Specific Attenuation Research Articles

A Localized Quantitative Precipitation Estimation for S-band Polarimetric Radar in Taiwan

Abstract A polarimetric radar quantitative precipitation estimation to estimate rain rate (R) from specific attenuation (A) has been applied in Taiwan's operational Quantitative Precipitation Estimation and Segregation Using Multiple Sensors (QPESUMS) system since 2016. A 3-yrs' (2016-2018) drop size distribution dataset from an operational Parsivel network was used to derive a localized coefficient as well as the α(K) function in the R(A) scheme for S-band radar, where α is a key parameter in the estimation of A and K is the linear fitted slope of differential reflectivity (ZDR) versus reflectivity (Z). The local DSD data was also used to derive localized R(Z) and R(KDP) relationships, and the relationships were evaluated using radar observations in heavy rain cases. A synthetic QPE combining the localized R(A), R(Z), and R(KDP) relationships is compared to its operational counterpart and showed about 8 % reduction in normalized mean error for the Mei-Yu cases. Typhoon cases exhibited similar improvements by the localized QPE relationships, but showed higher uncertainties than in the Mei-Yu cases. The higher uncertainties in the typhoon QPE verification was likely due to the stronger winds in typhoons than in the Mei-Yu events that caused greater mismatches between the radar observations at an altitude and the gauges at the ground. Overall, the results demonstrated advantages of localized radar rainfall relationships derived from the disdrometer data to improve the accuracy of the operational rainfall estimation products.

Area-Based Rainfall Rate Model for Specific Attenuation in the Equatorial Region

Area-Based Rainfall Rate Model for Specific Attenuation in the Equatorial Region

A study on multi-channel active sound profiling algorithm for hybrid control of broadband and narrowband noise inside vehicles

The vehicle interior noise consists of both broadband road noise and narrowband engine order noise. Currently, the road noise control (RNC) system and engine noise control (EOC) system operate independently in engineering applications. This paper introduces a novel multi-channel hybrid broadband and narrowband active noise control (HBNANC) algorithm, designed to simultaneously attenuate road noise and engine order noise inside vehicles. On this basis, by integrating an error signal design (ESD) subsystem and a sinusoidal error separation (SES) subsystem, a multi-channel hybrid broadband and narrowband active sound profiling (HBNASP) algorithm is further proposed, enabling specific attenuation or amplification of individual narrowband components to meet subjective acoustic comfort requirements. The paper validates the algorithms’ effectiveness and robustness through simulations, and real vehicle experimental measurements under various conditions. The research offers a comprehensive approach to enhancing the auditory experience inside vehicles, contributing to the advancement of active noise control technology.

Controllable multi-soliton spectral tunneling by airy pulses in photonic crystal fiber

A straightforward method to induce tunable multi-soliton spectral tunneling (SST) using a finite energy Airy pulse in a photonic crystal fiber (PCF) featuring three zero-dispersion wavelengths is proposed numerically in the paper. The study reveals that the distinctive multi-envelope structure of the Airy pulse enables the control of tunneling distances, properties, and soliton numbers through modulation of its attenuation factor and peak intensity. Notably, the SST process involving the Airy pulse generates multiple blue-shifted and red-shifted dispersion waves, along with associated trapping waves, contributing to the formation of an ultra-flat and ultra-wide supercontinuum. Furthermore, the velocity and efficiency of multi-SST can be manipulated to enhance the overall tunability of the phenomenon. The findings underscore the potential application of Airy pulse-driven SST in secure multi-frequency signal transmission and controlled supercontinuum generation, with the tunability of these processes being governed by the specific attenuation factor and peak power settings of the input Airy pulse. This work advances the understanding of multi-SST dynamics in PCFs and provides a theoretical framework for exploiting these dynamics in practical information security and optical spectrum management contexts.

Dependence of rain attenuation on rain rate and drop size distribution for Ka-band satellite communication over India

The Raindrop size distribution (DSD) is the most effective parameter to calculate rain-induced attenuation, which can be severe at Ka-band and higher frequencies. The authors have investigated the impact of rain rate and DSD on rain-induced specific attenuation over a tropical location Kolkata, India. DSD data from disdrometer has been used to calculate the specific rain attenuation with the help of Mie scattering theorem. Low to medium drop diameters (up to 3 mm) are the largest contributors to the various classes of rain rate and attenuation. Double peaks of drop sizes are significant for medium rain rate. The contribution of smaller drop diameters decrease, whereas the contribution of higher drop diameters increase with increasing rain attenuation. At lower rain attenuation, (up to 1.5 dB), complementary cumulative distribution function (CCDF) shows higher value for stratiform rain, with respect to convective rain. The higher attenuation occurrences are mostly observed during 12–18 Indian standard time (IST), i.e., in the afternoon. The results will be helpful for Ka-band (GSAT-14) and higher frequency satellite communication channel modeling over India.

A novel method for holdup measurement of three phases by an ultrasonic device with the flexible substrate

The precise measurement of multiphase flow holds significant importance across diverse industrial contexts. However, rigid probes struggle with the variable dimensions of curved surfaces, while flexible probes are hindered by fragility, susceptibility, and challenges in large-scale production. Herein, we propose an ultrasonic device featuring a flexible substrate that seamlessly amalgamates flexibility and rigidity to enable precise measurement of three-phase flow. Through simulation, we determine the optimal ultrasonic frequency (1 MHz) and flexible substrate thickness (3 mm) for a specified probe and pipe size (20 mm). A novel concept, the specific attenuation coefficient (SAC), derived from the voltage-amplitude of transmitted and received signals and propagation distance, is introduced to differentiate between oil and water. The discrepancy between measured and actual three-phase holdups are 0.55 %, 0.36 %, and 0.59 % for water, gas and oil, respectively, with a variance of measurement results 0.027.

Dual-Energy CT in Oncologic Imaging.

Dual-energy CT (DECT) is an innovative technology that is increasingly widespread in clinical practice. DECT allows for tissue characterization beyond that of conventional CT as imaging is performed using different energy spectra that can help differentiate tissues based on their specific attenuation properties at different X-ray energies. The most employed post-processing applications of DECT include virtual monoenergetic images (VMIs), iodine density maps, virtual non-contrast images (VNC), and virtual non-calcium (VNCa) for bone marrow edema (BME) detection. The diverse array of images obtained through DECT acquisitions offers numerous benefits, including enhanced lesion detection and characterization, precise determination of material composition, decreased iodine dose, and reduced artifacts. These versatile applications play an increasingly significant role in tumor assessment and oncologic imaging, encompassing the diagnosis of primary tumors, local and metastatic staging, post-therapy evaluation, and complication management. This article provides a comprehensive review of the principal applications and post-processing techniques of DECT, with a specific focus on its utility in managing oncologic patients.

A 30-year (1992-2021) time-series of Kd(PAR) at the North Sea - Baltic Sea transitional zone - trends in light attenuation and Chlorophyll a

Light attenuation is of fundamental importance for photosynthesis in marine and freshwater environments and quantified as Kd(PAR). A 30-year (1992–2021) long time-series of Kd(PAR) (n = 945) from Aarhus Bay, at the North Sea - Baltic Sea transition obtained with 1–5 measurements per month is analyzed. The time-series showed a weak but not statistically significant positive trend with an average Kd(PAR) of 0.30 ± 0.08 m−1. Monthly based time-series of Kd(PAR) showed, in comparison, significant differences with average maximum values in March of 0.38 ± 0.09 m−1 compared to a minimum in June of 0.26 ± 0.03 m−1. There were statistically significant positive Kd(PAR) trends in April and December and a negative trend in October. Accordingly, the depth limit of eelgrass and macroalgae decreased from 8 to 5 m in April. The strong variability in Kd(PAR) in February and March related to the phytoplankton spring bloom in Aarhus Bay both in timing and strength, given the strong and significant correlation between Chl a and Kd(PAR). Partitioning showed that non-Chl a attenuation related to CDOM and suspended matter increased from 0.20 m−1 to 0.29 m−1 between 1992 and 2007 but was constant from then on. The Chl a specific attenuation coefficient varied around an average of 0.019 ± 0.008 m2 (mg Chl a)−1 and showed only small variations over time. The frequency of CTD casts and light measurements decreased between 1992 (n = 52 per year) and 2022 (n = 15 per year) but no parallel trends in average Kd(PAR) were observed. No significant trend (1992–2021) in annual average Chl a concentrations in Aarhus Bay was detected. The importance of high-resolution measurements in time are emphasized and at least monthly to track the strong seasonal variation.

Study on effect of charged sand/dust atmosphere on the performance of microwave quantum illumination radar

This paper aims to study the effects of charged sand/dust atmosphere on the performances of microwave quantum illumination (QI) radar. Based on Mie particle scattering theory, using a Monte Carlo method for simulating the physical process which photon is scattered multiple times by discrete random distributed particles, the specific attenuation (dB/km) of microwave propagating in sand/dust atmosphere are analyzed under the conditions of varying atmospheric visibility and sand/dust particles with different charged quantities. It is indicated that the specific attenuation obtained by multiple scattering is smaller than those obtained based on Mie theory, for microwave propagating in charged sand/dust atmosphere. The smaller the atmospheric visibility, the greater the difference, while the difference decreases gradually as the atmospheric visibility increases. Then, it is more reasonable to consider multiple scattering attenuation at lower atmospheric visibility. When sand/dust particle is charged, the specific attenuation is increased, however, this increase is not linear. According to quantum illumination radar theory, a beam splitter-based optical link model is used to simulate the sand/dust atmospheric channel. The effects of charged sand/dust atmosphere with different visibility on the detection error probability, signal-to-noise ratio, and maximum detection range for microwave quantum illumination radar are studied by using quantum radar equation and quantum detection error probability theory. The performances of QI and classical two mode noise (TMN) radar are compared and analyzed. These results show that the performances of quantum illumination radar are improved with increasing sand/dust atmospheric visibility. When sand/dust particle is charged, the performances for QI radar are degraded due to attenuation increase. The change in the performances is nonlinear as the change in sand/dust carrying charge quantity. Increasing the signal frequency can enhance the performance of quantum illumination radar when visibility is high, but when visibility is low, the gain from frequency increase is outweighed by the performance degradation caused by increased attenuation, making it inadvisable to raise the frequency in such cases. The comparison with classical radar reveals that QI radar performs better under the condition of lower atmospheric visibility and lower average photon emission, but this advantage diminishes as the number of photons increases. In a word, these results show that the performances of QI radar are more significant at lower atmospheric visibility. Under higher visibility conditions, the QI system SNR can be improved by increasing frequency. The maximum detection range of the QI radar is significantly better than the classical TMN radar.

A Cascaded Multimodule Image Enhancement Framework for Underwater Visual Perception.

Underwater images usually exhibit severe color cast, hazy appearance, and/or dark regions because of the complex lighting absorption and scattering in water. How to increase the quality of these degraded underwater images has emerged as a key issue for various underwater application tasks. Recent efforts have been made to deal with single type degradation, however, it is still challenging to deal with multiple degradations that usually coexist in an underwater image with a general network. The degradations in underwater images can be divided into medium-agnostic (hazy or low-light which also encountered in in-air images) and medium-specific (color distortion caused by the specific light attenuation property in water) ones. According to this observation, this article proposes a cascaded multimodule underwater image enhancement (UIE) framework to address the coexisted multiple degradations. In the proposed framework, an in-air image enhancement module and a novel proposed adaptive color channel compensation network (AC 3 Net) are cascaded, in which the former focuses primarily on solving medium-agnostic degradations and the latter is for handling the medium-specific degradation. This framework has good flexibility by cascading different types of in-air image enhancement networks with AC 3 Net to achieve various UIE. The effectiveness of the proposed framework has been extensively validated on various degraded underwater images as well as different underwater visual perception tasks.

Mussel and Cobweb Inspired High Areal Capacity SPAN Electrode.

Lithium-sulfur batteries (LSBs) with superior energy density are among the most promising candidates for next-generation energy storage techniques. Sulfurized polyacrylonitrile (SPAN) exhibits competitive advantages in terms of cycle stability, rate performance as well as cost. However, the preparation of high-loading SPAN electrodes is still challenging. Herein, inspired by mussel and cobweb, a high-loading SPAN electrode is enabled by the combination of polydopamine (PDA) coating and a bimodal distributed single-wall carbon nanotubes (SWCNT) slurry dispersed in polyvinylpyrrolidone (PVP), their synergistic effect not only constructs effective electron percolating networks within the electrode but also make high active material (AM) ratio possible. High areal capacity PDA@SPAN electrode (18.40mAhcm-2 in the initial cycle) with negligible specific capacity attenuation as the mass loading increasement is realized through the facile slurry casting process. The dynamic N─H…O hydrogen bond is formed between PDA and PVP and the electrode integrity during charge/discharge is greatly strengthened. The battery with an areal AM loading of 7.16mgcm-2 (5.16mAhcm-2) retains 92.0% of capacity in 80 cycles and 87.18% in 160 cycles, and it also shows stable cycle performances even with a high loading of 19.79mgcm-2 and lean electrolyte (3.28µLmg-1).

Rain Attenuations Based on Drop Size Distribution (DSD) Model and Empirical Model at Low THz Frequencies

Rain attenuation based on the drop size distribution (DSD) with different rainfall rates (R) at low THz frequencies is investigated in this paper. The rain attenuation is calculated using the DSD measured for one year and the extinction cross-section (ECS) by the Mie scattering theory. Moreover, the obtained specific rain attenuation is verified by the empirical model using the measurement system consisting of a transmitter, a receiver, and weather measurement units. We measured the received power against the uniform transmitted power at 240, 270, and 300 GHz on the rooftop of the National Radio Research Agency (RRA) in Korea during the same period as the DSD measurement period. After curve fitting by regression analysis, we compared both rain attenuations obtained in two methods with the recommendation International Telecommunication Union Radiocommunication Sector (ITU-R) P.838-3. The root mean square errors (RMSEs) of the DSD model are 2.8977, 2.8646, and 2.8331 at 240, 270, and 300 GHz, respectively. The calculated result using the Mie scattering and the measured DSD methods shows the best fit to the data of the ITU-R recommendation for a rainfall rate of up to 5 mm/h. On the other hand, the empirical results using the T/Rx antenna system are slightly higher compared to the data of the ITU-R recommendation. As the rainfall rate increases, the difference between our results and ITU-R recommendation increases. This study will be useful for predicting rain attenuation for terrestrial wireless links operating at low THz frequencies.

Comparison of four radar profiling algorithms in the S‐band

AbstractRadar profiling algorithms are widely used for precipitation‐induced path‐attenuation correction. In this study, we investigate the impact of the four well‐known profiling algorithms on the efficacy of quantitative precipitation estimation retrievals. The first method, named the “simple PhiDP‐based method”, distributes precipitation‐induced path attenuation, or PhiDP (differential phase shift), of a rain segment to each radar gate according to radar reflectivity (Zh). The second one is a linear version of the ZPHI method derived from an approximate linear relationship between specific attenuation (Ah) and specific differential phase (KDP). The third one is a nonlinear version of the ZPHI that respects the nonlinearity of the Ah–KDP relationship. The fourth method is inspired from the self‐consistent method of Bringi. The two‐moment normalized raindrop size distribution (DSD) with two variables, scaled drop concentration and mean drop diameter , is used to represent natural variability of DSD. Two configurations are considered: a constant over a segment and a variable over a segment. The Ah, KDP, and rain intensity are estimated by the four profiling algorithms. The sensitivity of each algorithm to radar measurements uncertainty is also investigated. The evaluation of the estimates shows the following. First, for the range‐constant situation, the nonlinear ZPHI and the self‐consistent method yield the best estimates if the measurements errors are not considered. However, the nonlinear ZPHI and the self‐consistent method are significantly impacted by the Zh bias and the measurements noises respectively. Second, for the range‐variable situation, the self‐consistent method does not have a good performance even when radar measurements are accurate. The performance of the nonlinear ZPHI method is similar to the simple PhiDP‐based method, whereas the latter is immune to the Zh calibration error. These results suggest that the benefit of introducing in quantitative precipitation estimation algorithms can be significantly reduced if is not constant in reality and/or if the radar measurements are biased and noisy.

Preliminary study of reuse of plastic bottles as metamaterial

The present work introduces a novel approach to designing metamaterial for low frequency and high frequency wave attenuation by repurposing plastic waste. The metamaterial is constructed using a duct-like structure with a periodic arrangement of bottles of different sizes. This configuration leads to the formation of a local resonant band, which spans from 240 to 340 Hz. In both the numerical model and the experimental setup, a harmonic excitation is given to the proposed configuration and transmission loss is computed as a function of frequency. The experimental results support the findings obtained from numerical simulations, confirming the effectiveness of the designed metamaterial. One crucial aspect discovered in this work is that introducing space between the bottle’s neck and the side wall of the structure causes the bottles to act as Helmholtz resonators. Thus, in turn, this results in an additional band gap at low frequencies, complementing the existing Bragg’s band gap achieved by the periodic arrangement of bottles. The ability to change the size of the bottles gives control over the position of the band gap, allowing for greater flexibility in tailoring the metamaterial to specific noise attenuation requirements. The applications of these plastic bottle-based metamaterials are wide ranging, especially in improving the indoor acoustic environment of buildings. This work opens up a new avenue for further exploration and innovation in the field of sustainable and environmentally friendly metamaterials.

Computed tomography defined femoral artery plaque composition predicts vascular complications during transcatheter aortic valve implantation.

Vascular and bleeding complications after transcatheter aortic valve implantation (TAVI) are common and lead to increased morbidity and mortality. Analysis of plaque at the arterial access site may improve prediction of complications. We investigated the association between demographic and procedural risk factors for Valve Academic Research Consortium (VARC-3) vascular complications in patients undergoing transfemoral TAVI with use of a vascular closure device (ProGlide® or MANTA®) in this retrospective cohort study. The ability of pre-procedure femoral CT angiography to predict complications was investigated including a novel method of quantifying plaque composition of the common femoral artery using plaque maps created with patient specific X-ray attenuation cut-offs. 23 vascular complications occurred in the 299 patients in the study group (7.7%). There were no demographic risk factors associated with vascular complications and no statistical difference between use of closure device (ProGlide® vs MANTA®) and vascular complications. Vascular complications after TAVI were associated with sheath size (OR 1.36, 95% CI 1.08-1.76, P 0.01) and strongly associated with CT-derived necrotic core volume in the common femoral artery of the procedural side (OR 17.49, 95% CI 1.21-226.60, P 0.03). Plaque map analysis of the common femoral artery by CT angiography reveals patients with greater necrotic core are at increased risk of VARC-3 vascular complications. The novel measurement of necrotic core volume in the common femoral artery on the procedural side by CT analysis was associated with post-TAVI vascular complications, which can be used to highlight increased risk.

Ventilated silencer based on layered Helmholtz resonators

This study investigates the performance of a multilayer sound-attenuating metamaterial with ventilation capabilities. The design incorporates arrays of Helmholtz resonators embedded within the wall structure. Each cell of the barrier's front wall is a Euclidean polygon, triangular, square, or hexagonal, housing a parallel array of resonators interconnected via an axial ventilation duct. The sound attenuation performance of these barriers is meticulously examined using the lumped parameter theory and the transfer matrix method (TMM), complemented by finite element (FE) simulations. The results indicate that sound attenuation in the audible frequency range (300–2000 Hz) can be significantly enhanced by employing multiple layers of resonators, each layer assigned a unique peak resonance frequency. Despite the design's inherent trade-offs between barrier thickness, ventilation capacity, operational frequency range, and overall sound attenuation, its structural simplicity and straightforward theoretical performance estimation methods make it a promising candidate for applications requiring a specific attenuation spectrum. The sound-blocking performance of the design is further validated through impedance tube experiments, which show a reasonable agreement with the numerical predictions, thereby affirming the efficacy of the proposed design. The performance of multilayer design is also compared with the similar ventilated barriers proposed in the recent studies.

Relevance of photocatalytic redox transformations of selected pharmaceuticals in a copper- and iron-rich Mediterranean intermittent river

This work aimed at investigating specific attenuation pathways of pharmaceuticals in copper- and iron-rich Mediterranean intermittent and sunlit rivers by combining lab- and field-scale studies. Poorly photodegradable and biodegradable compounds such as fluconazole, oxazepam and venlafaxine attenuated in two river stretches with short hydraulic residence times (<3 h). This result was assumed to be related to their capacity to interact with photoreactive free Cu2+ and Fe3+ or their associated oxides. Lab-scale photodegradation experiments under simulated solar irradiation revealed the beneficial impact of a mixture Cu2+ and colloidal iron hydroxides at environmental concentrations and at neutral pH on the pharmaceuticals photodegradation kinetic rate constants. These latter were consistent with the in-stream attenuation rate constants of targeted contaminants which ranged from 0.104 to 0.154 h−1. Further identification of phototransformation products by LC-HRMS highlighted reductive transformation pathways including reductive dehalogenation and hydrogenation reactions. Several TPs were found to be stable under irradiation and were detected in field monitoring, accordingly. This was ascribed to the formation of a Cu/Fe composite material under solar irradiation with photocatalytic properties. The role of Cu was to trap the electron in the conduction band of the iron-based photocatalyst, which promoted separation efficiency of electron-hole pairs as well as enhanced photoreduction processes at the expense of oxidation ones. Even though, these mechanisms have been reported in water treatment field for organic micropollutants removal, their significance was demonstrated for the first time in natural settings.

The propagation loss of ultrashort laser pulses in water clouds

When a high-power laser beam is incident on water clouds, often along with optical breakdown occurs. In that case, the droplet becomes highly opaque and strongly absorbs incident laser light. In this study, we construct a transient coupling model to elucidate the evolution of the light field and the distribution of plasma in the interaction between laser and cloud droplet in detail, and further quantify the nonlinear absorption of droplet under the action of high-power laser. The results showed that linear dependence existed between the proportion of absorbed energy by the droplet and the incident laser wavelength at the same laser energy. Such a relationship, combined with existing scattering theory, can be used to evaluate the propagation distance of the ultrashort laser in water clouds and the specific light attenuation under different parameters. In the same type of water cloud, the laser propagation distance decreases with increasing laser intensity, thereby confirming the availability of non-linear absorption on the laser propagation. Furthermore, a smaller pulse duration typically corresponds to a larger peak power, which results in stronger non-linear absorption and a shorter propagation distance in water clouds. On the other hand, a comparison of laser propagation distances in different types of water clouds reveals that scattering effects dominate in dense water clouds, with stronger propagation losses to the incident laser. Finally, the light attenuation in different water clouds is given accordingly. This study opens up new perspectives for the assessment of laser propagation loss in different water clouds and the propagation distance.

UAV Communication Recovery under Meteorological Conditions

Our study proposes a UAV communications recovery strategy under meteorological conditions based on a ray tracing simulation of excessive path loss in four distinct three-dimensional (3D) urban environments. We start by reviewing the air-to-ground propagation loss model under meteorological conditions, as well as the specific attenuation of rain, fog, and snow, and we propose a new expression for line-of-sight (LoS) probability. Using the two frequency bands of 28 GHz and 71 GHz, we investigate the impact of specific attenuation caused by different weather conditions and analyze the relationship between the radius of the UAV coverage area and the elevation angle. Furthermore, we investigate the effects of the rainfall rate, liquid water density, and snowfall rate on the maximum coverage area and optimal height of the UAV. Eventually, we propose a strategy that involves compensating for the maximum path loss and adjusting the UAV’s position to recover the coverage of the UAV to ground users. Our results show that rain has the greatest impact on the UAV’s coverage area and optimum height among the three types of weather conditions. For various weather conditions, relative to Region 1, the percentage reduction in the maximum coverage radius of Region 2 to Region 4 increases gradually, and the extent of each increase is approximately 10%. Moreover, after adding the compensated path loss, the coverage radius of the UAV in the four regions is restored to a value slightly larger than that before the rain. In addition, rain caused the greatest reduction in UAV coverage for suburban environments and the lowest for high-rise urban environments.

Elevation angle effect on slant path attenuation along earth-space paths: A Northern Nigeria perspective

In the network planning and design of terrestrial and earth-space communication links, the slant path attenuation caused by rain and its associated strong winds is of interest. Rain causes severe link degradation to radio links by absorbing parts or the whole signal during propagation. This study predicts slant path attenuation by rain in three (3) Northern Nigerian zones using the International Telecommunications Unions (ITU-R) model for 10 to 40 GHz. The effect of specific attenuation, rain attenuation, and elevation angle on the received signal strength is analyzed. The ITU-R model suggests rain attenuation values ranging from 4.26 dB to 31.67 dB for Jaji, Wudil, and Potiskum. The results further indicate a decrease in rain attenuation with an increase in elevation angle up to 50.1° elevation for the three (3) monitored stations, which starts to decrease steadily after this threshold. Results from this study can aid the network engineer in anticipating network changes and planning fade mitigation techniques where necessary.