Total Attenuation Research Articles

Fiber To The Home Access Network Planning With Gpon Technology Using Genetic Algorithm Method

The purpose of this research is to plan the Fiber To The Home access network at a location in the city of Soe, Kupang, East Nusa Tenggara. This planning is done to facilitate the construction of the Fiber To The Home network from the center to the customer. Researchers conducted a design based on ODP sample point data based on MAPS from the company PT Arsenet Global Solution Soe Branch, the results of simulations conducted in Matlab and OptiSystem software. In this study, the best route search was carried out for the construction of the Fiber To The Home network using the Genetic Algorithm method, the results of the best route search obtained the shortest route as far as 1.6646 km from the center to the customer. Also obtained 7 ODP points with ODP routes starting from ODP points 2-3-4-5-6-7-1 with the distance of each point to the point 0.0045 km - 0.1466 km - 0.1361 km - 0.1042 km - 0.4396 km - 0.8305 km - 0.0031 km. The results of the simulation of the genetic algorithm design in matlab will be simulated in the optisystem 7.0 software to get the receiving power and Bit Eror value. The simulation results using optysystem will be a reference for calculations using the Power Link Budget method. The Power Link Budget calculation shows the total attenuation value from the center to the customer of 18.7925 dB with a power margin of 3.2 dB, Bit Eror of 5.64838 x 10-24 and Q Factor of 10.0288. The results of the calculation of attenuation and power margin prove that the planning is said to be feasible because the total planning attenuation results are below the attenuation standard set by the company PT Arsenet Global Solusi which is a maximum of 28 dB, as well as having a power margin value of more than 0 and a BER value that meets the standard.

Numerical evaluation of vertical and horizontal distances for nitrogen attenuation from Onsite Sewage treatment and disposal systems (OSTDS)

Onsite Sewage Treatment and Disposal Systems (OSTDS) used for domestic wastewater treatment are a source of nitrogen (ammonium and nitrate) contamination to groundwater and surface water. One way to manage the contamination is to establish setback distances for nitrogen attenuation through nitrification and denitrification reactions within the setback distances. Determining the setback distances requires investigating nitrogen attenuation as a function of distance from OSTDS. While field investigations have been conducted, there have been few modeling investigations. Using an ArcGIS-based Nitrogen Load Estimation Toolkit, this study simulates nitrogen attenuation for over 20,000 OSTDS at five study areas across Florida, where a third of households are served by OSTDS. Different from conventional studies that only consider the horizontal distances (between an OSTDS and a surface water body that receives OSTDS effluents), this study also considers the vertical distances (between an OSTDS drainfield and water table beneath the drainfield) to account for the nitrogen reactive transport processes in the vadose zones and groundwater aquifers, making the assessment of nitrogen attenuation more comprehensive. Modeling results yield the following three empirical but quantitative relations: (1) vertical attenuation rate as a function of vertical distance and saturated hydraulic conductivity (Ks) available in the Soil Survey Geographic Database, (2) horizontal attenuation rate as a function of horizontal distance and Ks, (3) total attenuation rate as a multiplication of the vertical and horizontal attenuation rates. These relations can be used to determine nitrogen attenuation within vertical and horizontal distances to OSTDS for practical management of OSTDS nitrogen contamination.

Seismic moment of local earthquakes in the central part of the Baikal rift by the coda envelope inversion

The article presents an estimation of scalar seismic moment by the coda envelope inversion of local earthquakes recordings in the central part of the Baikal rift zone. In addition to the earthquake source parameters, the method allows us to simultaneously estimate seismic energy loss and site amplification factors for frequency bands from 0.53 to 34 Hz. Because of the compromise between spectral source energy and site responses, we estimated amplification factors for used stations relative to the "UlanUde" (UUDB) reference site located in crystalline rock. In order to estimate intrinsic and scattering attenuation we used events recorded at three broadband seismic stations and epicentral distances between 40 and 120 km. The result suggests that intrinsic absorption is dominant over scattering attenuation in the central part of the Baikal rift zone for most frequency bands, but the seismic albedo B0, expressing the contribution of scattering to the total attenuation, showed variations from 0.23 to 0.6 for frequencies below 1 Hz, with mean B0 value 0.33. Attenuation and siteamplification factors were used to estimate the seismic moment and moment magnitudes Mw of local earthquakes. The resultant moment magnitudes exhibit a good agreement with routinely reported local magnitude (ML) estimates for the study area. The coda inversion estimates of seismic moment provide stable, unbiased moment magnitudes for events that are too small to be seen at teleseismic distances.

The Low-Attenuation Endfire Leaky-Wave State on an Optically Transparent Lossy Film

The development of high-performance optically transparent radio frequency (RF) radiators is limited by the intrinsic loss issue of transparent conductive films (TCFs). Instead of pursuing expensive endeavors to improve the TCFs’ electrical properties, this study introduces an innovative approach that leverages leaky-wave mode manipulation to mitigate the TCFs’ attenuating effect and maximize the RF radiation. Our finding reveals that the precise control of the mode confinement on glass-coated TCFs can create a low-attenuation window for leaky-wave propagation, where the total attenuation caused by TCF dissipation and wave leakage is effectively reduced. The observed low-attenuation leaky-wave state on lossy TCFs originates from the delicate balance between wave leakage and TCF dissipation, attained at a particular glass cladding thickness. By leveraging the substantially extended radiation aperture achieved under suppressed wave attenuation, this study develops an optically transparent antenna with an enhanced endfire realized gain exceeding 15 dBi and a radiation efficiency of 66%, which is validated to offer competitive transmission performance for advancing ubiquitous wireless communication and sensing applications.

Physical properties of strong 1 < z < 3 Balmer and Paschen line emitters observed with JWST

Context. The ultraviolet continuum traces young stars while the near-infrared unveils older stellar populations and dust-obscured regions. Balmer emission lines provide insights into gas properties and young stellar objects but are highly affected by dust attenuation. The near-infrared Paschen lines suffer less dust attenuation and can be used to measure star formation rates (SFRs) in star-forming regions obscured by dust clouds. Aims. We present a new way of combining spectro-photometric data in order to test the robustness of the SFRs and stellar mass estimates of star-forming sources observed with JWST. We also aim to quantify the amount of differential attenuation between the interstellar medium and the birth clouds with the use of Paschen emission lines. Methods. We select 13 sources between redshifts 1 and 3 observed with HST, JWST/NIRCam and NIRSpec based on the availability of at least one Balmer and one Paschen line with S/N ≥ 5. With a newly developed version of CIGALE, we fit their hydrogen line equivalent widths (EWs) and photometric data. We assess the impacts of the removal of spectroscopic data by comparing the quality of the fits of the spectro-photometric data to those with photometric data only. We compare the single (BC03) vs binary (BPASS) stellar population models in the fitting process of spectro-photometric data. We derive the differential attenuation and explore different attenuation recipes by fitting spectro-photometric data with BC03. For each stellar model and for each input dataset (with and without EWs), we quantify the deviation on the SFRs and stellar masses from the “standard” choice. Results. The combination of spectro-photometric data provides robust constraints on the physical properties of galaxies, with a significant reduction in the uncertainties compared to using only photometric data. On average, the SFRs are overestimated and the stellar masses are underestimated when EWs are not included as input data. We find a major contribution of the Hα emission line to the broadband photometric measurements of our sources, and a trend of increasing contribution with specific SFR. Using the BPASS models has a significant impact on the derived SFRs and stellar masses, with SFRs being higher by an average of 0.13 dex and stellar masses being lower by an average of 0.18 dex compared to BC03. We show that a flexible attenuation recipe provides more accurate estimates of the dust attenuation parameters, especially the differential attenuation. Finally, we reconstruct the total effective attenuation curves of the most dust-obscured galaxies in our sample.

Advanced ternary carbon-based hybrid nanocomposites for electromagnetic functional behavior in additive manufacturing

This study explores the processing and performance of acrylonitrile butadiene styrene (ABS)-based carbon ternary hybrid nanocomposites, incorporating carbon nanotubes (CNT), graphene nanoplatelets (GNP), and carbon black (CB), for applications in electromagnetic compatibility (EMC). The effect of nanocomposite processing on electromagnetic properties was evaluated by varying the mixing protocol, either through direct extrusion with simultaneous addition of all constituents or by preparing a master batch followed by dilution. The impact of nanofiller morphology and processing techniques on the behavior of nanocomposites was systematically investigated. Filaments of these nanocomposites were Additive Manufactured via Material Extrusion, and the resulting parts were evaluated for EMI shielding effectiveness (SE) in the X-band frequency range. The study reveals that the morphology, influenced by the processing strategy, significantly impacts the EMI SE properties of the printed samples. Particularly, ternary hybrids 3/3/3 wt% (CNT/GNP/CB) nanocomposites demonstrate promising electrical (0.003 S/cm), electromagnetic (29 dB of total attenuation), and mechanical performance (elastic modulus of 3080 MPa), with a clear advantage observed in those processed via direct extrusion. These nanocomposites were validated as feedstock filaments for 3D printing, and the printed sample exceeds the injection molded behavior for the composition 3/3/3 wt% (CNT/GNP/CB), achieving 40 dB of total attenuation at 11.8 GHz. The findings contribute valuable knowledge into tailoring nanocomposite formulations for additive manufacturing applications in EMI shielding, providing a nuanced understanding of the interplay between processing strategies, nanocomposite morphology, and resulting material properties.

Laboratory Study on Wave Attenuation by Elastic Mangrove Model with Canopy

This study evaluates the effectiveness of artificial Kandelia obovata forests in wave attenuation through physical model experiments conducted in a wave flume. The experiments meticulously replicated real-world hydrodynamic conditions and mangrove movement responses using the principles of gravitational and motion similarity, with a scaled 1:10 model of Kandelia obovata. Our approach included comparative experiments against a 1:100 gradient concrete slope to isolate the effects of seabed friction and flume wall reflections. The wave height was measured using strategically placed wave gauges. The findings indicated that the artificial Kandelia obovata forests significantly attenuated waves, with a decrease in the total attenuation capacity as the water depth increased from 2.75 m to 3.28 m under both regular and irregular waves. The elastic mangrove model with a canopy effect led to a 15% increase in wave attenuation over cylindrical models. Predictive models using multivariate nonlinear regression and back propagation neural networks showed that the latter provided a superior accuracy in estimating wave transmission coefficients

The possibility of using the DKS-AT1123 dosimeter for radiation monitoring of medical electron accelerators with the energy of more than 10 MeV

In the Russian Federation, there is a constant increase in the number of radiation medical installations with electron accelerators. Over the past 4 years, their number has increased 2.5 times. These installations contain pulsed electron accelerators that generate pulsed bremsstrahlung radiation with a maximum energy from 6 to 21 MeV. Currently, there are no devices designed for dosimetry of the pulsed photon radiation with energy of more than 10 MeV in the state register of measuring instruments of the Russian Federation. The most widely used radiation monitoring device for pulsed electron accelerators is the DKS-AT1123 X-ray and gamma radiation dosimeter designed for dosimetry of pulsed bremsstrahlung radiation with an energy of up to 10 MeV. The purpose of this work is to evaluate the possibility of using this device for dosimetry of pulsed bremsstrahlung radiation with a maximum energy of up to 20 MeV. The authors calculated the energy spectra of bremsstrahlung radiation for a point source with a maximum energy of 20 MeV behind flat concrete screens with a thickness of 1 m, 2 m and 3 m by the Monte Carlo method using the GEANT4 calculation program. The energy dependence of the registration efficiency of the DKS-AT1123 dosimeter was extrapolated to the energy range of 10–50 MeV in the kerma-approximation without taking into account the energy transfer by secondary electrons. It was assumed that it corresponds to the energy dependence of the total mass attenuation coefficient for the absorbed energy of gamma quanta in water. Using conversion coefficients for converting the fluence of monoenergetic photons into the effective dose rate at an anterior-posterior radiation incidence on the human body, real dose rates were calculated, and using the energy dependence of the dosimeter readings, the predicted results of measuring the unit dose rate with the DKS-AT1123 dosimeter behind a concrete protection with a thickness of 1, 2 and 3 m were obtained. It is shown that the maximum expected underestimation of the measurement results will not exceed 40% and practically does not depend on the thickness of the concrete shield in the thickness range from 1 to 3 m. To account for this underestimation, it is necessary to use the value of additional measurement error due to the energy dependence of the sensitivity of this device for the photon radiation energy of more than 10 MeV, equal to 70%. This makes it possible to use the measurement results obtained using this dosimeter to adequately characterize the state of radiation safety during operation of pulsed electron accelerators with a maximum energy of up to 20 MeV. It is possible to use a correction factor to the measurement results equal to 1.63 ±0.04 to compensate for this underestimation. The proposed approach can be used to create a methodology for using this dosimeter for radiation monitoring of medical electron accelerators with the energy of up to 20 MeV, if there are correction factors for radiation protection configurations and radiation energies encountered in practice.

Impedance-matched coplanar-waveguide metal-powder low-pass filters for cryogenic applications.

We developed impedance-matched metal-powder low-pass filters based on coplanar waveguide design and characterized them at room temperature and 77.4K. The coplanar waveguide metal-powder (CPW-MP) filters have a return loss better than 9.8 dB at frequencies up to 10GHz at 77.4K. We find that the filter attenuation per length scales linearly with frequency from 29 to 220 dB/m within the 1-5GHz frequency range at 77.4K, achieving the total attenuation above 100 dB for the 1 m-long CPW-MP filter at frequencies above 2GHz. The CPW-MP filter integrated with the multipole LC filter demonstrates the low cut-off frequency, the attenuation above 100 dB in the stop band, and the high roll-off of 590 dB per decade. The proposed CPW-MP filter is easy to fabricate, has very good thermal-shock resistance, is flexible for integration with other types of low-pass filters, delivers the same performance as classical cryogenic filters, is more compact compared to 50Ω coax cables with the same type of lossy dielectric, and provides ample opportunities for further miniaturization.

The hazardous protective glass material for gamma, neutrons, and behaviors of charged particles: Results of adding barium oxide concentrations

The objective of this research is to examine the effectiveness of gamma and neutron shielding, as well as to investigate the behavior of charged particles in glass compositions with the formula xBaO:5SnO2:10Na2O:10CaO:10Li2O: (65-x)SiO2. These glass compositions will be created using the melt quenching technique (MQT). The findings indicated that the physical characteristics, such as density and molar volume, exhibited a comparable pattern. The gamma-ray shielding capacity of the glass system was assessed by comparing it with theoretical, simulation, and experimental values obtained using WinXCom, PHITS (Particle and Heavy Ion Transport Code System) Monte Carlo simulation, and Compton scattering technique (CST), respectively. The results revealed that the total attenuation (μm), effective atomic number (Zeff), and electron density (Nel) exhibited a consistent increase with higher BaO contents. Additionally, this increase led to a decrease in scattering energy within the Compton energy range. The half-value layer (HVL) exhibited superior shielding characteristics compared to alternative substances. Furthermore, the addition of more BaO atoms in the glass structure results in an increased ability of the material to stop the motion of charged particles with larger mass. Conversely, lower concentrations of BaO demonstrate an efficient barrier against fast neutrons. The simulation revealed that BaO can be utilized as an additive in glass materials to enhance their radiation shielding properties in environments with high levels of radiation.

Weak signal detection based on pulse width counting method for underwater wireless optical communication with an analog mode PMT detector.

This work proposes a weak signal detection method based on pulse width counting (PWC) for the on-off keying (OOK) underwater wireless optical communication (UWOC) system with an analog mode photomultiplier tube (PMT) detector. The signal output model of the analog mode PMT in weak light communication and the influence of pulse overlap are investigated. We experimentally evaluate the proposed algorithm under different sampling rates, detection thresholds, data rates as well as received optical powers (ROPs), and compare the performance of the proposed approach with that of pulse amplitude detection and pulse peak counting. A 10-Mbps OOK UWOC link is realized with a sensitivity of -71.5 dBm in a 7-meter tank, which is 1.1-dB and 3.8-dB lower than that of pulse peak counting (PPC) and pulse amplitude detection (PAD) methods, respectively, and the total link attenuation is 94.8 dB. This system utilizes the analog mode PMT with larger dynamic range than photon-counting mode PMT to achieve weak light signal detection, which benefits design long-range UWOC systems.

Sorption and attenuation of petroleum VOCs in five unsaturated soils: Microcosms and column experiments

The fate of volatile organic compounds (VOC) vapors in the unsaturated zone is the basis for evaluating the natural attenuation potential and vapor intrusion risk. Microcosm and column experiments were conducted to study the effects chemical speciation and soil types/properties on the fate of petroleum VOCs in unsaturated zone. The biodegradation and total attenuation rates of the seven VOCs obtained by microcosm experiments in black soil and yellow earth were also generally higher than those in floodplain soil, lateritic red earth, and quartz sand. The VOC vapors in floodplain soil, lateritic red earth, and quartz sand showed slow total attenuation rates (<0.3 d−1). N-pentane, methylcyclopentane, and methylcyclohexane showed lower biodegradation rates than octane and three monoaromatic hydrocarbons. Volatilization into the atmosphere and biodegradation are two important natural attenuation paths for VOCs in unsaturated soil columns. The volatilization loss fractions of different volatile hydrocarbons in all five unsaturated soils were generally in the order: n-pentane (93.5%–97.8%) > methylcyclopentane (77.2%–85.5%) > methylcyclohexane (53.5%–69.2%) > benzene (17.1%–73.3%) > toluene (0–45.7%) > octane (1.9%–34.2%) > m-xylene (0–5.7%). The fractions by volatilization into the atmosphere of all seven hydrocarbons in quartz sand, lateritic red earth, and floodplain soil were close and higher compared to the yellow earth and black soil. Overall, this study illustrated the important roles chemical speciation and soil properties in determining the vapor-phase transport and natural attenuation of VOCs in the unsaturated zone.

Integrated photonics cascaded attenuation circuit towards single-photon detector calibration

Integrated photonics platforms are a key driver for advancing scalable photonics technologies. To rigorously characterize and calibrate on-chip integrated photodetectors for ultra-sensitive applications such as quantum sensing and photonic computing, a low-power calibration source down to single-photon levels is required. To date, such sources still largely rely on off-chip bulk or fiber optic setups to accurately attenuate a laser beam referenced to a sub-mW-level primary standard. Here, we demonstrate an on-chip integrated attenuation solution where a mW-level beam is coupled to a silicon nitride photonics circuit, and is attenuated by a series of cascaded directional couplers (DCs). With an integrated silicon photodetector, we measured an attenuation at 685 nm wavelength of up to 16.61 dB with an expanded uncertainty of 0.24 dB for one DC stage. With appropriate scattering mitigation, we infer from our results that a total attenuation of 149.5 dB (expanded uncertainty of 0.5 dB) can be obtained with 9 stages of cascaded DCs, thus allowing single-photon power levels to be obtained directly on-chip from a moderate-power laser source.

#1008 Prognostic impact of low skeletal muscle quality on 3-year mortality in initial-dialysis patients

Abstract Background and Aims Myosteatosis represents the infiltration of fat into the skeletal muscle in the early stages of sarcopenia, and has been suggested to be associated with adverse outcomes in patients undergoing dialysis. Skeletal muscle density (SMD) determined by computed tomography (CT) is commonly used to assess myosteatosis, but SMD is affected by contrast resulting in inaccurate measurements. Recently, indices for muscle quality measurements determined by muscle area have been developed. Thus, We aimed to investigate the relationship between a novel muscle area index and mortality in initial-dialysis patients and analyse variables related to myosteatosis using the cutoff values. Method This 3-year multicentric retrospective study enrolled a total of 782 initial-dialysis patients from four centres between 2014 and 2019 in China. SMD skeletal muscular area (SMA) normal attenuation muscle area (NAMA) intermuscular adipose tissue area (IMAT) was measured and skeletal muscle index (SMI) total attenuation muscle area (TAMA) NAMA/TAMA index was calculated on CT images at the level of the first lumbar vertebra. The relationship between NAMA/TAMA index and all-cause and cardiac death outcomes was analyzed. And the sex-specific optimal cut-off values of L1-NAMA/TAMA index were determined in relation to all-cause mortality. Univariate and multivariate Cox regression models were applied to evaluate potential risk factors for death. Results A total of 782 patients were enrolled. The optimal cut-off values of NAMA/TAMA index were 48.76 for males and 58.02 for females. Pearson's correlation coefficient between L1-NAMA/TAMA index and L1 SMD was 0.589 (P &amp;lt; 0.001), no significant association between L1-NAMA/TAMA index and L1 SMI was observed (P &amp;gt; 0.05), similarly, no significant association between L1 SMD and L1 SMI (P &amp;gt; 0.05). Multivariate regression analysis revealed that the low L1-NAMA/TAMA index group had lower risks of all-cause death (hazard ratio 0.988; 95% confidence interval 0.977–0.999, P = 0.041) and cardiac death (hazard ratio 3.74; 95% confidence interval 1.43–9.79, P = 0.007). Conclusion Our findings demonstrate that L1-NAMA/TAMA index acquired via CT scan is of great prognostic value on all-cause and cardiac death in patients undergoing initial-dialysis.

Analisis Kualitas Pembangunan Jaringam Fiber To The Home Iconnet Pada Area Cluster Padang Barat

Fiber To The Home (FTTH) networks have become an important communications infrastructure that meets the need for fast and reliable internet connectivity in various communities. The aim of this research is to provide a comprehensive analysis of FTTH network development, focusing on the factors that influence the quality of FTTH networks and their impact on society and industry. The research method used, among others, is quantitative by measuring the IN and OUT attenuation parameters at the Optical Distribution Point using an Optical Power Meter measuring instrument. Then the results are compared with the TIPHON/ITU-T Packet Loss standard. The analysis results show that IN and OUT attenuation greatly influences the quality of the FTTH network. The results of the total attenuation analysis on Line A show that the attenuation that has been compared using Packet Loss has a total attenuation difference of 1.11% to 1.37%, on Line B 1.07% to 1.49%, on Line C 1.27% to 1.43%, and on Line D 1.16% to 1.56% the difference obtained during the research can still be said to be quite feasible and good for use by customers. By considering these factors, it is hoped that the construction of an FTTH network can provide maximum benefits for society and industry in supporting economic growth and technological progress.

Seasonal Variation of Total Attenuation between Airborne Platform and Earth Station in South-West Region, Nigeria

The seasonal variation of total attenuation in the southwest region of Nigeria has been computed using eight (8) years dataset at Ku- and Ka-band of the transmitted power of the radar, transmitted antenna gain and the received antenna gain of the satellite retrieved from the archived of the GPM. The results obtained fluctuates between the seasons at Ku- and Ka-band. From the results obtained at Ku-and Ka-band, the results from analysis showed that the peak total attenuation was recorded between the early (MAM) and late wet (JJA) season when the intensity of rainfall is maximum in the South-West region. As a result, the effect on the airborne-earth station link will be severe which may further lead to signal outage. However, the state where the highest total attenuation was consistent is Lagos state. These seasons and Lagos state must be taking into consideration by engineers and radiowave propagation group when planning and sitting radiowave propagation in the study area.

Developed concrete reinforced by waste of lead fishing weights and steel nails as gamma rays and neutrons shields for nuclear power reactors

Wastes of steel nails WSN and wastes of lead fishing weights WLFW were successfully recycled in concrete to enhance its ability to attenuate neutrons and gamma rays. A series of studies on the effect of partially replacing coarse aggregates of concrete with different percentages (5, 10, and 20%) of WSN or WLFW on the density, slump, compressive strength, and attenuation of neutrons and gamma rays were implemented. The compressive strength of WSN-reinforced concrete ranged between 36.2 and 45.2 MPa, while that of WLFW-reinforced concrete ranged between 28.6 and 45.1 MPa. The ability of WSN- or WLFW-reinforced concrete to attenuate neutrons and gamma rays was tested by using two types of neutron energies; slow and total slow neutrons; and three gamma rays energies 661.64, 1173.23, and 1332.51 keV. Slow and total slow neutrons macroscopic cross-section, linear and mass attenuation coefficients of gamma rays, and half value layer for both types of nuclear radiation were obtained. The results showed that there is a significant improvement in the slow and total slow neutron attenuation efficiency of the considered concrete when reinforced by WSN or WLFW. On the other hand, due to the increase in the atomic number and density of both Fe present in WSN and Pb in WLFW, the attenuation ability of the studied gamma ray energies increased. The WLFW-reinforced concrete showed better value in the gamma rays and neutrons attenuation parameters compared to the WSN-reinforced concrete. Hence, the considered concretes reinforced by WSN or WLFW are a distinguished choice as radiation shields in nuclear power reactors, in addition to their adaptability to high concentrations of waste.

Estimating Kappa within a Low-Seismicity Region in Northern New Mexico Using Data Recorded by the Los Alamos Seismic Network

ABSTRACT We quantify the total attenuation, κ, and the attenuation component due to near-surface site effects, κ0, in a region in northern New Mexico using data recorded by the Los Alamos Seismic Network. The area is characterized by low seismicity, where most of the well-recorded earthquakes have magnitudes between 1 and 2. This magnitude range poses a challenge for commonly used kappa methods because the high-frequency attenuation cannot be confidently isolated from the bandwidth in which the corner frequency roll-off occurs. We determine through synthetic experiments that estimates of κ within this range have quantifiable biases that depend on source (corner frequency), site (κ magnitude), and data quality characteristics (fitting bandwidth), which can be used to correct estimated κ from three commonly used kappa methods. Using 412 recorded earthquakes, we show that a bias correction results in κ distributions and κ0 estimates that are more consistent between the three methods, suggesting that the bias correction results in κ values with higher fidelity. Using the bias-corrected κ, we find κ0 between 0.038 and 0.049 s within the Valles Caldera and between 0.026 and 0.066 s on Los Alamos National Laboratory property, values near those commonly used in the western United States. We find that a main limitation in the quality of κ0 is the small number of usable waveforms at some stations, which will to improve as more earthquakes are recorded. This contrasts with other aspects, such as fitting bandwidth and source and path variability, which are unlikely to change in the future and will ultimately be the limiting factor in κ0 resolution. Overall, our results suggest that the bias-correction scheme presented here could potentially be used in other regions where small-magnitude earthquakes are prevalent. However, future work should look to verify that bias-corrected κ estimates show consistency with those retrieved from higher magnitude earthquakes.

Radiation shielding for inertial electrostatic confinement fusion system utilizing concrete and water

In this investigation, the impact of water thickness and various types of concrete materials, each characterized by different densities and elemental compositions, is examined for their role in shielding a radiation generator based on Inertial Electrostatic Confinement Fusion (IECF) device. The study focuses on assessing several vital parameters, including the effective removal cross-section (∑Rt) for fast neutrons, total mass attenuation coefficients (μmt), linear attenuation coefficients (μl), half-value layer (HVL), and mean free path (MFP) for X-rays across different concrete types. Different water thicknesses around the IECF chamber, ranging from 0.5 to 10.0 cm, are investigated, and five concrete types are evaluated: Ilmenite-magnetite Concrete (IMC), Ordinary Concrete-1 (OC1), Barite-containing Concrete (BC), Ordinary Concrete-2 (OC2), and Serpentine-containing Concrete (SC). The results indicate that, among these materials, SC requires the least thickness to attenuate 2.45 MeV generated from IECF to 1/100th of its initial intensity across varying water thicknesses (6.5 cm in case of 5 cm water thickness). The values of μmt, HVL, and MFP are also calculated for different water thicknesses and X-ray energies (ranging from 0.2 to 3.0 MeV). These calculations highlight BC as the material requiring the least thickness to attenuate X-rays to 1/100th of their initial intensity. Moreover, neutron dose rate measurements are conducted on a commercial IECF system shielded with 50 cm of water and operated at a neutron intensity of 105 ns−1, which was ∼12 nSv/h on average, approximately 0.002% of the initial intensity. This underscores the efficacy of water shielding in attenuating the outcomes of IECF.

Mapping Ice Buried by the 1875 and 1961 Tephra of Askja Volcano, Northern Iceland Using Ground‐Penetrating Radar: Implications for Askja Caldera as a Geophysical Testbed for In Situ Resource Utilization

AbstractEruptions of the Askja Volcano in Northern Iceland in 1875 and 1961 blanketed the caldera with rhyolitic and basaltic tephra deposits, respectively, which preserved layers of seasonal snowpack as massive ice. Askja serves as an operational and geophysical analog to test ground‐penetrating radar field and analysis techniques for in situ resource utilization objectives relevant to the martian and lunar environments. We conducted ground‐penetrating radar surveys at center frequencies of 200, 400, and 900 MHz to map the thickness and extent of tephra deposits and underlying massive ice at three caldera sites. We identified up to 1 m of tephra preserving up to 4.4 m of massive ice. We measured the real dielectric permittivity of the overlying tephra and the total attenuation at each frequency of the tephra and ice. A key objective of our investigation was to determine if attenuation (or loss) could be used as an additional diagnostic signature of massive ice preserved at depth when compared to ice‐free stratigraphy. Loss rates of the ice‐rich subsurface decrease with increasing ice thickness relative to the overburden, which may constitute a possible signature. Attenuation also increased with increasing frequency. The tephra, ice, and other volcanic deposits at each of our three caldera sites and the ice‐free, pumice‐mantled 1961 Vikrahraun lava flow exhibited consistently low loss rates at all frequencies. This result highlights the ambiguity associated with identifying the unique signature of ice within low‐loss stratigraphies, a possible challenge for its identification in the martian or lunar subsurface using radar.