The Experts below are selected from a list of 133740 Experts worldwide ranked by ideXlab platform

Feng Liu - One of the best experts on this subject based on the ideXlab platform.

  • geometric distortion characterization and correction for the 1 0 t australian mri linac system using an inverse Electromagnetic Method
    Medical Physics, 2020
    Co-Authors: Shanshan Shan, Gary P Liney, Fangfang Tang, Yaohui Wang, Ewald Weber, Amy Walker, L Holloway, Qiuliang Wang, Deming Wang, Feng Liu
    Abstract:

    Purpose The magnetic resonance imaging (MRI)-Linac system combines a MRI scanner and a linear accelerator (Linac) to realize real-time localization and adaptive radiotherapy for tumors. Given that the Australian MRI-Linac system has a 30-cm diameter of spherical volume (DSV) with a shimmed homogeneity of +/- 4.05 parts per million (ppm), a gradient nonlinearity (GNL) of = 1.5-mm distortions from 6.3% to 1.3%, indicating substantially improved geometric accuracy. Conclusions The experimental results indicated that the proposed Method could provide substantially improved geometric accuracy for the region outside of the DSV, when comparing with the fifth-order SH-based Method.

Guoqiang Xue - One of the best experts on this subject based on the ideXlab platform.

  • The optimal survey area of the semi-airborne TEM Method
    Journal of Applied Geophysics, 2020
    Co-Authors: Da Lei, Ya Gao, Zhu Jun, Guoqiang Xue
    Abstract:

    Abstract The semi-airborne transient Electromagnetic Method (TEM) has been widely used in resource exploration and other fields due to its high efficiency, strong adaptability to the complex environment and high resolution. However, the conventional semi-airborne Electromagnetic Method continues to use the survey area of the grounded-wire TEM Method. Compared with the existing ground-based TEM Method, the semi-airborne TEM Method is more sensitive to signal intensity because observed data is easily affected by noise for receiving position in the air. Therefore, it's unreasonable to consider only signal intensity or sensitivity related to offset in survey area. To obtain more suitable area, we discuss the distribution of the transient Electromagnetic field with electrical source as well as the attenuation characteristics of the signal at different flight altitude through the forward modeling. Then, we obtain the sensitive area and flight altitude applied by the error analysis Method in typical models. Finally, we describe a Method what is herein dubbed the fuzzy comprehensive evaluation, which greatly reflects the membership degree of the evaluation object from different single factors to each level of fuzzy subset. Therefore, we use this Method to get the optimal survey area and flight altitude under different noise levels. In low noise level, the signal intensity and sensitivity account for 33.3% and 66.7% respectively in selecting the optimum area and altitude, resulting in that the optimal area and flight altitude are coincides with the sensitive area and altitude better. While in the area filled with noise, the most area of strongest signal intensity is considered the optimal area and altitude. A field example shows that the aforementioned Method can be well resolved in identifying survey lines and improving data quality.

  • magnetic viscosity effect on grounded wire tem responses and its physical mechanism
    IEEE Access, 2020
    Co-Authors: Linbo Zhang, Guoqiang Xue, Wen Chen
    Abstract:

    Magnetic viscosity (MV) effect is a disturbance to the transient Electromagnetic Method (TEM). This effect will cause slow decay at the intermediate-late time of the TEM responses, leading to erroneous interpretation. Although there are extensive researches on the MV distortion to TEM data, they are focused on conventional loop source configuration, while little has been studied for grounded-wire source configuration that has become the essential role for relatively deep-buried targets. Hence, we present the study of MV effect on the grounded-wire source TEM data. We first derived the formulas for calculating the secondary field due to MV effect, based on the Chikazumi model. The dependence of the MV effect on model parameters, such as resistivity, susceptibility, offset and geometry of the superparamagnetic layer, is then examined to illustrate the intrinsic physical mechanism of MV effect. We find that the MV effect on the grounded-wire source TEM data can be suppressed by adjusting the parameters of the survey design. Thereafter, we propose the Method to quantify the MV effect when estimates of resistivity and susceptibility are available. Finally, the Method for choosing the optimal offset to suppress the MV effect is proposed, which can be used as a guide for the installation of fieldwork of grounded-wire TEM survey.

  • a review of electrical and Electromagnetic Methods for coal mine exploration in china
    IEEE Access, 2019
    Co-Authors: Guoqiang Xue, Wen Chen, Jiulong Cheng, Shucai Liu, Kangxin Lei, Wenbo Guo, Xihui Feng
    Abstract:

    During the past 20 years, due to the rapid development of China’s economy, the amount of coal mining activities has rapidly increased, which has led to a large increase in the number of mined-out areas. Therefore, the role of geophysical exploration in coal fields has changed from the detection of coal resources to engineering geological environmental investigation. The safety, efficiency, and green production of coal mines require more advanced geophysical detection technologies. In particular, the accurate detections of the locations of water-rich mined-out areas, as well as concealed water diversion channels, have become the main focuses of coal electrical Methods in recent years. Therefore, Electromagnetic Methods have become the main means of hydrogeological investigations and deep explorations in mine-out coal areas. In this study, a common DC Method was briefly introduced, along with an induced polarization Method. Then, three representative Electromagnetic sounding Methods, including a surface frequency-domain Electromagnetic Method, time-domain Electromagnetic Method, surface to air Electromagnetic Method, and mine Electromagnetic Method, were respectively introduced.

  • quasi mt inversion of short offset transient Electromagnetic data
    Pure and Applied Geophysics, 2016
    Co-Authors: Weiying Chen, Guoqiang Xue, Muhammad Younis Khan
    Abstract:

    The short-offset transient Electromagnetic Method (SOTEM) has been extensively used for mineral and hydrocarbon exploration and hydrogeological investigations due to its ease of use and capability to generate diagnostic subsurface information. At present, the data processing Methods of SOTEM are mainly focused on one dimensional inversion. To apply the proven inversion Methods of frequency domain Electromagnetic Methods to SOTEM data, this paper presents a new transformation relation from time to frequency based on the similarity between SOTEM all-time apparent resistivity and magnetotelluric (MT) apparent resistivity. Results show that the transformation coefficients depend on the variation trend of SOTEM all-time apparent resistivity curves. Bostick inversion and conjugate gradient inversion techniques were applied to transformed SOTEM data and the results were validated by some simulated calculations and field measured data. This study provides a novel Method to SOTEM data processing and a useful aid to join inversion with MT data.

  • detection and monitoring of water filled voids using transient Electromagnetic Method a case study in shanxi china
    Environmental Earth Sciences, 2013
    Co-Authors: Guoqiang Xue, Jiulong Cheng, Nannan Zhou, Weiying Chen
    Abstract:

    Shanxi Province is a major coal base for the rapid development in China, but heavy production of coal resources has left abundant water-filled voids, creating significant geologic hazards around coal mines. It is necessary to quickly investigate the position and distribution of voids with effective geophysical Methods. The feasibility of transient Electromagnetic (TEM) Method in detecting and monitoring water-filled voids is analyzed using 3D finite-element numerical simulation results as well as a case study in this paper. The case study was mainly to analyze and monitor the conditions around the site of a power transfer station under construction in the west of Shanxi province where many water-filled, mined-out voids existed. Central-loop TEM sounding was carried out three times from January 2010 to April 2011 around the building footprint. The low resistivity abnormal area had been repeatedly located and the survey results showed that the area of voids increased with time, which indicated that the ground at the site was in an unstable and dangerous state. The surveys provided more detailed geological information to the government for further safety arrangement and building re-design.

Shanshan Shan - One of the best experts on this subject based on the ideXlab platform.

  • geometric distortion characterization and correction for the 1 0 t australian mri linac system using an inverse Electromagnetic Method
    Medical Physics, 2020
    Co-Authors: Shanshan Shan, Gary P Liney, Fangfang Tang, Yaohui Wang, Ewald Weber, Amy Walker, L Holloway, Qiuliang Wang, Deming Wang, Feng Liu
    Abstract:

    Purpose The magnetic resonance imaging (MRI)-Linac system combines a MRI scanner and a linear accelerator (Linac) to realize real-time localization and adaptive radiotherapy for tumors. Given that the Australian MRI-Linac system has a 30-cm diameter of spherical volume (DSV) with a shimmed homogeneity of +/- 4.05 parts per million (ppm), a gradient nonlinearity (GNL) of = 1.5-mm distortions from 6.3% to 1.3%, indicating substantially improved geometric accuracy. Conclusions The experimental results indicated that the proposed Method could provide substantially improved geometric accuracy for the region outside of the DSV, when comparing with the fifth-order SH-based Method.

Kaushalendra Mangal Bhatt - One of the best experts on this subject based on the ideXlab platform.

  • microseisms and its impact on the marine controlled source Electromagnetic signal
    Journal of Geophysical Research, 2014
    Co-Authors: Kaushalendra Mangal Bhatt
    Abstract:

    The marine-controlled source Electromagnetic Method (mCSEM) is employed for studying the electrical characteristics and fluid contents of sedimentary reservoirs. However, the success rate of the Method can be improved significantly by finding the sources of Electromagnetic noise and addressing the challenge posed by them at larger offsets where the reservoir signal is often weak. I have studied the mCSEM data and reporting an Electromagnetic noise. The strength of the noise is observed 1600 times stronger than the seafloor mCSEM signal at 0.1 Hz. Moreover, the noise and the transmitted mCSEM signals are found coherent in interstation recordings. These readings suggest the severity of the noise. The source investigation presuming the observed noise as an infragravity wave failed to match the response. Then, the role of microseisms is investigated. Microseism causes oscillation of the seafloor and produces Electromagnetic disturbances by the dynamics of water. I have used various conditions for a proper discrimination of the noise as microseisms. This mechanism is clearly illustrated with the help of a conceptual diagram. The role of the directionality is part of the study, which is argued for having a significant role in the generation of microseisms. In this paper, a new algorithm is presented and is used for calculating the coherency. The algorithm helps in mapping the coherency value simultaneously in time and frequency domains.

David Wright - One of the best experts on this subject based on the ideXlab platform.

  • the potential of the controlled source Electromagnetic Method a powerful tool for hydrocarbon exploration appraisal and reservoir characterization
    IEEE Signal Processing Magazine, 2012
    Co-Authors: Antoni Ziolkowski, David Wright
    Abstract:

    In this article, we show that the controlled source Electromagnetic (CSEM) Method is complementary to the seismic Method.

  • multi transient Electromagnetic repeatability experiment over the north sea harding field
    Geophysical Prospecting, 2010
    Co-Authors: Antoni Ziolkowski, David Wright, Ronnie Parr, Victoria Nockles, Christopher Limond, Ed Morris, Jonathan Linfoot
    Abstract:

    We present results of synthetic time-lapse and real repeatability multi-transient Electromagnetic surveys over the North Sea Harding field. Using Archie’s law to convert porosity and fluid saturation to resistivity we created 3D isotropic models of the reservoir resistivity at different stages of production from the initial state in 1996 through to complete hydrocarbon production by 2016 and, for each stage, we simulated an east-west transient Electromagnetic survey line across Harding. Unconstrained 1D full-waveform Occam inversions of these synthetic data show that Harding should be detectable and its lateral extent reasonably well-defined. Resistivity changes caused by hydrocarbon production from initial pre-production state to production of the oil rim in 2011 are discernible as are significant changes from 2011–2016 during the modelled gas blowdown phase. The 2D repeatability surveys of 2007 and 2008 tied two wells: one on and the other off the structure. Between the two surveys the segment of the field under investigation produced 3.9 million barrels of oil – not enough to generate an observable time-lapse Electromagnetic anomaly with a signal-to-noise ratio of 40 dB. Processing of the 2007 and 2008 data included deconvolution for the measured source current and removal of spatially-correlated noise, which increased the signal-to-noise ratio of the recovered impulse responses by about 20 dB and resulted in a normalized root-meansquare difference of 3.9% between the data sets. 1D full-waveform Occam inversions of the real data showed that Harding was detectable and its lateral extent was also reasonably well-defined. The results indicate that the multi-transient Electromagnetic Method is suitable for exploration, appraisal and monitoring hydrocarbon production.