Azimuthal Measurements Research Articles

Short-range azimuth measurement method based on single-pulse laser beam expanding mechanism

Short-range azimuth measurement method based on single-pulse laser beam expanding mechanism

Ultrafast Time-Domain Spectroscopy Reveals Coherent Vibronic Couplings upon Electronic Excitation in Crystalline Organic Thin Films.

The coherent coupling between electronic excitations and vibrational modes of molecules largely affects the optical and charge transport properties of organic semiconductors and molecular solids. To analyze these couplings by means of ultrafast spectroscopy, highly ordered crystalline films with large domains are particularly suitable because the domains can be addressed individually, hence allowing azimuthal polarization-resolved measurements. Impressive examples of this are highly ordered crystalline thin films of perfluoropentacene (PFP) molecules, which adopt different molecular orientations on different alkali halide substrates. Here, we report polarization-resolved time-domain vibrational spectroscopy with 10 fs time resolution and Raman spectroscopy of crystalline PFP thin films grown on NaF(100) and KCl(100) substrates. Coherent oscillations in the time-resolved spectra reveal vibronic coupling to a high-frequency, 25 fs, in-plane deformation mode that is insensitive to the optical polarization, while the coupling to a lower-frequency, 85 fs, out-of-plane ring bending mode depends significantly on the crystalline and molecular orientation. Comparison with calculated Raman spectra of isolated PFP molecules in vacuo supports this interpretation and indicates a dominant role of solid-state effects in the vibronic properties of these materials. Our results represent a first step toward uncovering the role of anisotropic vibronic couplings for singlet fission processes in crystalline molecular thin films.

Devising an analytical method for estimating aircraft positioning accuracy by an infocommunication network of optoelectronic stations

The object of this study is the monitoring processes of airspace in the visible and infrared frequency ranges using an infocommunication network of optoelectronic tracking stations. The problem addressed is the assessment of accuracy in positioning aerial vehicles in airspace, considering random and systematic errors in video surveillance. The proposed method allows for the analytical evaluation of variance in the coordinates of aerial vehicles in airspace at any given moment, depending on the variance in errors from all components of the video surveillance process. The following results are reported: – mathematical models for both open and covert video surveillance by the infocommunication network of optoelectronic stations based on the trajectories of aerial vehicles, which enable the estimation of their coordinates for each moment of video surveillance. – analytical relationships between the variance of geolocation of aerial vehicles and the variance of errors in all components of the video surveillance process. A key feature of the method is its practical independence on the type and size of aerial vehicles. The method requires the availability of metrological characteristics of the optoelectronic station instruments and synchronized measurements of azimuth, elevation angle (for covert), and slant range (for open video surveillance). The numerical values of the root mean square deviations of the positioning errors of aerial vehicles under various video surveillance conditions range from 0.1 to 0.35 meters, confirming the effectiveness of using the infocommunication network of optoelectronic stations as an instrumental tool for high-precision trajectory measurements.

Estimation of Isotropic Pathloss From Directional Channel Measurements in Azimuth and Elevation

Estimation of Isotropic Pathloss From Directional Channel Measurements in Azimuth and Elevation

Object azimuth measurement based on optical orbital angular momentum phase spectrum under tilted irradiation condition

In optical remote sensing, a beam carrying orbital angular momentum can be used to identify the azimuth of an object. However, most of the studies reported currently require the beam to be illuminated vertically to the surface of the object, and the general case of tilted irradiation for the beam has not been fully discussed. In this paper, an object azimuth measurement method based on orbital angular momentum phase spectrum under tilted irradiation condition is proposed. We analyze the relationship between the measurement error caused by the beam oblique irradiation and the angle of tilt and propose an error compensation method. In the experiment, the orbital angular momentum phase spectrum of the Laguerre-Gaussian beam is obtained by a four-step phase-shifting method, and the error caused by tilt modulation is measured. After implementing the error compensation scheme, the maximum absolute error in azimuth measurement under tilted irradiation conditions is maintained within 2.15°. Across all tilt angles, the average absolute error remains below 0.73°. The method proposed in this paper has a certain reference value for expanding the practical application of orbital angular momentum beams in the field of remote sensing.

IMU/Magnetometer-Based Azimuth Estimation with Norm Constraint Filtering.

A typical magnetometer-based measurement-while-drilling (MWD) system determines the azimuth of the bottom hole assembly during the drilling process by employing triaxial accelerometers and magnetometers. The geomagnetic azimuth solution is susceptible to magnetic interference, especially strong magnetic interference and so a rotary norm constraint filtering (RNCF) method for azimuth estimation, designed to support a gyroscope-aided magnetometer-based MWD system, is proposed. First, a new magnetic dynamical system, one whose output is observed by the magnetometers triad, is designed based on the Coriolis equation of the desired geomagnetic vector. Second, given that the norm of the non-interfered geomagnetic vector can be approximated as a constant during a short-term drilling process, a norm constraint procedure is introduced to the Kalman filter. This is achieved by the normalization of the geomagnetic part of the state vector of the dynamical system and is undertaken in order to obtain a precise geomagnetic component. Simulation and actual drilling experiments show that the proposed RNCF method can effectively improve the azimuth measurement precision with 98.5% over the typical geomagnetic solution and 37.1% over the KF in a RMSE sense when being strong magnetic interference environment.

A Novel Rain Identification and Rain Intensity Classification Method for the CFOSAT Scatterometer

A Novel Rain Identification and Rain Intensity Classification Method for the CFOSAT Scatterometer

An Underwater Source Localization Method Using Bearing Measurements.

Angle-of-arrival (AOA) measurements are often used in underwater acoustical localization. Different from the traditional AOA model based on azimuth and elevation measurements, the AOA model studied in this paper uses bearing measurements. It is also often used in the Ultra-Short Baseline system (USBL). However, traditional acoustical localization needs additional range information. If the range information is unavailable, the closed-form solution is difficult to obtain only with bearing measurements. Thus, a localization closed-form solution using only bearing measurements is explored in this article. A pseudo-linear measurement model between the source position and the bearing measurements is derived, and considering the nonlinear relationship of the parameters, a weighted least-squares optimization equation based on multiple constraints is established. Different from the traditional two-step least-squares method, the semidefinite programming (SDP) method is designed to obtain the initial solution, and then a bias compensation method is proposed to further minimize localization errors based on the SDP result. Numerical simulations show that the performance of the proposed method can achieve Cramer-Rao lower bound (CRLB) accuracy. The field test also proves that the proposed method can locate the source position without range measurements and obtain the highest positioning accuracy.

Mueller matrix polarization interferometry of optically anisotropic architectonics of biological tissue object fields: the fundamental and applied aspects

The presented results concern the diagnostic application of vector-parameter polarization mapping and polarization-interference phase scanning applied to layered azimuths and ellipticity polarization maps obtained with the help of digital holographic reproduction for phase-inhomogeneous tissue layers in the female reproductive system. The differential diagnosis of the pathological changes in optically anisotropic polycrystalline tissue components, specifically “benign (fibroids) and precancerous (endometriosis),” was investigated. All studies within the representative groups of the histological samples were conducted using circularly polarized laser radiation, ensuring azimuthal invariance and polarization measurement reliability. Integral and layered maps and polarization azimuths and ellipticity random variable distribution histograms were obtained from the microscopic images of histological sections from the female reproductive system tumors. Systematized tables present statistical moments which characterize azimuths and ellipticity polarization maps for fibroids and endometriosis tissues. It is shown that the statistical parameters (diagnostic markers) are the most sensitive to benign and precancerous changes in the female reproductive system tissues. The results of information analysis, including the accuracy determination of the diagnostic vector-parameter polarization and polarization-interference methods for detecting and differentiating the samples of fibroids and precancerous endometriosis tissues in the female reproductive system, are presented.

Adaptive Global Optimization of Real-Time Boundary Detection From the LWD Azimuthal Electromagnetic Measurements in Layered TI Formation With Arbitrarily Deviated Borehole

Adaptive Global Optimization of Real-Time Boundary Detection From the LWD Azimuthal Electromagnetic Measurements in Layered TI Formation With Arbitrarily Deviated Borehole

ACCURACY ANALYSIS OF AIRCRAFT POSITIONING USING NAVIGATIONAL DATA FROM AVIA-W RADAR

The paper presents an analysis of the accuracy of determination of parameters of the position of aircraft using data from the AVIA-W radar. In the first place, the authors determined the position of the aircraft as well as the range and azimuth parameters by the AVIA-W radar, located in Dęblin. This was followed by a determination of the absolute position error of the aircraft and the determination of the range and azimuth measurement error by the AVIA-W radar. The research test was carried out using a Diamond DA40 NG aircraft on which a GPS satellite receiver was mounted in order to determine the flight reference position. In addition, the range and azimuth measurements for the aircraft were acquired from the AVIA-W radar. Navigational calculations were conducted for polar and rectangular planar coordinates. Based on the performed research, the azimuth error was found to be –1.4o, while the radar range measurement error was equal to –0.04 km. The conducted research is experimental in its character. In the future it will be repeated and extended to the GCA-2000 radar, which is also located at Dęblin military airfield.

A novel efficient estimator for three‐dimensional bearings‐only source localisation with unknown sensor altitude and systematic measurement errors

AbstractA novel two‐stage profile maximum likelihood estimator is proposed to estimate the source location and the systematic errors jointly, with the aim of addressing the problem of source localisation using angle‐only measurements from a single sensor with unknown sensor altitude and systematic measurement errors. The proposed two‐stage profile maximum likelihood estimator algorithm is capable of decoupling the azimuth and elevation angle measurements while transforming the original maximum likelihood optimisation problem into two sub‐problems, that is, two‐dimensional‐projected maximum likelihood estimator and relative altitude maximum likelihood estimator. In terms of the two‐dimensional‐projected maximum likelihood estimator, an algorithm combining pseudo‐linear estimating and Kalman filtering is proposed to generate an initial estimate. Subsequently, a Gauss–Newton iterative method is developed to estimate the two‐dimensional‐projected target location and the azimuth systematic error jointly. The relative height maximum likelihood estimator is initialised using a pseudo‐linear estimator. Next, a Gauss–Newton iterative algorithm is adopted to estimate the elevation systematic error and the relative height. As indicated by the result of the simulation studies, the proposed algorithm exhibits an estimation performance close to the Cramér–Rao lower bound with unknown sensor altitude and systematic measurement errors.

Systematic errors in a swept-wavelength null polarimeter for weak linear retardance measurements.

We recently developed a high speed null polarimeter [Opt. Express30, 18889 (2022)OPEXFF1094-408710.1364/OE.454193] based on passive polarization optics and a high speed wavelength swept laser source, enabling the measurement of linear retardance with 3.1µd e g/H z resolution within a minimum acquisition time of 10µs, corresponding to a linear retardation of 8.6×10-9 λ/H z. The counterpart of high sensitivity lies in the systematic errors unlike Mueller polarimeters, which can be calibrated but which are much less sensitive. This paper focuses on the accuracy of this null polarimeter and provides hardware and numerical solutions to improve both linear retardance and azimuth measurements. Experiments and theoretical simulations are carried out to demonstrate the relevancy of these solutions.

An interplay between optical rectification and transient photocurrent effect on THz pulse generation from bulk MoS2 layered crystal

Development of novel schemes for efficient terahertz (THz) generation from transition metal dichalcogenides are useful for realizing integrated THz devices based on them and also, understanding of the related fundamental processes from such studies will guide to suitable designs. Here, we report the THz emission efficiency of bulk MoS2 layered crystal at varying femtosecond excitation wavelengths, from 550 nm to the telecommunication wavelength of 1550 nm. By using both the below bandgap excitation at longer wavelengths and the above bandgap excitation at shorter wavelengths, we resolve THz emission contributions from resonant and non-resonant optical rectification (OR) processes, and the surface field induced transient photocurrent effect (TPE). A relatively much larger contribution to THz emission from the TPE than the resonant OR is measured for the above bandgap excitation. We have measured a clear difference between the resonant and nonresonant OR processes. The pure OR part is exclusively determined from detailed experiments using excitation intensity, polarization angle, and azimuthal angle dependent measurements. For the above bandgap excitation, the THz emission gets highly saturated with the increasing excitation intensity. Also, the value of the saturation intensity increases (decreases) with the excitation photon energy (wavelength). Interestingly, we find that the linear polarization angle and the azimuthal angle dependent THz signal due to resonant OR is π/2 phase offset relative to that due to the nonresonant OR.

Role of initial conditions in plasma-current coupling of gas-puff Z-pinches

Azimuthal magnetic field measurements obtained during the implosion phase of an oxygen gas-puff Z-pinch on a 500 kA peak current and 180 ns rise time linear transformer driver are presented. While a fraction of the driver current was measured within the imploding plasma, key initial conditions were found to significantly impact the delivery of current to the plasma load. The electrode geometry was modified to assist the initial dielectric breakdown and resulted in improved shot reproducibility. Optimization of the gas injection plenum pressure and timing resulted in an increase in the current coupling parameter, defined as the ratio of the measured value of Bθ to the expected value, from 50% to 75%. The degree of radial expansion of the gas puff in the load region, which is suspected to lead to the observed current loss during the implosion, was reduced by shortening the valve opening duration. Additionally, a pre-embedded axial magnetic field of up to 0.2 T was found to have no significant impact on the plasma-current coupling of the oxygen implosions.

A Study on a Novel Inverted Ultra-Short Baseline Positioning System and Phase Difference Estimation

Autonomous underwater vehicles (AUVs) are important tools for exploring and studying the ocean. To improve the stealthiness of AUV positioning, a new type of inverted ultra-short baseline (i-USBL) positioning system is proposed in this paper. The system uses a surface GPS buoy as a positioning base station to transmit positioning signals to the AUV, which receives the signals through the i-USBL and calculates its own coordinates. In this way, the power consumption of the AUV will be lower, improving its endurance. In addition, azimuth observation is one of the key observation quantities in ultra-short baseline positioning systems. Therefore, this paper derives two phase difference estimation algorithms for azimuth measurement, which are the Least Mean Square (LMS) algorithm and the Discrete Fourier Transform (DFT) algorithm. Simulation results show that when the signal-to-noise ratio (SNR) is less than or equal to 0 dB, the DFT algorithm has higher accuracy; when SNR is greater than or equal to 10 dB, LMS has slightly higher accuracy than DFT; however, DFT is more stable than LMS at all SNRs. When SNR is 20 dB, the maximum azimuth measurement error of LMS and DFT is 0.3301° and 0.2204°, respectively, which can meet the positioning accuracy requirements. The average running times of LMS and DFT are 0.085 s and 0.011 s, respectively, and LMS has a faster running speed. In summary, the LMS algorithm can be used for azimuth observation when the SNR is good, and DFT can be applied when the SNR is poor.

3D generalized bias compensated pseudolinear Kalman filter for colored noisy bearings-only measurements

Bias compensated pseudolinear Kalman filter (BC-PLKF) degrades for bearings-only tracking if measurements are corrupted with time-correlated noises. Generalized bias compensated pseudolinear Kalman filter (GBC-PLKF), on the other hand, outperforms BC-PLKF and many other comparison filters for two-dimensional (2D) cases under colored noise. However, GBC-PLKF is not practicable for three-dimensional (3D) real-life problems and due to the coupling between lateral and longitudinal planes, its 3D extension is not trivial. In this paper, bias analysis of 3D pseudolinear Kalman filter (PLKF) with azimuth and elevation measurements including colored noise is performed. Then, the low-cost recursive filter, 3D-GBC-PLKF is proposed for 3D real-life applications. The performance and effectiveness of the proposed algorithm is demonstrated with an air-to-surface guided missile pursuing a typical target.

Evolution of electromagnetic logging while drilling tools (based on national and foreign literature)

Important stages in the development of electromagnetic logging tools based on national and foreign literature are considered: adaptation of traditional tools to logging while drilling and modification of tools for logging while drilling in order to provide the possibility of carrying out deeper and azimuthal measurements. Applied algorithms for modeling and interpreting data are briefly described, examples of tools which are used while drilling oil wells, including the national tool, are given.

Estimate of Secondary Porosity from Surface Crossed Square Array Resistivity Measurements

The secondary porosity of rocks and formations plays an important role in water exploration and exploitation in crystalline rocks. Furthermore, cracks and voids are paths for contaminated fluid propagation and, thus, their location can be very important in environmental studies. Usually, secondary porosity is estimated from well logging observations, but some previous works have pointed out that azimuthal resistivity measurements and the square array can be used to estimate this parameter. Herein, the use of the square array and of the crossed square array will be investigated to estimate the secondary porosity. Thus, the analogue model and field resistivity data obtained with those arrays are discussed and interpreted. The analogue model simulates contacts between the isotropic and anisotropic media and between two different anisotropic media. The field data are from an area where steeply dipping formations prevail and contacts between the isotropic and anisotropic media are present. The calculated secondary porosity values are compared with the lateral changes in the resistivity and anisotropy, and pseudo sections are shown to aid the interpretation. In addition, 2D resistivity models for the field survey are produced to provide a better image and interpretation of the data. The overall results and limitations are discussed, and data acquisition procedures are proposed to optimize the field work.

Interface-resolved study of magnetism in MgO/FeCoB/MgO trilayers using x-ray standing wave techniques

Interfaces in the MgO-FeCoB-MgO trilayer have been studied with grazing incident nuclear resonance scattering (GINRS) using the x-ray standing waves (XSW) technique. High depth selectivity of the present method allows one to measure magnetism and structure at the two interfaces of FeCoB, namely, FeCoB-on-MgO and MgO-on-FeCoB, independently, yielding an intriguing result that both interfaces are not symmetric. A high-density layer with an increased magnetic hyperfine field at the FeCoB-on-MgO interface suggests different growth mechanisms at the two interfaces. The azimuthal angle-dependent magneto-optic Kerr effect measurements reveal the presence of unusual uniaxial magnetic anisotropy (UMA) in the trilayer. An in-situ temperature-dependent study discovered that this UMA systematically reduces with temperature. The trilayer becomes isotropic at 450C with an order-of-magnitude increase in coercivity. The asymmetry at the interfaces is, in turn, explained by boron diffusion from the FeCoB interface layer into the nearby MgO layer. Stress-induced UMA is observed in the boron-deficient FeCoB layer, superimposed with the bulk FeCoB layer, and found to be responsible for unusual UMA. The temperature-dependent variation in the UMA and coercivity can be understood in terms of variations in the internal stresses and coupling between FeCoB bulk and the interface layer.