the variation of the radar backscattering of intertidal mudflats in the west coast of Korea observed by Radarsat-1 synthetic aperture radar (SAR) images and investigates the related factors by an indoor experiment and a field experiment using a ground-based C-band scatterometer. The 15 Radarsat-1 SAR images of the intertidal mudflat near Jebu Island used in this study were all taken at around 6:30 p.m., which is an ideal local time for evaluating the daytime evaporation effects during the 12.4-h tidal cycle. An exposure time map and an evaporation time map of mudflats at the time of each SAR acquisition are calculated based on the tidal records, a digital elevation map generated by the waterline extraction method, and the normalized daily evaporation index. The radar backscattering of the upper intertidal mudflat did not show a monotonic change with evaporation time but a complex pattern. An indoor experiment using a C-band scatterometer on drying mud revealed an M-shaped change (increase-decrease-increase-decrease) of radar backscattering due to various factors that affect dielectric constant and roughness such as the drainage of surface water (increase), evaporation (decrease), mud cracking (increase), and further evaporation (decrease). The variation of backscattering observed from SAR images agreed well with the initial three stages of the indoor experiment (increase-decrease-increase) but did not show the final stage of decrease from continuous evaporation. A field experiment on natural intertidal mudflats showed not only the pattern related to the initial drainage and evaporation but also speckles from biological activity.

Effective 3D GPR survey and its application to the exploration of old remains

Since the buried cultural relics are three-dimensional (3D) objects in nature, 3D survey is more preferable in archeological exploration. 3D ground penetrating radar (GPR) survey based on very dense data in principle, however, might need much higher cost and longer time of exploration than other geophysical methods. We developed a small-scale continuous data acquisition system which consists of two sets of GPR antennas and the precise positioning device tracking the moving-path of GPR antenna automatically and continuously. Besides this hardware system, we adopted a concept of data acquisition at arbitrary locations not along the pre-established profile lines, since the high cost of field work may be partly attributed to establishing many profile lines. Using the developed system, we performed 3D GPR survey to investigate the possible historical remains of Baekje Kingdom at Buyeo city, South Korea, prior to the excavation. Owing to the newly devised system, we could obtain 3D GPR data of this survey area having a real extent over about 17,000 m/sup 2/ within only six-hours field work. Although the GPR data were obtained at random locations not along the pre-established profile lines, we could obtain high-resolution 3D images showing many distinctive anomalies, which could be interpreted as old agricultural lands, waterways, and artificial structures or remains. This case history led us to the conclusion that 3D GPR method is very useful not only to examine a small anomalous area but also to investigate the wider region of the archeological interests.

Γ-glutamyl transferase as an early and sensitive marker in ethanol-induced liver injury of rats.

γ-Glutamyl transferase (GGT) has been regarded as a biological marker of heavy alcohol consumption or hepatobiliary disease such as fatty liver. However, the role of GGT is unknown in the molecular pathway during alcohol-induced liver injury. To determine the role of GGT in alcohol-induced liver injury, Sprague-Dawley rats were administered 22% and 38% ethanol for 3 days as acute and 5 weeks as subchronic model. In serologic analysis, the level of GGT was significantly increased and the level of alanine aminotransferase, aspartate aminotransferase, and total bilirubin were not changed at 3 days and 5 weeks. In histologic analysis, ethanol exposure induced granular deposit formation and sinusoidal dilation in the acute model for 3 days. In the subchronic model for 5 weeks, ethanol exposure further increased the granular deposit formation, sinusoidal congestion, and mild fatty liver change. To determine whether ethanol-exposed liver is associated with changes of antioxidants levels, we performed reverse-transcriptase polymerase chain reaction (RT-PCR) analysis on ethanol-exposed livers of rats. In RT-PCR analysis, the mRNA levels of GPX1 and SOD1 were significantly increased as well as up-regulation of CYP2E1. In the glutathione assay, the level of glutathione was significantly reduced in response to ethanol in rats. Therefore, in this study, ethanol increased the level of serum GGT but depleted the level of glutathione. Moreover, the CYP2E1 was rapidly reflected to ethanol in rats. Taken together, our findings suggest that the elevated GGT is associated with cellular antioxidant defense system, and the CYP2E1 can be used for early diagnosis in alcohol-related diseases.

Mineral Potential Mapping of Gagok Mine Using 3D Geological Modeling

In order to develop an effective mineral exploration technique, this study was carried out about the potential mapping of Gagok mine. The deposit model of Gagok mine is widely known. Based on the deposit model, we constructed mining indicator indices using related igneous rocks, faults, and carbonate rocks. By analyzing the spatial correlation between ore and indicator index structures, we decided the weighting values of indices according to the distance from the index structure. The 3D potential mapping was performed using 3D geological model and geological indices. The analyzed potential map verified that the locations and patterns of high potential regions of the results were well matched with those of the known ore bodies. Using the potential mapping results, we could effectively predict the location of a high potential area that has similar geological settings with ore.

A ground-based Arc-scanning synthetic aperture radar (ArcSAR) system and focusing algorithms

KIGAM and KNU are developing a ground-based Arc-scanning SAR system (ArcSAR) mounted on a truck. The system achieves the coherent integration of radar returns from ground targets by the circular motion of the antennae attached to the end of an extendable arm. Precise control of antenna position and the extended coherent-integration-length enable the formation of high-resolution, high-precision and phase-preserving SAR images. Based on the Polar Format Algorithm, two SAR-focusing algorithms were developed for the data acquired from two different scanning modes of this unique system: the scan mode and the spot mode.

Evaluation of Acid-concentrated Soybean Meal as a Fishmeal Replacement and its Digestibility in Diets for Juvenile Olive Flounder Paralichthys olivaceus

This study was conducted to investigate the effects of fishmeal replacement with acid-concentrated soybean meal (ACSBM) on growth performance, blood biochemistry, and ingredient digestibility in juvenile olive flounder Para-lichthys olivaceus. Six experimental diets were formulated to replace fishmeal protein with ACSBM at 0%, 20%, 30%, 40%, 50%, and 60% (designated ACSBM0, ACSBM20, ACSBM30, ACSBM40, ACSBM50, and ACSBM60, respectively). Triplicate groups of fish (initial fish mean weight: 14.3±0.03 g) were fed the experimental diets to apparent satiation (twice daily at 08:00 and 18:00 h). After a 12-week feeding trial, a total of 180 healthy fish were randomly distributed into three Guelph system tanks at a density of 60 fish/tank (initial fish mean weight : 50.6±2.4 g) to test the apparent digestibility coefficients of the ingredients (ACSBM, fishmeal, and soybean meal). Although negative effects were observed with ACSBM40, ACSBM50 and ACSBM60 after 12 weeks of feeding, up to 20% of the fishmeal protein could be successfully replaced with ACSBM without significant growth depression. Hemoglobin and hematocrit values of fish fed the ACSBM50 and ACSBM60 diets were significantly lower than those of fish fed the ACSBM0 diet. Glucose values of fish fed the ACSBM60 diet were significantly higher than those of fish fed the ACSBM0 and ACSBM20 diets. Digestibility of protein in ACSBM and soybean meal was 85.9% and 82.5%, respec -tively. Results indicated that at least 20% of fishmeal protein can be replaced by ACSBM in diets of juvenile olive flounder without supplementation of limiting amino acids. Key words: Olive flounder, Fish meal, Acid-concentrated soybean meal, Digestibility, Replacement

Wishart supervised classification results of C-band polarimetric GB-SAR image data

The objective of this paper is a classification and analysis of a fully polarimetric ground based synthetic aperture radar (GB-SAR) image to discriminate the different terrain media. Wishart supervised classification method was applied to classify the fully polarimetric GB-SAR data and the refined Lee filter for reducing a speckle noise. We discussed about the classification results of the obtained GB-SAR.