Angular Response Research Articles

Exploiting the Potential of Urban DAS Grids: Ambient-Noise Subsurface Imaging Using Joint Rayleigh and Love Waves

Abstract Distributed acoustic sensing (DAS) data become important for seismic monitoring of subsurface structures in urban areas. Different from the previous studies that only focused on Rayleigh waves, we report successful observation and analysis of both Rayleigh and Love waves extracted from ambient-noise interferometry, using orthogonal segments of fiber-optic cables in San Jose, California. Theoretical angular responses of DAS ambient-noise cross correlation, together with numerical experiments, help identify DAS channel pairs expected to record stronger Love waves than Rayleigh waves. Based on these waveforms, we further obtain clear Rayleigh- and Love-wave dispersion maps, including both phase and group velocities, with various channel pair orientations. Finally, we perform a joint inversion of Rayleigh- and Love-wave dispersion curves to obtain depth-dependent subsurface velocity structures of the top 100 m. Our inversion result is consistent with the model from the previous study based on Rayleigh-wave dispersion and horizontal-to-vertical spectral ratio. In addition, the joint inversion of Love and Rayleigh is more robust than that of the independent inversion of either type of wave. Our new study demonstrates the potential of surface-wave analysis on fiber-optic cables with complex geometry, which can further advance the seismic monitoring of urban areas.

Evaluation of 2D ion chamber arrays for patient specific quality assurance using a static phantom at a 0.35 T MR-Linac

IntroductionPatient specific quality assurance (QA) in MR-Linacs can be performed with MR-compatible ion chamber arrays. However, the presence of a static magnetic field can alter the angular response of such arrays substantially. This works investigates the suitability of two ion chamber arrays, an air-filled and a liquid-filled array, for patient specific QA at a 0.35 T MR-Linac using a static phantom. MethodsIn order to study the angular response, the two arrays were placed in a static, solid phantom and irradiated with 9.96 × 9.96 cm2 fields every 10° beam angle at a 0.35 T MR-Linac. Measurements were compared to the TPS calculated dose in terms of gamma passing rate and relative dose to the central chamber. 20 patient specific quality assurance plans were measured using the liquid-filled array. ResultsThe air-filled array showed asymmetric angular response changes of central chamber dose of up to 18% and down to local 3 mm / 3% gamma rates of 20%, while only minor differences within 3% (excluding parallel irradiation and beams through the couch edges) were found for the liquid-filled ion chamber array without rotating the phantom. Patient plan QA using the liquid-filled array yielded a median local 3 mm / 3% 3D gamma passing rate of 99.8% (range 96.9%–100%) ConclusionA liquid-filled ionization chamber array in combination with a static phantom can be used for efficient patient specific plan QA in a single measurement set-up in a 0.35 T MR-Linac, while the air-filled ion chamber array phantom shows large angular response changes and has its limitations regarding patient specific QA measurements

Seabed Sediment Classification through Multispectral Backscatter Mosaic MBES and Angular Response Analysis

Seabed Sediment Classification through Multispectral Backscatter Mosaic MBES and Angular Response Analysis

Multitemporal Acoustic Backscatter Data Analysis to Monitor the Dynamics of Seabed Surface Sediments

Backscatter strength is a product of underwater acoustic remote sensing. This study used a multibeam echosounder as an acoustic remote sensing instrument to collect backscatter strength data. These data are then used to classify the surficial sediment distribution. To monitor the difference in seabed sediment distribution, a time-series survey was performed to obtain multitemporal acoustic backscatter data. An EM 304 multibeam system from Kongsberg was mounted on the Research Vessel Baruna Jaya III from the Indonesia National Research and Innovation Agency (BRIN). It was used to collect backscatter data in the waters of Raja Ampat, Indonesia. The data were collected at different times, April and July 2021. Geometric and radiometric corrections were applied to these backscatter data. Based on the angular response curve analysis from acoustic backscatter strength, the research area can be classified into four seabed sediment types: boulder, gravel, sand, and mud. A comparison of both time series backscatter data shows that the boulder and gravel areas increased by 13.6% and 19.0%, respectively. Elsewhere, the area with sediment types of sand and mud diminished by 30.5% and 2.0%. The change in the sediment type area occurred as much as 50.5%, while the remaining 49.5% area remained unchanged. This resulting value is apparently derived from the steep topography that rapidly changes sediment distribution. One such suggestion is that sediment sampling should be performed to confirm the model from angular response curve analysis.

Multitemporal Acoustic Backscatter Data Analysis to Monitor the Dynamics of Seabed Surface Sediments

Backscatter strength is a product of underwater acoustic remote sensing. This study used a multibeam echosounder as an acoustic remote sensing instrument to collect backscatter strength data. These data are then used to classify the surficial sediment distribution. To monitor the difference in seabed sediment distribution, a time-series survey was performed to obtain multitemporal acoustic backscatter data. An EM 304 multibeam system from Kongsberg was mounted on the Research Vessel Baruna Jaya III from the Indonesia National Research and Innovation Agency (BRIN). It was used to collect backscatter data in the waters of Raja Ampat, Indonesia. The data were collected at different times, April and July 2021. Geometric and radiometric corrections were applied to these backscatter data. Based on the angular response curve analysis from acoustic backscatter strength, the research area can be classified into four seabed sediment types: boulder, gravel, sand, and mud. A comparison of both time series backscatter data shows that the boulder and gravel areas increased by 13.6% and 19.0%, respectively. Elsewhere, the area with sediment types of sand and mud diminished by 30.5% and 2.0%. The change in the sediment type area occurred as much as 50.5%, while the remaining 49.5% area remained unchanged. This resulting value is apparently derived from the steep topography that rapidly changes sediment distribution. One such suggestion is that sediment sampling should be performed to confirm the model from angular response curve analysis.

Innovative Approach for the Determination of a DC Motor’s and Drive’s Parameters Using Evolutionary Methods and Different Measured Current and Angular Speed Responses

The determination is presented of seven parameters of a DC motor’s drive. The determination was based on a comparison between the measured and simulated current and speed responses. For the parameters’ determination, different evolutionary methods were used and compared to each other. The mathematical model presenting the DC drives model was written using two coupled differential equations, which were solved using the Runge–Kutta first-, second-, third- and fourth-order methods. The approach allows determining the parameters of controlled drives in such a way that the controller is taken into account with the measured voltage. Between the tested evolutionary methods, which were Differential Evolution with three strategies, Teaching-Learning Based Optimization and Artificial Bee Colony, the Differential Evolution (DE/rand/1/exp) can be suggested as the most appropriate for the presented problem. Measurements with different sampling times were used, and it was found out that at least some measuring points should be at the speed-up interval. Different lengths of the measured signal were tested, and it is sufficient to use a signal consisting of the drive’s acceleration and a short part of the stationary operation. The analysis showed that the procedure has good repeatability. The biggest deviation of calculated parameters considering 10 repeated measurements was 6% in case of the La calculation. The deviations of all the other parameters’ calculations were less than 2%.

Solar concentrators filled with liquid for enhancement of photocurrent generation and angular responses of light incidence

Design and manufacturing of solar concentrator materials and structures for external light trapping have been widely explored for decades to enhance solar cell performances in various photovoltaic (PV) devices such as silicon, organic, and perovskite ones. Among them, remarkable progress in development of the concentrators has been made to improve the solar concentration ratio of power conversion efficiency (PCE). However, only some studies were carried out to enhance the angular responses of light incidence (AOI). This paper reports a simple liquid-filled solar concentrator (LFSC) that can be effectively implemented by incorporating optical reflection with total internal refraction (TIR). Using the fused deposition modeling (FDM) method in the 3D printing process, the hollow compound concentrators in a parabolic shape were efficiently produced at a low cost. With liquid water and silicone oil, the simulation and experimental results illustrated that the PCE and AOI were increased for the concentrator solar cells composed of bulk heterojunction structure. In particular, it was found that all the AOI exhibited an exponential decay as a Gaussian distribution. Hence, it provided the capability of control over concentrator material and geometry in design and fabrication. In this manner, various such simple devices fabricated by the present method can be further applied in future applications such as PV cell modules and systems.

A Communication Anti-Jamming Scheme Assisted by RIS with Angular Response.

By optimizing the reconfigurable intelligent surface (RIS) reflection coefficients, the channel capacity of legitimate users can be increased, thereby enhancing the anti-jamming performance of communication systems. However, existing studies on RIS-assisted anti-jamming assume that there is no coupling between the RIS reflection coefficients and the incident angle of electromagnetic (EM) waves, which is quite unreasonable. Therefore, we consider the effect of the incident angle of EM waves on the reflection coefficients of the RIS and propose a communication anti-jamming scheme assisted by an RIS with angular response. Specifically, a problem is formulated to optimize the RIS reflection coefficients so that the legitimate signal is amplified, but the jamming signal is attenuated, thus enhancing the legitimate channel capacity. However, the coupling of the EM incident angle and the RIS reflection coefficients causes the problem to be non-convex. To tackle this problem, we equivalently transform the RIS reflection coefficients optimization problem into a quadratically constrained quadratic programming (QCQP) problem using the complex Taylor expansion and the multidimensional complex quadratic transform (MCQT) and solve it utilizing the alternating direction method of the multipliers (ADMM) algorithm. The simulation results reveal that, compared to other schemes supported by RIS without angular response, the proposed scheme is able to achieve a significant improvement in the anti-jamming performance.

Influence of eye lens dosimeter positioning in a realistic dosimetric phantom in reference radiation beams

This paper presents a novel approach to dosimeter placement evaluation for personal eye lens dosimetry. A new assembly, known as the “Eye-Band”, and an anthropomorphic phantom containing two “Real Eye Dosimeters”, referred to as REDs, are proposed. The purpose of this study is to compare the energy and angular responses of the Eye-Band dosimeter assembly with those of an anthropomorphic dosimeter holder (RED-holder) placed inside a phantom. The objective is to analyze the maximum deviations between these measurements to determine the ideal placement of the holders from a metrological point of view. The commercially available BeOSL Eye Lens Dosimeters were also used for comparison, placed near each eye. BeO OSL EzClips were used as the sensitive elements in all three holders. Overall, except for 24 keV and 33 keV at 90° incidence, the differences between the dosimeters worn on the most exposed side of the head (Eye-Band or the standard commercial casings) and the estimated dose at the most exposed lens inside the anthropomorphic phantom were less than ∼20%. Results for the energy dependence of the central Eye-Band dosimeter at each angle of incidence (0°, 30°, 60° and 90°) showed that the deviation in dose to the most exposed eye (right eye) between RED and the central Eye-Band dosimeter ranged from 0% to ∼20% across all energies and angles from 0° to 90°. These results show that the angular dependence of the dosimeter on the most exposed side of the head is critical to ensure adequate results between the doses registered by the worn dosimeters at the side or center positions and the actual dose delivered to the most exposed eye. For the least exposed eye on the exit beam, the dosimeters worn on the left side (the left Eye-Band and the left standard commercial casing dosimeter worn near the left eye) are shown to be inadequate in representing the dose at the left eye position, even at a slight angle of incidence of 30°. This is due to partial shielding of the left dosimeters by the operator's head as the head rotates to the left. Anthropomorphic eye lens dosimeters have proven to be an invaluable tool for gaining a comprehensive understanding of the various factors influencing dose estimation in ocular lens dosimetry from a metrological perspective. This approach effectively bridges the gap between the controlled type testing conditions of dosimeters and real-world workplace conditions, while maintaining standard radiation beam conditions.

Deep Neural Network to Classify Seabed Sediment Using MBES Multifrequency

This study investigates the classification of sediment distribution and types in inland waters using Artificial Neural Network (ANN) models based on multibeam echosounder data. Multibeam Echosounder Technology (MBES) is an acoustic instrument that emits high-speed sound pulses to map the bottom of water bodies. Valuable information about sediment characteristics can be obtained by analyzing the backscattering phenomenon, which measures the acoustic intensity reflected from the water bottom. The angular response curve (ARC) method, developed by Fonseca and Calder, is employed to analyze the relationship between backscatter intensity and the angle of reflection. The ANN models in this study are trained and tested using intensity values and angular response curves obtained from multibeam echo sounders. The ANN model architecture consists of an input layer, three hidden layers, and an output layer. The sigmoid activation function is utilized in the output layer, while the ReLU activation function is applied to the input and hidden layers. Performance evaluation demonstrates that the ANN model using uncorrected data achieves remarkable accuracy, with 100% accuracy obtained in both the training and testing stages. The model exhibits a training loss value of 0.059443 and a testing loss value of 0.110030, indicating its effectiveness in capturing patterns and reducing errors. Visualizing the sediment distribution in Waduk Selorejo reveals a relatively balanced presence of Clavey sand and Sandy silt sediment types. However, noticeable differences arise between the corrected and uncorrected data, which can be attributed to the alterations made during the data correction process. The best-performing ANN model achieves a testing accuracy of 0.75, indicating that it does not perfectly predict the given data. Acknowledging the potential for prediction errors when using corrected data is important.

Design of Broadband Circuit Analog Absorber With Optimal Thickness for Stable Angular Response in C, X, Ku, and K Bands

Design of Broadband Circuit Analog Absorber With Optimal Thickness for Stable Angular Response in C, X, Ku, and K Bands

Short time angular impulse response of Rayleigh beams

Short time angular impulse response of Rayleigh beams

High-performance narrowband thermal emitter based on aperiodic Tamm plasmon structures assisted by inverse design

Controlling the bandwidth and directionality of thermal emission is important for a broad range of applications, from imaging and sensing to energy harvesting. Here, we propose a new, to the best of our knowledge, type of long-wavelength infrared narrowband thermal emitter that is basically composed of aperiodic Tamm plasmon polariton structures. Compared to the thermal emitter based on periodic structures, more parameters need to be considered. An inverse design algorithm instead of traditional forward methodologies is employed to do the geometric parameter optimization. Both theoretical and experimental results show that the thermal emitter exhibits a narrowband thermal emission peak at the wavelength of 8.6 µm in the normal direction. The angular response of emission properties of the thermal emitter is dependent on the emission angle. We believe that our proposed thermal emitter provides an alternative for low-cost, high-effective narrowband mid-infrared light sources and would have a great potential in many applications.

A spherical neutron long counter for 4[formula omitted] neutron detection in the energy range of 0.01 eV to 20 MeV

Neutron detection using a long counter is the most commonly used method for accurate neutron flux measurement. It is desirable to design a long counter with a flat energy response and a consistent angular response. This requires counters to have neutron-energy-independent efficiency over a wide range of energies and a very slight dependence on the direction of neutron incidence in the 4π space. In this work, we designed a spherical neutron long counter using the Monte Carlo method, with a model consisting of a polyethylene ball, built-in air rings, and boron carbide material. The internal air rings enhance the energy response of thermal neutrons, spherical polyethylene improves the energy response of fast neutrons, and boron carbide material solves the problem of high local neutron energy response. We analyzed the energy response, angular response, and detection efficiency of long counters using neutron sources such as Pu–Be and Am–Be. The results show that the neutron energy response is relatively flat in the energy region of 0.01 eV to 20 MeV, the angular response is consistent in 2π space, and the maximum relative angular response deviation in 4π space is no more than 16.5%. We focus on the applicability of long counters in complex neutron fields, such as scattered neutron fields, and provide a reference for their use of long counters in neutron detection.

Groundtruther: A QGIS plug-in for seafloor characterization

This work focuses on developing a software system for concurrently analyzing co-located multibeam echo sounder (MBES) datasets and seafloor imagery, fulfilling the need for a unified seafloor data exploration and analysis platform. The system comprises a graphical user interface where image browsing and geospatial data are linked and several toolboxes for extracting backscatter distribution, its angular response, and bathymetric derivatives to ultimately build detailed quantitative reports. The overall objective is to provide an efficient means of understanding the relationships between morphology, backscatter, and the observed biota and, thus, understanding the relationship between the physical and ecological elements of the seafloor. In addition, Groundtruther provides new ways to interpret remotely sensed information derived from MBES and aid the development of spatial distribution models. Furthermore, it could lead to the enrichment of ground-truth databases used to develop formal geophysical models that link acoustic backscatter observations to intrinsic properties of the seafloor.

Angular dependence of the TL and OSL dosimeters in the clinical 6 MV photon Beam

The angular response of luminescent dosimeters (LD), in particular TLD and OSLD, has been compared by applying 6 MV X-ray photons from Versa HD clinical linear accelerator. The study admitted for the irradiation of TLD (n = 475) and OSLD (n = 475) under phantom set up in various gantry angles from 00 to ±900 and various field sizes from 10 x 10 cm2 to 30 x 30 cm2. The variance in the output was observed between 4.4% for TLD and 3.9% for OSLD. A significant deviation from the desired output was detected, towards the angle of incidents, at ±800 to ±900. Additionally, there is no evidence of variation in the dose measurement due to the difference in field size. These results demonstrate a good approximation to the vendor-specified tolerance limits, justifying the use of these LDs within angular incidents of radiation up to ±700. The TLD and OSLD better dose-response is achieved to a gantry angle up to ±700 from the perpendicular incidents. The result shows that both TLD and OSLD could be used as dosimeters for a treatment field that does not extend beyond ±700 beam angle.

Localising and identifying radionuclides via energy-resolved angular photon responses

A technique for the in-situ localisation of radioactivity is described whereby the energy-resolved angular photon response of a collimated inorganic scintillation detector is used to derive the spatial arrangement of a variety of radioactive source configurations. The influence of photon radiation (X- and γ ray) incident on the collimated detector is expressed mathematically, by way of a sinc transform embedded to a dynamic linear regression model, to increase the spatial accuracy of the localisation. This approach is tested experimentally with two pairs of like radionuclides, two pairs of different combinations of radionuclides and three different radionuclides to demonstrate its combined isotopic discrimination and spatial localisation capabilities. A fit based on the model referred to above is observed to reproduce the data for the combined X- and γ-ray regions of interest effectively. This allows for increased resolution via interpolation between the data which is observed to improve location accuracy significantly. This research is relevant to applications in autonomous robotic exploration tasks and for the characterisation of contaminated environments associated with nuclear legacies and radiological emergencies.

EURADOS intercomparisons on whole-body dosemeters for photons from 2008 to 2020: analysis and comparison of general results.

Starting in 2008 the European Dosimetry Group (EURADOS) has been performing international intercomparisons (ICs) on photon whole-body dosemeters for individual monitoring services. These ICs have been organized (on a biennial basis) starting 2008 up to 2020 now, each time with a similar set-up but with small alterations in the subsequent irradiation plans. The response for Hp(10) and Hp(0.07) was tested for different radiation qualities, angles of incidences (0°-60°) within a wide range of dose values (0.5-500mSv), to check energy and angular response, linearity, reproducibility and mixed-field response. Within the last 12years almost 15 000 whole body dosemeters have been irradiated and the corresponding response values evaluated. With an increasing number of participants and participating systems (from 62 to 132), this IC program has become an important tool for individual monitoring services to test their whole-body dosimetry systems, compare their results with other services or systems and to improve the quality of their dosimetry. The paper presents and compares the general results of these seven ICs and analyses the dosimetric results for the participating system types.

Development of ring radiation dosemeters using 3D printing.

Extremity radiation monitoring is an important tool for the assessment of occupational exposures to staff at a variety of workplaces where ionising radiation is used. This work shows the feasibility of applying 3D printing for the development of customisable ring dosemeters. The rings were developed using two types of resin, hard and flexible and has the possibility of sterilisation using different techniques. The printed ring dosemeter was associated with BeO optically stimulated dosemeters. The energy and angular response were found within ±20% in the energy range from 24 to 662keV and from 0° to 60° angle of incidence. This contributes to the reduction of measurement uncertainty when compared with currently used thermoluminescent detectors dosemeters. The new ring dosemeter showed a satisfactory response with respect to the performance criteria of the IEC 62387 Standard, in addition to providing improved ergonomics in relation to the commercial ring dosemeter.

EURADOS whole-body dosemeters intercomparisons: lessons learnt from individual results.

Every 2years since 2008, Eurados WG2 has organised a whole-body dosemeters intercomparison (IC) in photon and beta fields. This paper presents the information that individual participants can extract from their results. The irradiation plan of each IC was designed to allow participants check the performance of some important characteristics of their dosimetry systems, in particular: linearity, angular response, energy response and response to mixed fields. The analysis of anomalous responses indicates that many systems can reduce the number of outliers by improving their calibration procedures.