Azimuth Information Research Articles

Design and Application of a Series and Parallel-summation Logarithmic Video Amplifier

Starting with the concept of logarithmic video amplifier, this paper mainly derives the transfer functions of different logarithmic video amplifiers. The practical application of logarithmic video amplifier in the radar warning receiver is designed, and three pieces of conclusion about logarithmic video amplifier in RWR have been reached. Firstly, logarithmic transformation is completed for obtaining the azimuth information. Secondly, compressing the dynamic range is realized so that to the subsequent circuits signal processing becomes easier. Thirdly, the signal is amplified for improving the sensitivity of the receiver. A three-parallel-summation and single-series logarithmic video amplifier is used in a RWR so its direction finding precision is up to 8°, its dynamic range is up to 140dB, its sensitivity is up to -80dBm and its technique is in a higher level.

On the depth of detection of logging-while-drilling resistivity measurements for looking-around and looking-ahead applications

The depth of detection (DOD), which is an important concept in logging data interpretation, describes the detection capability of the borehole measurements. We have extended the definition of DOD for azimuthal information, namely, the geosignal delivered by azimuthal resistivity tools, to resistivity logs in logging-while-drilling (LWD) applications. Instead of using the radial geometric factor, the detection thresholds in predicting a geologic boundary are used to describe the DOD of a measurement. This definition unifies the criteria to evaluate the detectability of different borehole measurements, such as LWD resistivity measurements and geosignals. It also can be generalized to other kinds of well logging methods in LWD applications. Using the proposed definition, we analyze the detection capability of the LWD resistivity measurements in looking-around and looking-ahead applications; they provide more tangible descriptions. In vertical or near-vertical wells, the definition provides an indicator to evaluate the capability and reliability of looking ahead of deep/ultradeep LWD resistivity tools. The investigations on the influence of the DOD on the distance-to-boundary inversion, which can help in developing a robust and accurate inversion scheme, also are presented and discussed.

Foreign Object Intrusion Detection on Metro Track Using Commodity WiFi Devices with the Fast Phase Calibration Algorithm.

With continuous development in the scales of cities, the role of the metro in urban transportation is becoming more and more important. When running at a high speed, the safety of the train in the tunnel is significantly affected by any foreign objects. To address this problem, we propose a foreign object intrusion detection method based on WiFi technology, which uses radio frequency (RF) signals to sense environmental changes and is suitable for lightless tunnel environments. Firstly, based on extensive experiments, the abnormal phase offset between the RF chains of the WiFi network card and its offset law was observed. Based on this observation, a fast phase calibration method is proposed. This method only needs the azimuth information between the transmitter and the receiver to calibrate the the phase offset rapidly through the compensation of the channel state information (CSI) data. The time complexity of the algorithm is lower than the existing algorithm. Secondly, a method combining the MUSIC algorithm and static clutter suppression is proposed. This method utilizes the incoherence of the dynamic reflection signal to improve the efficiency of foreign object detection and localization in the tunnel with a strong multipath effect. Finally, experiments were conducted using Intel 5300 NIC in the indoor environment that was close to the tunnel environment. The performance of the detection probability and localization accuracy of the proposed method is tested.

Specifying advantages of multi-modal cueing: Quantifying improvements with augmented tactile information

This work examines how tactile cues, encoded with azimuth and distance information, compare with visual and speech cues on performance and mental workload in a target detection task. Two experiments are reported using a simulated environment in which targets were presented at varying azimuth and distance locations. In the first experiment, participants engaged targets both while stationary and while in motion using tactile, visual, or speech cues. A no cueing control was included. In the second multi-modal experiment, participants completed the same task using cue pairings. Performance metrics consisted of hits, misses due to non-detection, misses due to inaccurate engagement, false alarms, response time, navigation errors as well as subjective ratings of mental workload scores were also collected. Results demonstrate the superiority of tactile cues as a means to communicate target location information either as a single modality or when paired with the two other cue types.

Inside-out azimuthally selective NMR tool using array coil and capacitive decoupling

Inside-out nuclear magnetic resonance (NMR) is a unique technique for investigating large in-situ objects outside of tools, to provide pore structure and pore-bearing fluids properties. However, in borehole, objects towards azimuthal orientations pose different properties, referred to as azimuthal spatial heterogeneity. This may lead to ambiguous evaluations by utilizing present inside-out NMR measurement, which hardly resolves azimuthal information and loses the location information of oil/gas. In this paper, we for the first time design and construct an innovative tool to investigate the heterogeneity of large in-situ samples. The most key component, array coil, which performs with azimuthal selection, measurement consistency and interactive isolation, configured in this novel tool to capture heterogeneity information. Whereas, strong coupling between neighboring coil elements largely decrease the coil sensitivity. Capacitive decoupling network is bridged into adjacent ports without segmenting coils to be decoupled and could be easily adjusted by electrical relays. The coil model and numerical simulation are firstly given to demonstrate the array coil configuration, B1 field map and mutual coupling effects on coil sensitivity. Capacitive network is then introduced to be theoretically and practically analyzed to minimize coupling effects. Simulation and experimental results demonstrate that these coil elements have excellent consistency and independence to feasibly acquire the azimuthal NMR data.

Robust Azimuth Measurement Method Based on Polarimetric Imaging for Bionic Polarization Navigation

Azimuth information obtained from a polarization pattern in the sky provides many organisms like insects and birds, with the ability to navigate. The aim of this article is to investigate the azimuth method to measure the solar meridian from the pattern of the Angle of E (AOE) vector when it is partially obscured and disturbed. The model of the sky polarization pattern projected onto an imaging sensor is analyzed. The projection characteristic of the solar meridian is proved to be a straight line passing through the principal point, which is composed of pixels with the E-vector orientation 90° in the AOE map. Based on the mutation feature of the gradient amplitude of E-vector orientation 90° and occlusion without mutation on the solar meridian, a robust gradient amplitude and binary integration (GABI) azimuth method for a polarization imaging sensor is proposed. Then, the feasibility and robustness of this method are verified via numerical simulation and outdoor experiments, and the results show that when branches and buildings shield more than 80% of the AOE map, the azimuth measurement method remains effective. The accuracy of azimuth is 0.417° ( $\sigma$ ). This indicates that the azimuth can be effectively measured, even in the presence of occlusion and interference.

Experiment of 3D Seismic Reflection Technique for Forward Probing on TBM Tunnel Face

Geophysical technologies are used to mitigate geological hazard caused by adverse geological conditions in front of a tunnel face. The prevailing method for forward probing for tunnels constructed by a tunnel boring machine (TBM) for advance prediction is based on seismic detection. Conventional tunnel seismic prediction technology uses P- and S-waves with sources fired on the tunnel wall or face and layout receivers on the tunnel wall to acquire the reflected waves. However, the results show that most of these methods have different deficiencies that are in either low detection accuracy, short detection depth, and/or multiplicity in imaging. This paper proposes a new high resolution tunnel advance prediction technology on the face based on 3D seismic wave detection. It arranges the 3D high-density source and recording geometry on the tunnel face to receive reflected P-waves for 3D imaging. By using the 3D numerical simulation, we first analyze the energy distribution and propagation characteristics of the wave field, which proves that our method is feasible. Compared with the conventional technologies, the seismic energy propagating towards the tunnel face is stronger and produces rich reflected information. The reflected wave has the advantages of bandwidth, strong energy and little interferences from surface wave, so that the seismic phases are easy to be identified. On this basis, we present the high resolution true 3D prediction technology to obtain more comprehensive and abundant azimuth information. Our approach is further validated by an application experiment in a real-world engineering project of water conveyance tunnel. The results show that the new technique has a greater detection length, higher detection accuracy and more reliable imaging results.

Mixed near field and far field sources localization algorithm based on MEMS vector hydrophone array

A mixed near and far field sources localization algorithm is proposed which applied to the uniform linear MEMS vector hydrophone array. The algorithm includes three steps: firstly, the steering vector contains common azimuthal information in both near and far field, direction-of-arrival (DOA) can be obtained by using the MUSIC algorithm. Secondly, the direction vector array is decomposed into different matrices and DOA and range are separated efficiently. All DOAs can be obtained through searching for a feature matrix. Thirdly, one-dimensional spectrum search in Fresnel zone is carried out to realize the accurate estimation of range in near-field. Finally, the performance of the algorithm was simulated. The results verify that the proposed algorithm can achieve DOA estimation within the range of [0:2*π] and solve the problem of port and starboard ambiguity. The vector matrix algorithm does not require construction the high-order cumulants and multi-dimensional search, and can avoid parameter matching procedure.

Monitoring microstructural evolution in-situ during cyclic loading with high-resolution reciprocal space mapping

High-resolution reciprocal space mapping using high-energy hard x-rays has been developed to investigate the microstructure of grains located in the bulk of a metallic sample in a non-destructive way in-situ during different loading conditions. The technique allows to identify and follow individual grains and subgrains during ongoing deformation such as loading in tension and compression, during repeated cyclic deformation or even individual load cycles while simultaneously monitoring macroscopic stress and strain. Insight in the structural reorganization within single grains is gained by in-situ monitoring of the characteristic intensity distribution of Bragg reflections from individual grains during cyclic deformation of commercially pure polycrystalline aluminium. By reciprocal space mapping with high angular resolution and combined analysis of the radial and azimuthal information, individual subgrains are tracked during single load cycles with different strain amplitudes. Additionally, changes in mean peak position, peak width and asymmetry of integrated radial profiles from individual grains are analyzed as well as their orientation spread. In this manner, the microstructural evolution in grains embedded in the bulk of polycrystalline specimens is traced and linked to the changing mechanical loads during cyclic deformation.

DEVELOPMENT OF GPS SATELLITE VISIBILITY SIMULATION METHOD UNDER URBAN CANYON ENVIRONMENT

Abstract. When the UAV is flying in a lower area than the buildings in the urban environment, the GPS positioning accuracy of the aircraft reduced due to the blocked or reflected signals. Therefore, when the UAVs fly in this area, it should be able to provide a criterion that can give warning message to the UAV users such as stop the auto-flight mode or not rely too much on the position of the UAV represented on the monitor of GCS. In this study, the Elevation Mask Profile (EMP) generation algorithm proposed which calculates azimuth and elevation angle ranges blocked by obstacles at certain grid points by using DSM. It is a core algorithm for a GPS simulator developed that predict the blocked satellite signal by matching the EMP calculated for each grid point with the GPS satellites' azimuth and elevation angle information at the grid point. According to the comparison of EMP and observed data, most of the results had correlation with obstacles nearby. We found some signal blocking areas were not determined as EMP due to the skyscrapers located out of the target area where DSM was constructed. To overcome this limitation, larger spatial data than the DSM that used in this study must be applied. Furthermore, additional studies about optimal search radius definition in EMP calculation procedure to acquire more accurate and standardized EMP are necessary.

Advancement of Individualized Head-Related Transfer Functions (HRTFs) in Perceiving the Spatialization Cues: Case Study for an Integrated HRTF Individualization Method

Head-related transfer function (HRTF), which varies across individuals at the same direction, has grabbed widespread attention in the field of acoustics and been used in many scenarios. In order to in-depth investigate the performance of individualized HRTFs on perceiving the spatialization cues, this study presents an integrated algorithm to obtain individualized HRTFs, and explores the advancement of such individualized HRTFs in perceiving the spatialization cues through two different binaural experiments. An integrated method for HRTF individualization on the use of Principle Component Analysis (PCA), Multiple Linear Regression (MLR) and Partial Least Square Regression (PLSR) was presented first. The objective evaluation was then made to verify the algorithmic effectiveness of that method. Next, two subjective experiments were conducted to explore the advancement of individualized HRTFs in perceiving the spatialization cues. One was auditory directional discrimination degree based on semantic differential method, in which the azimuth information of sound sources was told to the listeners before listening. The other was auditory localization, in which the azimuth information was not told to the listeners before listening. The corresponding statistical analyses for the subjective experimental results were made. All the experimental results support that individualized HRTFs obtained from the presented method achieve a preferable performance in perceiving the spatialization cues.

Design of an Innovative Downhole NMR Scanning Probe

Currently, commercial downhole nuclear magnetic resonance (NMR) tools can measure depth (along with borehole axis) and radial (perpendicular with borehole axis) profile information simultaneously. However, in many cases, the lack of information due to the strong heterogeneity, partial invasion of the drilling mud around the borehole or borehole collapse will have a serious impact on applications. In order to ensure the validity of each measurement, acquisition of azimuthal information is as important as the depth and radial profile information. In this paper, we described the performance and response simulation of an innovative centralized downhole NMR scanning probe (SMRT). This probe uses hollow cylinder magnets as main magnets to produce azimuthally symmetrical polarized (related to the $z$ -axis) static magnetic field ${B} _{0}$ . Circular focusing magnets and high permeability materials are added between the main magnets to simultaneously adjust the field homogeneity along with $z$ -axis, increase the height of sensitive region and enhance the strength of ${B} _{0}$ field in sensitive region. Coil array is composed of eight independent coil units with the same performance but different azimuthal selection function used to scan the formation around the probe so that eight azimuthally distinguishable sensitive regions can be investigated. Magnets and coil array configuration are optimized with the finite-element method, and ${B} _{0}$ field and ${B} _{1}$ field is calculated to obtain the spin dynamic response. Numerical simulation results show that NMR signals from different azimuthal sections had no overlapped feature (sensitive volume of each azimuthal direction is thin shell of arc length approximate 45°) and high azimuthal resolution is feasible.

An improved aerial target detection algorithm

This paper considers aerial target detection using an improved remote sensing method. The background is removed which can cause a lower signal to noise ratio (SNR) of the radio frequency (RF) signal. The singular value decomposition technique is used to extract the major components of RF signal. To enhance RF signal, the automatic gain control method is employed. The maximum slope and standard deviation are used to analyze the characteristic to provide two results for aerial target detection including the azimuth information and bandwidth. These estimates are used to determine if a target is present in the detection environment. The experimental results validate the effectiveness and better capability of the proposed detection method.

Can fracture orientation and intensity be detected from seismic data? Woodford Formation, Anadarko Basin, Oklahoma investigation

With readily available wide-azimuth, onshore, 3D seismic data, the search for attributes utilizing the azimuthal information is ongoing. Theoretically, in the presence of ordered fracturing, the seismic wavefront shape changes from spherical to nonspherical with the propagation velocity being faster parallel to the fracturing and slower perpendicular to the fracture direction. This concept has been adopted and is used to map fracture direction and density within unconventional reservoirs. More specifically, azimuthal variations in normal moveout velocity or migration velocity are often used to infer natural fracture orientation. Analyses of recent results have called into question whether azimuthal velocity linked to intrinsic azimuthal velocity variations can actually be detected from seismic data. By use of 3D orthorhombic anisotropic elastic simulation, we test whether fracture orientation and intensity can be detected from seismic data. We construct two subsurface models based on interpreted subsurface layer structure of the Anadarko Basin in Oklahoma. For the first model, the material parameters in the layers are constant vertically transverse isotropic (VTI) in all intervals. The second model was constructed the same way as the base model for all layers above the Woodford Shale Formation. For the shale layer, orthorhombic properties were introduced. In addition, a thicker wedge layer was added below the shale layer. Using the constructed model, synthetic seismic data were produced by means of 3D anisotropic elastic simulation resulting in two data sets: VTI and orthorhombic. The simulated data set was depth migrated using the VTI subsurface model. After migration, the residual moveouts on the migrated gathers were analyzed. The analysis of the depth-migrated model data indicates that for the typical layer thicknesses of the Woodford Shale layer in the Anadarko Basin, observed and modeled percentage of anisotropy and target depth, the effect of intrinsic anisotropy is too small to be detected in real seismic data.

Biological Eagle-Eye-Based Visual Platform for Target Detection

In this paper, the systematic design and implementation of a biological eagle-eye-based visual platform is presented for target detection. Inspired by the structure and properties of the eagle eye, the hardware configuration of the visual platform is presented, and software programs including image stitching and target detection are developed. The saliency analysis method is adopted to estimate the position of the potential target. The optical triangulation is utilized to obtain the relative azimuth information of the estimated target. Comparative experimental results show that the overall platform is efficient at target detection.

Modulation of the High-Order Laguerre-Gaussian Beam in Dressing Four-Wave Mixing

We report an experiment about the transformation of radical and azimuthal information of high-order Laguerre-Gaussian beam from the probe beam to dressing four-wave mixing beam. During this process, dressing Kerr nonlinear dispersion causes a spatial splitting on output Laguerre-Gaussian beam. We found that the number of split spots can be controlled by frequency detuning and power of the dressing field. The potential application of such modulated spatial splitting phenomenon on optical switching of the multi-channel router in atomic ensembles is discussed.

Short-range azimuth measurement method based on the adaptive filtering mechanism using laser and magnetism.

In order to accurately measure the target position in the short range, this paper presents a measurement method based on the laser and magnetism composite (L-M) mechanism. A single-beam pulsed laser is used to measure the target distance dynamically. The magnetic sensor is used to acquire the scanning period signal, and the azimuth information is calculated by the L-M signal. A variable step-size least mean square algorithm with a step memory effect is designed to reduce the interference. The numerical simulation and experimental results show that the method of azimuth measurement has a good measurement accuracy and anti-interference. In addition, this short-range azimuth measurement has a great potential in small moving bodies.

Seeker-Azimuth Determination with Gyro Rotor and Optoelectronic Sensors.

This paper presents an approach to seeker-azimuth determination using the gyro rotor and optoelectronic sensors. In the proposed method, the gyro rotor is designed with a set of black and white right spherical triangle patterns on its surface. Two pairs of optoelectronic sensors are located symmetrically around the gyro rotor. When there is an azimuth, the stripe width covering the black and white patterns changes. The optoelectronic sensors then capture the reflected optical signals from the different black and white pattern stripes on the gyro rotor and produce the duty ratio signal. The functional relationship between the measured duty ratio and the azimuth information is numerically derived, and, based on this relationship, the azimuth is determined from the measured duty ratio. Experimental results show that the proposed approach produces a large azimuth range and high measurement accuracy with the linearity error of less than 0.005.

Detection method of obstacle for plant protection UAV based on structured light vision

To solve the obstacle avoidance problem in plant protection UAV in operation, especially for farmland areas, a technology based on structured light vision was proposed. Based on the laser triangulation principle, through the special optical path design between the semiconductor laser and CCD sensor, an optical detection system to detect front obstacle information was designed. The line structured light emitted by the laser was reflected by the surface of the obstacle and was imaged on the CCD target surface. Through the image acquisition, processing and calculation, the distance, azimuth, width and other parameter information of front obstacle were extracted. Experiments show that this method can effectively detect the distance, azimuth and width of the obstacle in the unknown environment. The deviation of distance detection is less than 0.06 m.

Performance analysis of matched field processing localization with various line array configurations based on normal mode decomposition

Various line array configurations are evaluated for the source localization performance based on the analysis of mode decomposition matrix in this paper. The guideline of array shape design focuses on improving the localization performance of matched filed processing, meanwhile reducing the difficulty of deploying equipment in practical experiments. In the shallow water environment, when the environment is well known, the source localization result can be obtained by matched field processing algorithms effectively, but the source localization performance is affected by the array parameters, such as array length, the number of sensors, and the configurations of various horizontal and vertical line arrays. The modal decomposition method provides a useful insight into the questions of how many modes are needed and how to design the array to resolve the modes. Therefore, the method of utilizing a normal mode acoustic propagation model to decompose mode is proposed by vertical line array, horizontal line array and combined array respectively. Then we can evaluate the source localization performance of various line array configurations by studying the characteristic of normal mode decomposition matrix, thus establishing a qualitative or even quantitative relationship between each other. The more the normal mode decomposition matrix tends to be diagonalized, the better performance of line array localization will be obtained. Simulation results show that the localization performance of matched field processing with the combined arrays will be severely degraded when the mode amplitudes cannot be accurately deduced by one of the sub-arrays. Considering the requirements for the practical experiments and various environments, the source localization performance of short vertical line array and combined array are mainly discussed in this paper. The combined array can increase the azimuth and depth information of the source and realize three-dimensional target detection while the vertical array provides range-depth information and the horizontal array provides bearing information. Simulation result indicates that the design guidelines based on the normal mode decomposition are appropriate for arrays employed for matched filed processing. Meanwhile, the combined arrays perform better than the short vertical array, which is benefited by the horizontal array's suppressing the side lobes, which leads the ratio of peak to sidelobe to increase, and thus improving the location accuracy. The values of localization accuracy of combined arrays are all above 90% according to the simulation experiment. Take the practical application into account, the combined array is undoubtedly a compromise choice for the localization performance and the test complexity.