Total Attenuation Research Articles

Quantitative ultrasound, elastography, and machine learning for assessment of steatosis, inflammation, and fibrosis in chronic liver disease.

To develop a quantitative ultrasound (QUS)- and elastography-based model to improve classification of steatosis grade, inflammation grade, and fibrosis stage in patients with chronic liver disease in comparison with shear wave elastography alone, using histopathology as the reference standard. This ancillary study to a prospective institutional review-board approved study included 82 patients with non-alcoholic fatty liver disease, chronic hepatitis B or C virus, or autoimmune hepatitis. Elastography measurements, homodyned K-distribution parametric maps, and total attenuation coefficient slope were recorded. Random forests classification and bootstrapping were used to identify combinations of parameters that provided the highest diagnostic accuracy. Receiver operating characteristic (ROC) curves were computed. For classification of steatosis grade S0 vs. S1-3, S0-1 vs. S2-3, S0-2 vs. S3, area under the receiver operating characteristic curve (AUC) were respectively 0.60, 0.63, and 0.62 with elasticity alone, and 0.90, 0.81, and 0.78 with the best tested model combining QUS and elastography features. For classification of inflammation grade A0 vs. A1-3, A0-1 vs. A2-3, A0-2 vs. A3, AUCs were respectively 0.56, 0.62, and 0.64 with elasticity alone, and 0.75, 0.68, and 0.69 with the best model. For classification of liver fibrosis stage F0 vs. F1-4, F0-1 vs. F2-4, F0-2 vs. F3-4, F0-3 vs. F4, AUCs were respectively 0.66, 0.77, 0.72, and 0.74 with elasticity alone, and 0.72, 0.77, 0.77, and 0.75 with the best model. Random forest models incorporating QUS and shear wave elastography increased the classification accuracy of liver steatosis, inflammation, and fibrosis when compared to shear wave elastography alone.

Can Forest Fires Be an Important Factor in the Reduction in Solar Power Production in India?

The wildfires over the central Indian Himalayan region have attracted the significant attention of environmental scientists. Despite their major and disastrous effects on the environment and air quality, studies on the forest fires’ impacts from a renewable energy point of view are lacking for this region. Therefore, for the first time, we examine the impact of massive forest fires on the reduction in solar energy production over the Indian subcontinent via remote sensing techniques. For this purpose, we used data from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIPSO), the Satellite Application Facility on support to Nowcasting/Very Short-Range Forecasting Meteosat Second Generation (SAFNWC/MSG) in conjunction with radiative transfer model (RTM) simulation, in addition to 1-day aerosol forecasts from the Copernicus Atmosphere Monitoring Service (CAMS). The energy production during the first quarter of 2021 was found to reach 650 kWh/m2 and the revenue generated was about INR (Indian rupee) 79.5 million. During the study period, the total attenuation due to aerosols and clouds was estimated to be 116 and 63 kWh/m2 for global and beam horizontal irradiance (GHI and BHI), respectively. The financial loss due to the presence of aerosols was found to be INR 8 million, with the corresponding loss due to clouds reaching INR 14 million for the total Indian solar plant’s capacity potential (40 GW). This analysis of daily energy and financial losses can help the grid operators in planning and scheduling power generation and supply during the period of fires. The findings of the present study will drastically increase the awareness among the decision makers in India about the indirect effects of forest fires on renewable energy production, and help promote the reduction in carbon emissions and greenhouse gases in the air, along with the increase in mitigation processes and policies.

Noise attenuation varies by interactions of land cover and season in an urban/peri-urban landscape.

Anthropogenic noise is increasing worldwide because of growing human populations, transportation, and resource extraction. This excessive noise negatively impacts humans and wildlife. To mitigate noise pollution, the use of vegetation in urban planning is becoming increasingly common. However, noise attenuation can be influenced by poorly understood differences in land cover and seasonality that exist across complex urban and peri-urban environments. We compared the noise attenuation capacity of sites typifying dominant land covers in southern Ontario, Canada (forest, tallgrass prairie, and agriculture) across three seasons (summer, fall, and winter). We found that total noise attenuation was affected by a complex interaction of both site and season across low (250 Hz), mid (500 Hz), and high (1000 Hz) frequency sound. Seasonal changes in vegetation density varied between sites and seemed to play only a partial role in total noise attenuation. While forest, trees, and shrubs continue to be effective for managing noise pollution, our results suggest that other types of land cover can also be useful (e.g., tallgrass prairie). With growing interest in the potential noise attenuating capabilities of vegetation, we recommend further consideration of the seasonal variation in attenuation that can occur across the diverse land covers of urban and peri-urban environments.

Influence of obesity in interstitial lung disease associated with anti-aminoacyl-tRNA synthetase antibodies

BackgroundObesity is a major risk factor for developing various respiratory diseases. Patients with anti-aminoacyl tRNA synthetase (ARS) antibodies often have interstitial lung disease (ILD). The present study was conducted to evaluate the association between obesity and outcomes of anti-ARS antibody-related ILD (ARS-ILD). MethodsWe retrospectively investigated 58 patients with ARS-ILD and compared the clinical characteristics, treatment, and prognoses between obese (body mass index [BMI] ≥25 kg/m2) and nonobese (BMI <25 kg/m2) patients. Chest fat was quantified via computed tomography (CT). Thoracic subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) were measured at diagnosis and first relapse of ILD. ResultsSixteen patients were obese. Obese patients had lower percentages of predicted diffusing capacity of the lungs for carbon monoxide and higher high-resolution CT scores and SAT and VAT indexes than did nonobese patients. The ILD relapse rate was higher in obese patients (P < 0.01), especially among those with high SAT indexes (P < 0.01). The SAT and VAT indexes increased significantly from diagnosis until first relapse. Among clinical parameters at first relapse, SAT and VAT indexes were correlated with serum Krebs von den Lungen‐6 levels (r = 0.720, P = 0.008) and total ground-glass attenuation scores (r = 0.620, P = 0.024), respectively. ConclusionsObesity and high SAT indexes are risk factors for ILD relapse in patients positive for anti-ARS antibodies. Evaluating and quantifying patients’ chest fat on CT is important for predicting ILD relapse.

Search for Tissue Equivalent Materials Based on Exposure and Energy Absorption Buildup Factor Computations

Tissue equivalent materials (TEM) are frequently used in research as a means to determine the delivered dose to patients undergoing various therapeutic procedures. They are used in routine quality assurance and quality control procedures in diagnostic and therapeutic physics. However, very few materials that are tissue equivalent have been developed for use in research at the low photon energies involved in diagnosis radiology. The objective of this study is to describe a series of TEMs designed to radiographically imitate human tissue at diagnostic photon energies. TEMs for adipose, cortical bone, fat, lung, and muscle tissues were investigated in terms of energy absorption and exposure buildup factors for photon energy range 15–150 keV and for penetration depths up to 40 mean free path. BUF was computed based on GP-fitting method. Moreover, we also compared some radiological properties, including the total attenuation and the energy-absorption attenuation, the effective atomic number, and the CT number at 30, 100, and 120 kVp. We found that SB3, Glycerol trioleate, and MS15 perfectly mimic cortical bone, fat, and muscle tissues, respectively. Additionally, AP6 and Stracey latex are good TEM for adipose and lung tissues, respectively. The results of this work should be useful in radiation diagnosis and dosimetry applications for the large physician researcher community.

Control attenuation and temporary immunity in a cellular automata SEIR epidemic model

Mathematical modeling is an important tool to analyze impacts and plan to mitigate epidemics in communities. In order to estimate the impact of control measures in a second wave of infections, we analyze the SEIR epidemic model based on stochastic cellular automata. The control measure is based on one of the key strategies to control the epidemic, which is the restriction of the mobility of individuals in space. For stronger restrictions, we observe a decrease larger than 15% in the total number of infected individuals during the epidemic. On the other hand, the total attenuation of control measures in the system can lead to a second wave scenario and even a situation in which the total number of infected individuals is close to the uncontrolled case. Additionally, we also include the possibility of reinfection, as the SEIRS model, where the recovered individuals can go to the susceptible state based on a fixed immunity time or a probabilistic rule. Our results show that an extinction of the epidemic occurs only for a fixed immunity time.

Evaluation of ultrasonic scattering in agar-based phantoms using 3D printed scattering molds.

Acoustic characterization of tissue mimicking materials in terms of attenuation, absorption, scattering and propagation velocity is essential for their utilisation in experiments, thus sparing the need for living tissues or cadavers. Although there is a vast literature regarding the acoustic characterization of such materials in terms of attenuation or propagation velocity, there is limited data regarding the quantification of the scattering coefficient. Herein stimulated the utilisation of four agar-based phantoms featuring different sizes of scattering agar-structures on one of their surfaces so as to provide experimental evaluation of the magnitude of scattering. The agar-based phantoms were developed with 6% w/v agar and 4% w/v silica and featured scatterers of sizes of 0-1mm. The acoustic properties of propagation speed, impedance, insertion loss and attenuation were evaluated utilising the pulse-echo and through-transmission techniques. Scattering was deduced from the data. The propagation speed measured at 2.7MHz was in the range of 1531.23-1542.97m/s. Respectively the attenuation as measured at 1.1MHz was in the range of 1.216-1.546dB/cm increasing with increased scatterer size. Respectively the scattering coefficient was in the range of 0.078-0.324dB/cm. Moreover, the scattering coefficient was linearly dependent on frequency in the range of 0.8-2.1MHz indicating a 6-23% effect of the total attenuation. The experimental results demonstrate the utilisation of the procedure for quantification of the scattering coefficient of tissue mimicking materials thus improving the diagnostic and therapeutic uses of ultrasound.

Estimating Effect of Total Specific Atmospheric Attenuation on Performance of FSO Communication Link in South Africa

In comparison with Radio Frequency (RF), the Free Space Optical Communication (FSOC) provides higher bandwidth, free license operation, and less initial expenditure. However, its susceptibility to changes in atmospheric weather conditions. In this paper, the impact of irradiance fluctuation on FSO systems was estimated using Rytov theory for major cities in South Africa. The extent to which the refractive index structure parameter, propagation distance and link margin affect the optical signal power at the receiver is discussed and the different methods used in evaluating the atmospheric turbulence effect are investigated. In order to achieve the stated aim, meteorological data, altitude, visibility, and wind speed were obtained from the archive of South Africa Weather Services for a period of 3years (2016-2018) over seven locations which include Cape Town, Pretoria, Upington, Bloemfontein, Emalahleni, Polokwane, East London. Results show that Emalahleni was found to possess the poor visibility of 4.4 km because of foggy conditions due to the activities of miners and other environmental factors, followed by East London with average visibility of 4.8 km. From the analysis of link margin, it was shown that FSO link attenuation reduces at higher wavelengths and long link distances due to the effect of geometric and atmospheric losses. The results show that the rate of decrease in link margin is much higher in the inland regions as compared to the coastal regions; therefore, FSO systems are prone to outage during high rainfall and longer range of connections.

Harmonic Detection for Active Power Filter Based on Two-Step Improved EEMD

The performance of active power filter (APF) mainly depends on its harmonic detection method. Empirical mode decomposition (EMD) is applied to APF because of its effectiveness for any complicated signal analysis. Ensemble empirical mode decomposition (EEMD) can suppress mode mixing caused by EMD to a certain extent, but the amplitude and energy of fundamental is severely attenuated. To solve this problem, in this article, the causes of attenuation are discussed from the perspective of intrinsic mode functions (IMFs) energy, and an approach based on two-step improved EEMD is proposed. The first improved step (FI-EEMD) is to suppress the mode mixing and fundamental attenuation by injecting white noise and analytical signal with determined parameters into the target signal. The parameters of the analytical signal are selected according to the power grid conditions and signal characteristics. The second improved step (SI-EEMD) puts forward a signal reconstruction method based on the distribution of IMF energy extreme points and the distinguishing law of signal and noise to reduce the influence of noise-dominated components. The results show that the two-step improved EEMD not only has high-quality extracted fundamental with low total harmonic distortion (THD) and energy attenuation, but also has good applicability to aperiodic and nonstationary signals, which greatly improve the harmonic detection accuracy of APF.

Investigating the Frequency Spectrum Characteristic of Stress Wave under Multistage Loading Stress

The stability of rock mass is destroyed by natural or human activities and leads to stress redistribution, causing the rock mass in a certain stressful environment. This study conducted a small disturbance impact tests on sandstone bar under loading stress by modified split Hopkinson pressure bar (SHPB). The results show that the reflection and transmission characteristics of stress wave are affected due to the loading stress changes in the sandstone porosity. The loading stress has a specific effect on the frequency spectrum distribution of the stress wave. The frequency spectrum curve has gone through the three stages, a gradual increase, then rapid attenuation, and finally a smooth development with the frequency increasing, and its dominant frequencies are mainly concentrated in 0∼2 kHz. The loading stress has a significant influence on the variation tendency of the dominant frequency. The dominant frequency experiences a slow increase and then tends to be stable, and the total energy of the frequency band shows a fast attenuation and then a gentle development, and its stress boundary point is σ/σc = 30%. The total energy attenuates as a first‐order exponential function and its attenuation rate shows an exponential‐linear function with the increasing loading stress, the farther away from the shock end, the faster the total energy attenuation is. The sandstone can filter the high‐frequency wave and the low‐frequency wave can penetrate rock media better. The closer the distance to the impact source, the greater the total energy of the frequency band. The frequency band energy is mainly concentrated in 0∼36.62 kHz, the higher the frequency of the frequency band is, the smaller the energy ratio is. Therefore, those conclusions can provide a reference for the evolution analysis of the stress wave spectrum in an excavated rock mass.

A study on radiation shielding potentials of green and red clayey soils in Turkey reinforced with marble dust and waste tire

The increasing radiation applications in our daily life makes it essential to protect ourselves from the harms of radiation by using alternative, cheap and natural materials. The present study aimed to analyze the radiation shielding abilities of green and red clayey soils from Oltu/Erzurum in Turkey, reinforced with waste tires and marble dust. For the purpose to investigate the shielding features of the samples, radiation attenuation parameters were determined by using EpiXS software, which can calculate partial or total cross-sections, partial or total mass attenuation coefficients, electron densities, effective atomic numbers, and buildup factors for energy absorption and exposure between 1keV and 1GeV. We compared the obtained mass attenuation coefficients and total atomic cross-section values of the samples with those of a widely used shielding material, ordinary concrete, to make a meaningful evaluation about the shielding potentials of the samples. To validate obtained values by EpiXS, we also calculated the mass attenuation coefficients of the samples by XCOM code, and compatible results were obtained. Among all the studied clayey soil samples, green clay reinforced with marble dust and waste tire has the highest shielding capability. It can also be mentioned that reinforcement with marble dust and waste tire improves the shielding ability of the clayey soils.

CT evaluated sarcopenia signals: Shorter survival for small cell lung cancer patients.

Sarcopenia is an independent risk factor for morbidity and mortality in patients suffering from small cell lung cancer (SCLC), however, a universal indicator of sarcopenia usable in clinical practice is still missing. A novel indicator for describing the severity of cancer could be helpful in tailoring the anti-tumor therapy. The aim of this study was to evaluate the computed tomography (CT) scans of total muscle area and radiation attenuation in patients suffering from small cell lung cancer. We used staging CT scans performed at the time of diagnosis to measure total muscle area (TMA) and average psoas density (PD) at level of the 3rd lumbar vertebra. TMA and PD were statistically evaluated in association with overall survival and disease staging. We used Mann-Whitney test and Spearman´s correlation coefficient for statistical testing and p-value under 0.05 was considered statistically significant. Retrospectively we examined 47 patients suffering from SCLC (mean age 65.05+/-7.3 years, BMI 23.97+/-4.4 kg/m2, BSA 1.77+/-0.2 m2, 30-day mortality was 4.3 % with 10 months median survival). As sarcopenia was pointed TMA under 55 and 39 cm2/m2 for men and women respectively. The sarcopenic patients had significantly shorter median survival (7 vs. 11 months, p=0.05). We observed a significant relationship between survival and performance status (Spearman´s correlation, R=-0.39, p=0.05). The patients were divided into two groups according to the extensive (ED, n=34) or limited (LD, n=13) form of the disease. We observed significant difference in PD (42.49+/-6.1 vs. 47.67+/-4.5 HU, p=0.006) between ED vs. LD groups.

INFLUENCE OF DIFFERENT NATURAL FIBER-BASED COMPOSITES USE AS A FILLER FOR CRACKING IN NUCLEAR REACTOR BIOLOGICAL SHIELDS

The biological shield is very important in the nuclear power reactor, so it is necessary to study the effect of crack on it. This work aims to study fiber composites as a radiation shielding for various purposes associated with nuclear installations, as properly as a repairing mixture for developing cracks in the biological shields of a nuclear power reactor. In this study, the MCNP-5 model of a pressurized water reactor (PWR) was used. Four different fiber composites of natural fiber (FP) (ρ= (1.373 g/ m3), fiber with lead (FPPb) (ρ=2.756 g /cm3), cement fiber (CF) (ρ=2.095 g/ m3) and cement-fiber-magnetite (CFM) (ρ =2.858 g /cm3) were used as the filler materials for cracking in the biological shield. The total mass attenuation coefficients µm for the studied composites have been calculated by the Win X-Com program of gamma-ray at an energy range from 0.15 – 20 MeV. Neutron and gamma-ray fluxes and dose rates were calculated through different distances of the reactor shields for different fiber composites. Total dose rates through biological shield without cracking and after cracking have been calculated. Radiation Protection Efficiency (RPE %) for all samples at the outer surface of the biological shield was calculated. The results showed that by using fiber composites as a filler for cracking, the values of flux and dose rate for neutrons and gamma-rays have decreased. Also, FPPb is the best material for gamma-ray because it contains lead, which has a high atomic number. While CFM has the best material shield for neutron and gamma-ray in addition to magnetite and boron carbide the properties of CFM composite were improved. Max. value of RPE % for FPPb was (43.1%), then CFM (37.2%), Fp (30.2%) and CF (20.2%). From these results, it can be concluded that plastic fiber composites were the best materials that can be used as a filler in the biological shield of nuclear power reactors.

Tropospheric Attenuation in GeoSurf Satellite Constellations

In GeoSurf satellite constellations, any transmitter/receiver, wherever it is located, is linked to a satellite with zenith paths. We have studied the tropospheric attenuation predicted for some reference sites (Canberra, Holmdel, Pasadena, Robledo, and Spino d’Adda), which also set the meridian along which we have considered sites with latitudes ranging between 60° N and 60° S. At the annual probability of 1% of an average year, in the latitude between 30° N and 30° S, there are no significant differences between GEO slant paths and GeoSurf zenith paths. On the contrary, at 0.1% and 0.01% annual probabilities, large differences are found for latitudes greater than 30° N or 30° S. For comparing the tropospheric attenuation in GeoSurf paths with that expected in LEO highly variable slant paths, we have considered, as reference, a LEO satellite constellation orbiting in circular at 817 km. GeoSurf zenith paths “gain” several dBs compared to LEO slant paths. The more static total clear-sky attenuation (water vapor, oxygen, and clouds) in both GEO and LEO slant paths shows larger values than GeoSurf zenith paths. Both for rain and clear-sky attenuations, Northern and Southern Hemispheres show significant differences.

Structural characterization and gamma-ray attenuation properties of rice-like α-TeO2 crystalline microstructures (CMS) grown rapidly on free surface of tellurite-based glasses

In this study, we extensively analyzed the structural, physical and gamma-ray attenuation properties of α-TeO2 CMS, which has unexpectedly been observed as a part of Sm2O3 doped TeO2–B2O3–V2O5 glasses synthesis process. The shape of α-TeO2 CMS was obtained from SEM analyses. Moreover, EDX, XRD and Raman examinations were utilized for systematic characterization of α-TeO2 CMS. In addition to experimental physical and structural studies on α-TeO2 CMSs, gamma-ray attenuation properties were also determined and compared with Quartz and some novel glasses such as PNCKM5, C25, SCNZ7 along with some commercial glasses such as RS253, RS253G18, RS323G19, RS360, RS520 using FLUKA general-purpose Monte Carlo code. EDX results indicated that only Te and O elements were available in the α-TeO2 CMS. The finding showed that gamma-ray attenuation competencies of α-TeO2 CMS is higher than many novel and commercial glasses in addition to traditional concrete shields. It can be concluded that further comparison studies can be done between normal glass structure and α-TeO2 CMS (or similar) occurred glass structures in terms of better understanding the total gamma-ray attenuation and the effect of α-TeO2 CMS.

The Normal Lung Index From Quantitative Computed Tomography for the Evaluation of Obstructive and Restrictive Lung Disease.

Our objective was to evaluate whether the normal lung index (NLI) from quantitative computed tomography (QCT) analysis can be used to predict mortality as well as pulmonary function tests (PFTs) in patients with chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD). Normal subjects (n=20) and patients with COPD (n=172) and ILD (n=114) who underwent PFTs and chest CT were enrolled retrospectively in this study. QCT measures included the NLI, defined as the ratio of the lung with attenuation between -950 and -700 Hounsfield units (HU) over the total lung volume (-1024 to -250 HU, mL), high-attenuation area (-700 to -250 HU, %), emphysema index (>6% of pixels < -950 HU), skewness, kurtosis, and mean lung attenuation. Coefficients of correlation between QCT measurements and PFT results in all subjects were calculated. Univariate and multivariate survival analyses were performed to assess mortality prediction by disease. The Pearson correlation analysis showed that the NLI correlated moderately with the forced expiratory volume in 1 second in subjects with COPD (r=0.490, P<0.001) and the forced vital capacity in subjects with ILD (r=0.452, P<0.001). Multivariate analysis revealed that the NLI of <70% was a significant independent predictor of mortality in subjects with COPD (hazard ratio=3.14, P=0.034) and ILD (hazard ratio=2.72, P=0.005). QCT analysis, specifically the NLI, can also be used to predict mortality in individuals with COPD and ILD.

FSO performance analysis of a metro city in different atmospheric conditions

Abstract In this article, a free-space-optics (FSO) model for a metro city based on real-time visibility data under different weather conditions is presented. Here, the relation between atmospheric attenuation and visibility value and its impact on the FSO performance is carried out. Also, the hybrid-SIM modulation technique is applied for the bit error rate (BER) improvement of the system. Here, Bhubaneswar (the capital of Odisha, India) is considered for the above analysis. The total attenuation, BER, and link margin are calculated for the FSO performance evaluation of Bhubaneswar city and these are simulated using Matlab. The simulation results show that the proposed hybrid-SIM modulation technique achieves about 2.9 dB of SNR improvement than the existing BPSK-SIM technique. Also, from the link margin analysis, it is observed that the sunny day is the most suitable for FSO link transmission. These results can be helpful to decide the FSO parameters and the FSO setup can be designed for any city.

High density of tungsten gadolinium borate glasses for radiation shielding material: Effect of WO3 concentration

The aim of this work is to study the radiation shielding properties in the glass systems xWO3: (70-x)Gd2O3: 30B2O3 (WGB) where x = 40, 45, 50, 55, and 60 mol%. These glasses were prepared by the melt quenching techniques. The Compton scattering technique was used to measure the experimental values of the total mass attenuation coefficient (MAC), the effective atomic number (Zeff), and the electron density (Neff) at 0.223 MeV–0.662 MeV. The measured MAC, Zeff, and Neff results were compared with the simulated and theoretical values obtained from Geant4 code and WinXcom software respectively. The comparison between the experimental, simulation and theoretical approaches for the determination of the several radiation shielding factors reflects the good detection system setup of Compton scattering experiment. The density is decreased with the increasing of WO3 concentrations from 6.1868 g/cm3 to 5.2669 g/cm3 and molar volume result demonstrated non-bridging oxygen and network former in the glass structure. The MAC, Zeff, and Neff results have similar trends, which increase by adding WO3 contents, and decrease with increasing of the energies. The HVL result showed that increased at the higher WO3 concentrations. Moreover, the HVL at 40 mol % of the concentration showed the highest density, and demonstrated better efficiency when compared with some standard shielding materials.

Correlation between Laser-Ultrasound and Microstructural Properties of Laser Melting Deposited Ti6Al4V/B4C Composites

The presence of large microtextured clusters (MTC) composed of small α-phase crystallites with preferred crystallographic orientations in 3D printed near-α titanium alloys leads to poor mechanical and fatigue properties. It is therefore crucial to characterize the size of MTCs nondestructively. Ti6Al4V/B4C composite materials are manufactured using Laser Melting Deposition (LMD) technology by adding an amount of nano-sized B4C particles to the original Ti6Al4V powder. TiB and TiC reinforcements precipitating at grain boundaries stimulate the elongated α crystallites and coarse columnar MTCs to equiaxed transition, and microstructures composed of approximately equiaxed MTCs with different mean sizes of 11–50 μm are obtained. Theoretical models for scattering-induced attenuation and centroid frequency downshift of ultrasonic waves propagating in such a polycrystalline medium are presented. It is indicated that, the studied composite material has an extremely narrow crystallographic orientation distribution width, i.e., a strong degree of anisotropy in MTCs. Therefore, MTCs make a dominant contribution to the total scattering-induced attenuation and spectral centroid frequency downshift, while the contribution of fine α-phase crystallites is insignificant. Laser ultrasonic inspection is performed, and the correlation between laser-generated ultrasonic wave properties and microstructural properties of the Ti6Al4V/B4C composites is analyzed. Results have shown that the deviation between the experimentally measured ultrasonic velocity and the theoretical result determined by the Voigt-averaged velocity in each crystallite is no more than 2.23%, which is in good agreement with the degree of macroscopically anisotropy in the composite specimens. The ultrasonic velocity seems to be insensitive to the size of MTCs, while the spectral centroid frequency downshift is approximately linear to the mean size of MTCs with a goodness-of-fit (R2) up to 0.99. Actually, for a macroscopically untextured near-α titanium alloy with a relatively narrow crystallographic orientation distribution, the ultrasonic velocity is not correlated with the properties of MTCs, by contrast, the central frequency downshift is dominated by the size and morphology of MTCs, showing great potentials in grain size evaluation.

Neutron/gamma radiation shielding characteristics and physical properties of (97.3−x)Pb−xCd–2.7Ag alloys for nuclear radiation applications

In this work, the shielding performance of (97.3–x)Pb–xCd–2.7Ag (x = 10, 18, and 30) ternary alloys against neutrons and gamma rays has been investigated. The microstructure, thermal and mechanical properties of the ternary alloys were examined. The total mass attenuation coefficients, for prepared alloys were determined at 662, 1173, and 1332 keV photon energies using NaI (Tl) scintillation detector. The theoretical values of were calculated using WinXCom program depending on the mixture rule. The estimated values were compared with the measured values for all investigated alloys. Atomic cross-section, σ a, electronic cross-section, σ e, effective atomic number, Z eff , effective electron number, N eff , and GP fitting parameters (b, c, a, Xk, and d) were determined. The exposure buildup factor, EBF, have been also calculated. Fast neutron attenuation for the prepared samples have been investigated via the macroscopic effective removal cross-section () calculation. Also, thermal neutron attenuation has been evaluated via neutron scattering calculator. The results show that the alloys containing 10 and 30% Cd compromise between superior tensile strength and Young modulus, while the pasty range, heat of fusion and ductility decreased with increasing Cd content. Moreover, the prepared ternary alloys have a high attenuation ability for gamma rays as the standard Pb. The increase of Cd ratio also significantly enhances the thermal neutron attenuation by amazing way along with the increase in the attenuation rate of fast neutrons.