Multichannel Analyzer Research Articles

Characterization of an earth dam in Brazil from seismic refraction tomography and multichannel analysis of surface waves

Effective methodologies to obtain information regarding the internal features in an earth dam are fundamental for rapid and technically correct decision making. Although several geophysical methods have potential applicability for investigations on dams, the contribution of seismic methods is well known, since the P and S-waves velocities can be associated with elastic modules of geotechnical interest. The study area was the Paranoá dam, the largest dam in Brazil's federal capital. We analyzed the internal structure of the dam and identified anomalies that could be associated with water saturation. We used traveltimes tomography to obtain Vp models and the MASW method to obtain Vs models. Four profiles of seismic data were acquired downstream of the dam. Borehole's information was used to corroborate with the geophysical interpretation of the profiles. The dam's abutments and the foundation ground could be identified within most models, and the velocity values obtained were mainly related to the clay material that forms the dam's massif, with higher values associated with the quartzite rocks. The rockfill material was well marked as a low velocity zone. Saturated zones were interpreted as local anomalies of high Vp/Vs ratio. An analysis of the depth range obtained within velocity models suggests that the depth of investigation from both methodologies are likely to be site specific, rather than exclusive matter of source and receiver instrumentation.

A novel weight-drop seismic energy source for subsurface characterization

Multichannel Analysis of Surface Waves (MASW) studies for subsurface characterization in Central Ganga Basin of India, where thick cover of alluvium absorbs most of the vibrations generated by a sledgehammer source, give low quality seismic data at large offsets and generally provide imaging depth lesser than 30 m due to low quality of dispersion curves at lower frequencies. Therefore, a novel seismic energy source is designed and developed to produce large amplitude surface waves even at longer offsets and for deeper depths of imaging using dispersion analysis of surface waves. The developed source for seismic data acquisition is low-cost, repeatable, portable, and easy to operate with no environmental impact. Unlike the sledgehammer source where the quality of surface waves generated also depends on the person hitting the metal plate, the seismic data quality from the novel weight-drop source is independent of the operator.The developed source is an impact type where a free-falling mass accelerated due to gravitational pull hits onto a base plate coupled with the earth generating vibrations in the ground. The performance of the source was evaluated in a field trial. A receiver array of 24-channel cabled geophones with 3 m spacing was planted on the ground. Seismic data were acquired using the source at 5 m negative offset inline from the first geophone. Seismic data were also recorded with the sledgehammer as a source for comparison. Five shot gathers for each source were acquired with the same acquisition geometry and source position.Shot gathers were analyzed and compared using trace attributes, 1D and 2D Fourier spectra, signal-to-noise ratio, relative energy, and dispersion images. The study shows that the developed source produces low frequency high amplitude signal and better dispersion image, notably in the lower frequency range, in comparison with the sledgehammer source. Therefore, the developed source is adapted to investigate deeper subsurface velocity structure with dispersion curve from high amplitude surface wave analysis. Moreover, the repeatability study suggests that the repeat shot gathers acquired from the developed source have remarkably high degree of similarity. Therefore, seismic data acquisition with the developed source does not require repeat shots for vertical stacking as often done in case of a hammer source. Sound pressure level measurement indicates that the developed source has no adverse environmental impact on the operator. From the field trial of the developed source, it is convinced that the source is cost-effective, portable, easy to operate and handle and is environmentally friendly.

Environmental Radioactivity Concentrations and Assessment of Radiological Hazards in Soil Around Bandung Nuclear Area

Bandung nuclear area is an area which is nuclear reactor named TRIGA 2000 and research laboratory located. The reactor and research laboratory are utilized for training, researching and radioisotopes production that has potential to contaminate the environment. Environmental radioactivity monitoring is done periodically to find out potential radioactive release from activities inside Bandung nuclear area to surroundings. However, the assessment of radiological hazards to determine the potential radiological dangers to humans and environment around Bandung nuclear area is not done yet. The objective of this study is assessing the radiological hazards in Bandung nuclear area by comparing the data from soil samples taken in environment radiological monitoring activity with the recommendation data based on UNSCEAR and other references to find out the radiological hazards that potentially affect to humans, where this assessment has never been carried out in this area. The assessment of radiological hazards in this study is limited to Ra-226, Th-232 and K-40 nuclides because contributing to radiation dose received by human. The study was conducted by collecting soil samples from several sampling points inside and outside Bandung nuclear area. Then, the nuclides of Ra-226, Th-232 and K-40 contained in soil samples are measured by using the gamma-ray spectrometry method with high resolution detector that is HPGe (High Purity Germanium) and a computer-based Multichannel Analyzer (MCA). The results indicated that the concentration of environmental radioactivity ranged between 11.02 to 32.66 Bq/kg for Ra-226; 19.44 to 43.83 Bq/kg for Th-232 and 56.00 to 183.39 Bq/kg for K-40. This study also obtained results that the radiological hazard of the gamma dose rate ranged from 23.54 to 40.23 nGy/h, the radium equivalent was 51.77 to 89.78 Bq/kg; the external hazard index was 0.14 to 0.24 and the internal from 0.18 to 0.33; the index of radioactivity level was 0.37 to 0.63. The annual effective dose equivalent for outdoor ranged from 0.03 to 0.05 mSv/y and indoor was 0.12 to 0.20 mSv/y. The lifetime cancer risk for outdoors ranged from 0.10x10–3 to 0.17x10–3 and indoor was 0.4x10–3 to 0.69x10–3. The values of radiological hazard were below the international requirements. There is no potential risk of natural radiation of gamma ionizing radiation exposure in soil samples around the Bandung nuclear area for workers, the public, and the environment.Keywords: Environment, Radiological, Hazard, Gamma, Spectrometry.

Importance of the lysine cluster in the translocation of anions through the pyrophosphate specific channel OprO

Pseudomonas aeruginosa is a Gram-negative bacterium with an intrinsic resistance towards antibiotics due to the lack of a large diffusion pores. Exchange of substances with the environment is done mainly through a set of narrow and substrate-specific porins in its outer membrane that filter molecules according to their size and chemical composition. Among these proteins are OprP and OprO involved in the selective uptake of mono- and pyrophosphates, respectively. Both proteins are homotrimers and each monomer features an hourglass-shaped channel structure including a periplasmic cavity with a lysine cluster. In this study, we focus on the characterization of this lysine cluster in OprO. The importance of these lysine residues was shown with alanine substitutions in single channel conductance experiments, by titration of mono- and pyrophosphate in multi-channel analysis and by molecular dynamics simulations. All obtained data demonstrated that the closer the mutated lysine residues are to arginine 133, the lower gets the single channel conductance. It was found that the ion flow through each monomer can follow two different lysine paths indicating that phosphate ions have a larger freedom on the periplasmic side of the constriction region. Our results emphasize the important role of the lysine residue 121 in the binding site together with arginine 133 and aspartic acid 94. An improved understanding of the ion mobility across these channels can potentially lead to an optimized permeation of (phosphonic acid containing) antibiotics through the outer membrane of P. aeruginosa and the development of new drug molecules.

In-situ investigation on coal mine overburden dump slope and its seismic stability considering heterogeneity

Stability of the coal mine overburden (OB) dump slopes is many times compromised owing to the lesser availability of the in-situ characteristics of the OB dump materials and their spatial heterogeneity. In this study, multi-channel analysis of surface waves (MASW) investigation was carried out for the characterization of OB dump materials of Jambad opencast coal mine of India and the variation of heterogeneous in-situ characteristics has been reported in terms of statistical parameters. Next, the stability of a two-bench OB dump slope against seismic forces was investigated through finite element limit analyses coupled with random field theory utilizing Karhunen-Loeve expansion method for the spatial heterogeneity of the OB dump material. The effects of spatial heterogeneity of the OB dump material on the probability of failure and the critical pseudostatic seismic coefficient of the slope were investigated through Monte-Carlo simulations. The influence of spatial heterogeneity of OB dump materials were investigated with both isotropic and anisotropic correlation lengths. Finally, seismic slope stability analyses were also carried out using the discrete element method for the size heterogeneity of the OB dump materials. This study summarizes the effects of heterogeneity of material property and size on the seismic stability of OB dump slope.

Vs30 Structure of Almeria City (SE Spain) Using SPAC and MASW Methods and Proxy Correlations

The topographic slope method is an innovative, fast and very low-cost technique for estimating the average S-wave velocity in the upper 30 m (Vs30) based on the relationship between this quantity and the slope of the ground, obtained using a Digital Elevation Model (DEM). The method is based on the good linear correlations log(Vs30)–log(slope) found experimentally, which, ideally, should be determined for each region. If measured Vs30 data are not available to carry out this fitting for the study area, correlations from other areas could be used, although the reliability of the estimated Vs30 results would be lower. In this article, Vs30 observations are made for the city of Almeria, using Spatial Autocorrelation Surveys (SPAC) and Multichannel Analysis of Surface Waves (MASW), obtaining two types of fitting: (a) linear relationship log(Vs30)–log(slope); and (b) considering additional dependence on geological units. The reliability, evaluated by Multiple R-Squared (MRS), varies between 79.2% in the first case and 87.0% in the second, lowering the mean absolute values of the residuals at the observation points in the first case from 40.0 m/s to 29.0 m/s. Using a more generic correlation obtained for other areas of the world, the mean absolute residuals increase to 74.7 m/s.

Multi-channel data fusion and intelligent fault diagnosis based on deep learning

In complex manufacturing systems, multi-channel sensor data are usually recorded for fault detection and diagnosis. Most existing multi-channel data processing methods adopt tensor analysis technology, which cannot effectively describe the temporal and spatial structures of the multi-channel data. The obstacles in multi-channel data analysis are the temporal correlation between the time-series data of the single-channel and the spatial correlation between different channels. In this paper, a novel deep convolutional neural network model is proposed for multi-channel data fusion and intelligent fault diagnosis. First, features of the multi-channel data are extracted from two scales. The extracted features are then fused through a multi-layer neural network. Finally, a classifier of fault modes is established by using the improved Softmax function. The fault diagnosis performance of the proposed model is evaluated and compared with other common methods in both the simulation studies and real-world case studies. Results show that the proposed methodology has superior fault diagnosis performance for multi-channel data.

Analysis of Subsurface Layers using the Multichannel Analysis of Surface Waves Method in Manimbahoi, Gowa Regency

This research is about the structure of the soil layer at the research site in Manimbahoi, Parigi District, Gowa Regency. This research is very important considering that the location has experienced a mega landslide which resulted in some residents being not found. This study aims to provide an overview of the shallow soil layer at the landslide disaster location. This study uses one of the geophysical methods, Multichannel Analysis of Surface Waves (MASW) method, with 4 lines at points at the landslide location. Based on the results of the study, the velocity of the Vs30 wave was obtained in each line. On the first line the velocity of Vs30 is 303.5 m/s. On the second line the velocity of Vs30 is 284.1 m/s. On the third line the velocity of Vs30 is 309.0 m/s. On the fourth line the velocity of Vs30 is 256.1 m/s. Based on the soil classification by looking at the Vs30 velocity, it can be determined that the type of soil at the research location is medium soil (sand). Medium soil is unconsolidated sediment, described as soil composed of minerals that are not compact

Groundwater Response to Tide Fluctuation and Rainfall in Coastal Reclamation Area

Abstract Land reclamation not only provides valuable space for urban development, but also creates an upper aquifer in fill materials. Analysis of groundwater level (GWL) fluctuations in coastal aquifer formed due to land reclamation can provide important insight into the groundwater system (GWS) evolution, including the connectivity between the GWL and influencing variables (ocean tide and rainfall). This study presents wavelet analysis, multichannel SSA-wavelet analysis (MSSA-WA), and lag correlations to analyze the response of GWL to ocean tide and rainfall in the reclamation area of Zhoushan Island, China. The MSSA-WA results and the lag correlations show that the MSSA-WA provides better analysis results, specifically, clay layer and rainfall filtered information. The influence of the influencing variables on the upper GWL is relatively greater than the clay layer, and rainfall has a relatively stronger impact on GWLs than tides. The GWLs of the upper layer, SW18 and SW21, which are heavily influenced by influencing variables, can be predicted through variations in influencing variables. Finally, the analysis of the results shows that the lithology of different aquifers, offshore distance, preferential flow path, and pressure load can be factors between tides and GWLs. For rainfall and GWLs, different lithology of aquifers, properties of vadose zone, and topography can be influential factors. The combination method provides an optimization method for GWL fluctuations in coastal reclamation area with combined MSSA and wavelet analysis for correlation analysis between GWL and influencing variables (ocean tide and rainfall) and analysis of corresponding causes and influencing factors.

Shallow shear wave velocity structure of the Dongshan sag area using surface wave data in a deep reflection profile of the Yuanmou area of Yunnan province, China

Deep reflection seismic data contain abundant surface wave information for which the velocity structure in the near-surface shallow underground can be obtained using multichannel analysis of surface waves (MASW). This paper uses the MASW method to process deep reflection data in the Yuanmou area in Yunnan province, China. The MASW method uses the phase velocity spectral transformation of Rayleigh waves to obtain its dispersion curve. The initial model for different lithology classifications is established to invert the underground velocity structure. This study obtains a two-dimensional shear wave velocity structure profile to investigate the shear wave velocity structure. Generally, the study results have shown that the shear wave velocity structure obtained by the MASW method corresponds well with the surface conditions and accurately reflects faults' changes, folds, and lithology. Moreover, the formation sand content calculation shows a large difference in Dongshan sag's formation sand content. The sand contents of Cretaceous and Middle Jurassic strata are over 30% similar, and the sandstone content of underlying Early Jurassic strata is mostly 30% lower. The stratum buried depth of Early Jurassic strata is between 0– 800 m. The dip angle of LZJF at this location is 90°. The west side of the LZJF is based on Proterozoic uplift, and the Quaternary sedimentary thickness exceeds 300 m above the uplift stratum. Whereas on the east side of the LZJF, the stratum of the Dongshan sag section is mainly a synclinal structure.

Investigation of site properties of the Çaldıran (Van, Eastern Turkey) settlement area using surface wave and microtremor methods

Çaldıran (Van, eastern side of Turkey) which is a seismically very active region has more than active faults around and the areas under active tectonic effect. The earthquakes and soil characteristics are the significant factors that increase the severity of the damages ratio. For this reason, the characteristics of the engineering structure should be defined accurately and reliably. The shear wave velocity (Vs) obtained from geophysical methods is one of the most important parameters that determine the behavior of the soil during an earthquake. In this study, active and passive source surface wave methods were applied at different measurement points in the study area in order to determine soil properties of the settlement area and its surroundings in Çaldıran district the city of Van. As part of this study, 80 boreholes, 95 multichannel analysis of surface wave (MASW) profiles, and 66 microtremor (HVSR) measurements were performed in the study area. The Vs velocity with depth dependent could be determined by using the dispersive behavior of Rayleigh waves in surface wave analysis methods. In order to analyze the engineering characteristic of the region and earthquake-soil-structure relations parameters such as the amplification factor, predominant period (t0), Vs velocity, average velocity up to 30 m Vs30, and seismic vulnerability index (Kg) maps have been prepared. In order to reveal the variety of the engineering properties of the area in horizontal and vertical directions, depth cross-sections in different directions were created. When the tectonic structure and regional geology were examined, it was determined that all profile results were compatible with the geological structure.

Integrated 2D beam emission spectroscopy diagnostic at the Huan-Liuqi-2A (HL-2A) tokamak.

Two newly developed, eight-channel, integrated Beam Emission Spectroscopy (BES) detectors have been installed at Huan-Liuqi-2A tokamak, which extends the existing 16 single-channel modular BES system with additional 16 spatial channels. The BES collects the Doppler-shifted Balmer Dα emission with a spatial resolution of 1cm (radial) × 1.5cm (poloidal) and a temporal resolution of 0.5 µs to measure long-wavelength (k⊥ρi < 1) density fluctuations. Compared to the modular BES, the dark noise of the integrated BES is reduced by 50%-60% on average. The signal-to-noise ratio of the integrated BES system is optimized by the high light throughput front-end optics, high quantum efficiency photodiodes, high-gain, low-noise preamplifiers, and sufficient cooling capacity provided by the thermoelectric cooling (TEC) units that maintain the detectors at -20 °C. Crosstalk between channels that share the same optical system is found to be negligible. High-quality density fluctuation data enables 2D (radial-poloidal) imaging of turbulence, which allows for multi-channel spectral analysis, multi-channel cross-correlation analysis and velocimetry analysis. Preliminary results show that BES successfully captures the spatiotemporal features of the local turbulence and obtains statistically consistent turbulence characterization results.

Simultaneous deblending and source reconstruction for compressive 3D simultaneous-source acquisition data via interpolated multichannel singular spectrum analysis

Iterative rank reduction implemented via multichannel singular spectrum analysis (MSSA) filtering has been proposed for data deblending. The original algorithm is based on the projected gradient-descent method with a projection given by the MSSA filter. Unfortunately, MSSA filters operate on data deployed on a regular grid. We have developed a way to adopt a recently proposed modification to MSSA, interpolated-MSSA, to deblend and reconstruct sources in situations in which the acquired blended data correspond to sources with arbitrary irregular-grid coordinates. In essence, we develop an iterative rank-reduction deblending method that can honor true source coordinates. In addition, we indicate how the technique also can be used for source regularization and interpolation. We compare our algorithm with traditional iterative rank reduction that adopts a regular source grid and ignores errors associated with allocating off-the-grid source coordinates to the desired output grid. Synthetic and field data examples indicate how our method can deblend and reconstruct sources simultaneously.

A combined GA and DLS parallel algorithm for multimode Rayleigh wave inversion

Multichannel analysis of surface waves (MASW) is a vital method in near-surface exploration. Linear algorithms, such as damped least square method (DLS), are highly dependent on the initial model and are prone to trapping in local minima. While nonlinear algorithms such as genetic algorithm (GA) are globally optimal but inefficient, they are not very practical for complex calculations.In this paper, we propose a combined GA and DLS parallel algorithm (GA-DLS), which has a global search capability due to the GA framework, and has a quick local search capability due to the DLS parallel computing. To simulate the earth model in complex near-surface conditions, we set a low-velocity layer among a layered earth model (LVL) and a high-velocity layer among a layered earth model (HVL), we perform the inversion with DLS, GA, and GA-DLS, respectively. The comparison shows that the GA-DLS inversion gets an efficient and accurate result. Finally, we use the GA-DLS algorithm to invert the field data and achieve good results, verifying the effectiveness of the algorithm.

Wearable bioelectronic masks for wireless detection of respiratory infectious diseases by gaseous media

Respiratory infectious diseases (H1N1, H5N1, COVID-19, etc.) are pandemics that can continually spread in the air through micro-droplets or aerosols. However, the detection of samples in gaseous media is hampered by the requirement for trace amounts and low concentrations. Here, we develop a wearable bioelectronic mask device integrated with ion-gated transistors. Based on the sensitive gating effect of ion gels, our aptamer-functionalized transistors can measure trace-level liquid samples (0.3 μL) and even gaseous media samples at an ultra-low concentration (0.1 fg/mL). The ion-gated transistor with multi-channel analysis can respond to multiple targets simultaneously within as fast as 10 min, especially without sample pretreatment. Integrating a wireless internet of things system enables the wearable mask to achieve real-time and on-site detection of the surrounding air, providing an alert before infection. The wearable bioelectronic masks hold promise to serve as an early warning system to prevent outbreaks of respiratory infectious diseases.

Blind field tests to determine Rayleigh wave velocity on a high-speed railway environment: The reliability of seismic surface waves methods

To ensure track stability and good earthwork performance for high-speed railways the surface wave velocity in the earthworks should exceed the train’s speed. Specifications for high-speed rail are now stating minimum Rayleigh wave (VR) velocities to be checked during construction. This requires suitable reliable geophysical tests, however there are no defined standards or data collection and processing protocols. Additionally, the analysis of these data traditionally relies on the practice and experience of those undertaking the work which can introduce variability in results.This paper presents the results of a blind comparison trial investigating Multichannel Analysis of Surface Waves test (MASW) for use in high-speed rail earthworks compliance evaluation, concentrating on assessment of Rayleigh wave velocity (VR). Testing was undertaken by four companies, at the same site on natural ground and a stabilised trial embankment. Defined tests protocols and a test of their own design against a specification to assess VR were used. The anonymised VR results show reasonable agreement in the dispersive character of the soil if higher modes are carefully considered when picking a dispersion curve. The VR results were then investigated against depth using a rule of thumb. Such an approach avoids the inversion processing step (to get more traditional Vs against depth) which potentially introduces variability. This suggests that direct Rayleigh wave data could be used by earthworks engineers to give routine compliance assessment and then if required further investigation undertaken in areas of compliance concern within the overall earthwork.

Multi-Channel Metabolomics Analysis Identifies Novel Metabolite Biomarkers for the Early Detection of Fatty Liver Disease in Dairy Cows.

Fatty liver disease, a type of metabolic disorder, frequently occurs in dairy cows during the parturition period, causing a high culling rate and, therefore, considerable economic losses in the dairy industry owing to the lack of effective diagnostic methods. Here, metabolite biomarkers were identified and validated for the diagnosis of metabolic disorders. A total of 58 participant cows, including severe fatty liver disease and normal control groups, in the discovery set (liver biopsy tested, n = 18), test set (suspected, n = 20) and verification set (liver biopsy tested, n = 20), were strictly recruited and a sample collected for their feces, urine, and serum. Non-targeted GC-MS-based metabolomics methods were used to characterize the metabolite profiles and to screen in the discovery set. Eventually, ten novel biomarkers involved in bile acid, amino acid, and fatty acid were identified and validated in the test set. Each of them had a higher diagnostic ability than the traditional serum biochemical indicators, with an average area under the receiver operating characteristic curve of 0.830 ± 0.0439 (n = 10) versus 0.377 ± 0.182 (n = 9). Especially, combined biomarker panels via different metabolic pipelines had much better diagnostic sensitivity and specificity than every single biomarker, suggesting their powerful utilization potentiality for the early detection of fatty liver disease. Intriguingly, the serum biomarkers were confirmed perfectly in the verification set. Moreover, common biological pathways were found to be underlying the pathogenesis of fatty liver syndrome in cattle via different metabolic pipelines. These newly-discovered and non-invasive metabolic biomarkers are meaningful in reducing the high culling rate of cows and, therefore, benefit the sustainable development of the dairy industry.

On the measurement uncertainty of microdosimetric quantities using diamond and silicon microdosimeters in carbon-ion beams.

The purpose of this paper is to compare the response of two different types of solid-state microdosimeters, that is, silicon and diamond, and their uncertainties. A study of the conversion of silicon microdosimetric spectra to the diamond equivalent for microdosimeters with different geometry of the sensitive volumes is performed, including the use of different stopping power databases. Diamond and silicon microdosimeters were irradiated under the same conditions, aligned at the same depth in a carbon-ion beam at the MedAustron ion therapy center. In order to estimate the microdosimetric quantities, the readout electronic linearity was investigated with three different methods, that is, the first being a single linear regression, the second consisting of a double linear regression with a channel transition and last a multiple linear regression by splitting the data into odd and even groups. The uncertainty related to each of these methods was estimated as well. The edge calibration was performed using the intercept with the horizontal axis of the tangent through the inflection point of the Fermi function approximation multi-channel analyzer spectrum. It was assumed that this point corresponds to the maximum energy difference of particle traversing the sensitive volume (SV) for which the residual range difference in the continuous slowing down approximation is equal to the thickness of the SV of the microdosimeter. Four material conversion methods were explored, the edge method, the density method, the maximum-deposition energy method and the bin-by-bin transformation method. The uncertainties of the microdosimetric quantities resulting from the linearization, the edge calibration and the detectors thickness were also estimated. It was found that the double linear regression had the lowest uncertainty for both microdosimeters. The propagated standard (k = 1) uncertainties on the frequency-mean lineal energy and the dose-mean lineal energy values from the marker point, in the spectra, in the plateau were 0.1% and 0.2%, respectively, for the diamond microdosimeter, whilst for the silicon microdosimeter data converted to diamond, the uncertainty was estimated to be 0.1%. In the range corresponding to the 90% of the amplitude of the Bragg Peak at the distal part of the Bragg curve (R90 ) the uncertainty was found to be 0.1%. The uncertainty propagation from the stopping power tables was estimated to be between 5% and 7% depending on the method. The uncertainty on the and coming from the thickness of the detectors varied between 0.3% and 0.5%. This article demonstrate that the linearity of the readout electronics affects the microdosimetric spectra with a difference in values between the different linearization methods of up to 17.5%. The combined uncertainty was dominated by the uncertainty of stopping power on the edge.

Characterization of the shallow subsurface structure across the Carrascoy Fault System (SE Iberian Peninsula) using P-wave tomography and Multichannel Analysis of Surface Waves

The seismicity in the SE Iberian Peninsula is distributed parallel to the coast in a well-developed strike-slip fracture system known as the Eastern Betic Shear Zone (EBSZ). This work focuses on the characterization of the shallow subsurface structure of the Algezares-Casas Nuevas Fault, within the Carrascoy Fault System of the EBSZ. The Carrascoy Fault borders the Guadalentín Depression to the south, which is a densely populated area with extensive agricultural activity. Therefore, this faults system represents a seismic hazard with significant social and economic implications. We have constructed two velocity-depth models based on P-wave tomography and Multichannel Analysis of Surface Waves (MASW) acquired from seismic reflection data. The resulting velocity models have allowed us to interpret the first ~250m depth and have revealed: i) the thickness of the critical zone; ii) the geometry of the Algezares-Casas Nuevas Fault; iii) the depth of the Messinian/Tortonian contact and iv) the presence of blind thrusts and damage zones under the Guadalentín Depression. Our results have also helped us to estimate an apparent vertical slip rate of 0.66±0.06m/ky for the Algezares-Casas Nuevas Fault since 209.1±6.2ka. Our results provide a methodological and backflow protocol to study the shallow subsurface of active faults, complementing previous geological models based on paleoseismological trenches, and can be used to improve the seismic hazard assessment of tectonically active regions around the world.

Thermal hydraulic modeling of solid-fueled nuclear thermal propulsion reactors part II: Full-core coupled neutronic and thermal hydraulic analysis

This paper focuses on the extension and application of the previously validated thermal–hydraulic engineering code ntpThermo to perform multi-channel analysis for full-core coupled neutronic and thermal–hydraulic simulations. This paper also introduces the Basilisk code, which enables coupled full-core neutronic and thermal–hydraulic simulations by integrating Serpent, the continuous energy Monte-Carlo neutron transport code, and ntpThermo within a flexible object-oriented framework. Today, limited data exists pertaining to coupled multiphysics analysis of low-enriched uranium nuclear thermal propulsion reactors. More specifically, the impact of thermal–hydraulic feedback on the neutronic solution for full core applications is not well quantified. In this paper full-core coupled neutronic and thermal–hydraulic simulations are performed to ascertain the importance of thermal–hydraulic feedback on the predicted reactivity and local power distributions. The reactor design analyzed adheres to the current industry ground rules in an effort to provide useful insights for the current industry design effort. The results in this paper demonstrate that thermal–hydraulic feedback must be considered to accurately predict reactivity; otherwise, errors on the order of hundreds to thousands of pcms can be observed. Additionally, neglecting thermal–hydraulic feedback can trigger inconsistencies between the radial power distribution and the fuel orificing pattern. A design approach that doesn’t account for thermal–hydraulic feedback can lead to a final design that may experience thermal failure via excessive fuel temperatures, and would require a reduction of reactor power. The latter will cause a subsequent decrease in exit propellant temperatures and thus specific impulse of the rocket engine. Sensitivity studies were conducted to determine the importance of specific thermal–hydraulic fields and revealed that the local moderator temperature has a notable impact on the local power distributions.