Relative Attenuation Coefficient Research Articles

Effect of High Temperatures on Mechanical and Shielding Properties of Lead–Zinc Tailings Concrete for Radiation Protection

Due to the high prices, the popularity of radiation shielding concrete (RSC) has been greatly limited. To solve this, this research reused the lead–zinc tailings (LZT) as a fine aggregate replacement ranging from 0% to 60% for the RSC. The results revealed that the RSC containing 30% LZT presented better workability and achieved 95.84% of the compressive strength and 98.49% of the linear attenuation coefficient of the RSC, and reached the highest splitting tensile strength values, which increased by 4.43%. Meanwhile, after the heat treatments, there were favorable correlations between the relative velocity and relative strength, as well as between the damage index and the relative linear attenuation coefficient, which could accurately reflect the degradation of not only the mechanical but also the shielding properties. Considering the temperature and shielding thickness, the reuse of LZT can bring considerable economic and environmental benefits.

Determination of dielectric properties of plaster blocks for sealing masonry using non-destructive frequency scanning methods

With the increasing use of traditional and new models of wireless communication systems, the study and determination of the electrical characteristics of materials used in civil construction is an important topic to establish an understanding of how the radio frequency signal behaves inside built environments. This study presents an extensive process of characterization of electrical parameters of plaster blocks used in the construction of walls. Different from the literature where a prior estimation of the data occurs to enable sampling parameters to be obtained, this work proposes an innovative way of obtaining them entirely based on the analysis of the material through frequency measurements, which results in a greater level of precision of the data results. Analyses are made in the frequency range from 0.7 to 5.2 GHz, which has been used for several wireless communication standards. To carry out the electrical characterization of dielectric materials, a non-invasive methodology is proposed based on an innovative combination of the Nicolson–Ross–Weir Method (NRW) and the Ray Tracing Method. Through the proposed methodology and an extensive campaign of measurements using frequency scanning equipment, calculated and experimental data of Shielding Effectiveness (SE), complex relative electrical permittivity, loss tangent, attenuation coefficient and conductivity were obtained for a wide range of frequency, considering different samples of plaster blocks. The obtained results are compared to those available in the related literature, confirming the accuracy of the proposed analysis.

Simultaneous imaging of ultrasonic relative backscatter and attenuation coefficients for quantitative liver steatosis assessment

Prevalence of liver disease is continuously increasing and nonalcoholic fatty liver disease (NAFLD) is the most common etiology. We present an approach to detect the progression of liver steatosis based on quantitative ultrasound (QUS) imaging. This study was performed on a group of 55 rats that were subjected to a control or methionine and choline deficient (MCD) diet known to induce NAFLD. Ultrasound (US) measurements were performed at 2 and 6 weeks. Thereafter, animals were humanely euthanized and livers excised for histological analysis. Relative backscatter and attenuation coefficients were simultaneously estimated from the US data and envelope signal-to-noise ratio was calculated to train a regression model for: (1) fat fraction percentage estimation and (2) performing classification according to Brunt’s criteria in grades (0 <5%; 1, 5–33%; 2, >33–66%; 3, >66%) of liver steatosis. The trained regression model achieved an R^2 of 0.97 (p-value < 0.01) and a RMSE of 3.64. Moreover, the classification task reached an accuracy of 94.55%. Our results suggest that in vivo QUS is a promising noninvasive imaging modality for the early assessment of NAFLD.

Application of electromagnetic disturbance technology in predicting ventriculoperitoneal shunt dependency after aneurysm-associated subarachnoid hemorrhage.

The aim of this study was to evaluate the predictive power of electromagnetic disturbance technology in patients with hydrocephalus after subarachnoid hemorrhage. This prospective, observational cohort study was conducted at The First Affiliated Hospital of Zhengzhou University and Nanfang Hospital. A total of 155 patients with subarachnoid hemorrhage (SAH) were enrolled in this study. Disturbance coefficients were recorded using a continuous sinusoidal signal in real time after SAH. The patients were divided into two groups: hydrocephalus group (patients who underwent shunt insertion within a month after SAH) and non-hydrocephalus group (patients without need for a ventriculoperitoneal shunt). We used SPSS to draw a ROC Curve to assess the ability of disturbance coefficients to predict the probability of hydrocephalus. Hydrocephalus occurred in 37 patients after SAH. The average disturbance coefficient of patients with hydrocephalus decreased by 25.14±9.78, and the disturbance coefficient of patients with no hydrocephalus decreased by 6.58±10.10 (one aspect of the present invention is a system of non-invasively monitoring hydrocephalus, cerebral edema, and intracranial bleeding comprising of a source emitting electromagnetic waves to brain tissue, a detector detecting said wave that propagates through said tissue, a signal conditioning unit amplifying and filtering said wave, a quadrature detector estimating magnitude and phases of said wave, and a parameter estimator calculating the complex wave number, relative attenuation coefficient (RAC), relative phase shift (RPS), wave speed change (WSC), and travel-time difference (TTD) of said brain, and assessing status of hydrocephalus and cerebral edema). The difference was statistically significant (t=9.825, P<0.001). The decrease in disturbance coefficient can be used to predict the occurrence of hydrocephalus, and if the disturbance coefficient decreases by more than 15.5 (sensitivity, 92.37%; specificity, 86.49%), it can be used to indicate the occurrence of hydrocephalus. The disturbance coefficient can predict the occurrence of hydrocephalus. The greater decline of the disturbance coefficient, the greater probability of occurrence of intracranial hydrocephalus. Hydrocephalus can be early detected. However, the CT scan is necessary to confirm the occurrence of hydrocephalus. Early diagnosis and early treatment may improve the prognosis of patients with hydrocephalus after subarachnoid hemorrhage.

Intelligent calculation method of relative sonic attenuation and its application to fracture evaluation in tight sandstone reservoir

Fractured tight reservoirs have widespread exploration and development prospects. For these types of reservoirs, fractures provide pathways for fluid flow and storage spaces for tight oil and gas, which play a significant role in increasing production. In order to explore a fine fracture evaluation scheme for tight reservoirs, we firstly proposed an intelligent calculation method for the relative sonic attenuation; and then developed a novel semi-quantitative evaluation approach for the equivalent fracture width based on relative sonic attenuation and physical experimental results of the effect of fracture on sonic attenuation. The acoustic experimental results of the models with fractures show that the S-wave relative attenuation coefficients have a good correlation with the fracture attribute parameters. This lays a foundation for the fine fracture evaluation based on attenuation information. Field application results of the intelligent calculation method for relative attenuation and the inversion method for fracture width have been validated by comparing them with results from image logging, S-wave anisotropy estimation, and production test data, which demonstrates the feasibility and correctness of the proposed methods. The investigation depth of the proposed fracture evaluation scheme based on acoustic attenuation is significantly larger than that of the image logging, which provides a new optional scheme for fine fracture evaluation, especially for effective fracture evaluation; and it makes up for the deficiencies of the image logging fracture evaluation method.

Field Test of Vibration Wave Attenuation Coefficient Model in Casing Medium

The casing string is a very good down-hole signal transmission channel due to its rigidity which means it can reduce attenuation in vibration wave propagation. Based on elastic mechanics theory, we obtain the wave equations of vibration propagating in the free casing, analyze the transmitting law of the vibration wave in the well fluid-casing-cement system and found that the attenuation of the vibration wave is mainly caused by the energy absorbed including the well fluid, the casing and the cement ring. Based on the attenuation factors which affect the wave propagation, we get the vibration wave attenuation coefficient model and calculate the relative attenuation coefficients in different casing strings. By detecting and analyzing the drilling plug signal in the second spud, the field test results prove the feasibility of long-distance transmission and the low attenuation of vibration wave in the casing string, and get the attenuation coefficient of casing size 9 5/8, which is similar to the simulation result.

Characterization of pitting resistance of metal materials with ultrasonic microscope

Pitting resistance of metal materials is usually evaluated by immersion experiments or electrochemical experiments, etc. However, these methods are destructive and easily affected by experimental conditions. In this paper, a method based on the ultrasonic relative attenuation coefficient of high-order cumulant (URA_HOC) is proposed to characterize the pitting resistance of metal materials. The new method can reduce the influence of Gaussian noise and is sensitive to microstructure changes, which enables the new method to evaluate the pitting resistance accurately. In order to verify the effectiveness of proposed method,duplex stainless steel 2205 with different compositions are detected by ultrasonic microscope and electrochemical experiment, respectively. The results shown that the prediction accuracy of URA_HOC on the pitting resistanceis up to 94%. Therefore, the new method canachieve non-destructive, high-efficient and large-scale measurement of pitting resistance.Besides, the new method also provides arapid characterization of the microstructure of materials.

Experimental research on the acoustic transmission characteristics of refractory materials

The damage acoustic emission (AE) signal of refractories can be used to evaluate the classification and degree of the phase damage, which is different from the traditional damage location study in AE. In the analysis of AE signal, considering the nonuniformity of refractory inner structure, results of damage source inspection are usually affected by the signal transmission path. Therefore, the influence of transmitting path should be studied first. Piezoceramic material, capable of actuation and sensing, is commonly used to build AE probes. In this paper, two kinds of industrial refractories were selected as research objects and AE probes were chosen to generate emission acoustic signals. The relative amplitude attenuation coefficient and the relative energy attenuation coefficient were consequently designed as discriminant indicators to study the propagation characteristics of stress wave under different transmission paths and thicknesses. Results indicate that energy attenuation is higher than amplitude attenuation. Meanwhile, signal attenuation is principally proportional to transmission distance without directional selectivity. The above conclusions provide strong support to arrange AE sensors for nondestructive testing in refractory industry.

Evaluation of Dosimetric Characterization of Homemade Bolus for Radiation Therapy

The bolus is also known a tissue compensation that has material similar to body tissue and placed directly onto the skin surface for radiation therapy. This study aims to characterize and evaluate the synthesized homemade bolus using Natural Rubber, Paraffin Candle, Play-Doh, and Paraffin Wax Pure for radiation therapy using a photon beam. Several dosimetry properties of the synthesized of the bolus, including relative electron density (RED), transmission factor, attenuation coefficient, and percentage of surface dose (PSD), were investigated. All the synthesized bolus made with the same dimension of 11×11 cm2 with the thickness is 1 cm. CT-Scan was used to measure relative electron density (RED) where as LINAC 2300iX with energies 6 and 10 MV were used to evaluate percentage of surface dose. The RED value of all bolus material is in accordance with the provisions of bolus as a tissue compensation of the human body, which is almost the same as the value of HU in breast organs, skin, fat and adult bones. Large transmission factors and attenuation coefficients of each bolus correspond to bolus from paraffin candles as the default bolus of the hospital. The maximum bolus dose value increases when compared to measurements without bolus.

Study of the influence of oscillatory processes in a mobile vehicle on the running smoothness characteristics

The issue of optimizing the dynamic characteristics of a mobile vehicle depending on the operating conditions is considered. The optimization problems were solved taking into account the random nature of dynamic loads. The task of transforming the input effect on the elements of the mobile machine was solved in a deterministic aspect using integrated criteria. As a measure of the accuracy of the introduced criteria, the standard deviation was used. The minimum values of vertical reactions on the header shoes were determined by the dispersion of its oscillations, taking into account the spectral density of the irregularities of the agricultural background. It was found that the frequency characteristics of the header shoes also depend on the vertical and longitudinal-angular vibrations of the combine separator. Optimality criteria are presented for assessing the dispersion of vibrational parameters of vehicles from external influences. The general optimization criterion was determined based on the independence of the objective functions and the maximum quantile of the normal distribution, which allowed, in a probabilistic aspect, to evaluate the optimization efficiency for agricultural machinery with a wide range of applications. The local optimum was determined by the expression of objective functions in terms of elementary functions, taking into account statistical parameters and the nature of the distribution of a random variable. The optimal transfer function was determined based on the minimum value of the standard deviation of the objective function taking into account the Fourier variables. The determination of the local optimum was carried out graphoanalytically by the objective function of smoothness and by the probabilistic criterion. The optimal value of the relative attenuation coefficient of vertical oscillations of the separator body was determined, the reason for its minimization and the probability of exceeding the permissible vibration level were established. A method for determining the transfer function to predict the smoothness of the combine is presented. The possibilities of the proposed optimization method are estimated.

Monte Carlo simulation of some gel dosimeters' behaviour in photonic radiation field: research on attenuation coefficient

In this study, a model of MCNP based on Monte Carlo method was developed to calculate the mass attenuation coefficients of 15 gel dosimeters, namely LMD1, LMD2, PAG, nPAG, nMAG, VIPAR, PABIG, MAGAT, MAGAS, PAGAT, PRESAGE, BANG-1, BANG-2, BANG-3 and MAGIC at 10–1332.5 keV photon energies. In order to validate the model, the obtained results of simulation work were compared with data of XCOM. It was observed that the results were in high accordance with data of XCOM program. Accordingly, the model can be used in dosimetry, medicine and industry for various polymers and materials. Furthermore, on one hand, parameters of radiation transport in developing new gel dosimeters and materials can be calculated and assessed using the proposed model before clinical application and on the other hand, the data obtained by simulation can be used to analyze the behavior of gel dosimeters in photon radiation fields. In this regard, among 15 gel dosimeters studied here, LMD1 and PRESAGE showed the best and worst performance in comparison with other gel dosimeters, respectively. Other gel dosimeters had a poor performance, especially in energy range of 10–50 keV. Their relative mass attenuation coefficient difference with the value of water was less than 1.4%.

Discrete switching of elastic elements as a way of ensuring damping in Duffing oscillator

With the aim of improving the efficiency of damping oscillations in non-autonomous Duffing system, the elastic element is divided into deformable and accumulating parts; between them four times a period discrete switching is enabled, which consists of the intermittent disconnection and connection parts. The concepts of the spasmodic changes in the initial length of the forged part and the displacement of the protected object static equilibrium state are introduced. Mass transfer between the parts of the elastic element, occurring at the moments of discrete switching, leads to dissipation of mechanical vibrations energy. Using the introduced concepts, characteristics of the positional forces are developed, their harmonic linearization is made, their equivalent stiffness damping and relative attenuation coefficients are found, the influence of amplitude of relative oscillations on them and the parts mass and initial tension ratio are analyzed.

Assessing surface characteristics of eroded dentine with optical coherence tomography: a preliminary in vitro validation study

We conducted the first pilot study to investigate the use of the attenuation coefficient from an optical coherence tomography (OCT) backscattered signal as a measure of surface roughness changes in eroded dentine at an early stage of the erosion process. Ten human premolar root samples were subjected to citric acid treatment before scanning by OCT. The extracted relative attenuation coefficient (μR) from backscattered OCT signals was shown to increase with the duration of acid challenge. Validated against roughness measurements (rSa) from scanning electron microscopy scans, μR is significantly correlated with rSa indicative of severity of erosion (p<0.01, r=0.9195). We conclude that the OCT attenuation coefficient of the immediate subsurface in eroded dentine is a potential surrogate measure for its surface roughness. However, further work should be performed to study how it relates to the surface and immediate subsurface changes effected by other mechanical wear before it could unequivocally be used as a surrogate measurement for surface roughness.

Relative Attenuation and Beam Softening Study with Flattening Filter Volume Reduction: Monte Carlo Study

The flattening filter (FF) volume reduction increases the clinical photons for deep tumor treatment. The beam softening determination is crucial for flattening filter improvement in geometry and materials. Determination and understanding the photon beam properties using material and geometry of a beam modifier is very important for dosimetry improvement in radiotherapy department and also for patient life quality development. This Monte Carlo study aims to investigate the relative attenuation and associated beam softening due to flattening filter volume reduction. The FF volume was reduced by 10, 20, and 30% of the initial volume data provided by the manufacturer. The relative attenuation and beam softening coefficients increased with FF volume reduction more near the beam central axis than the beam edge. We have illustrated that relative photon beam softening coefficient v was more stable than the coefficient u as a function of offaxis distance and with FF volume reduction. For increasing the photon fluence and dose delivered inside the phantom volume as mentioned in IAEA protocols, the FF volume should be reduced more near the FF top region than the FF edge region. Our work can be a basic investigation that will be used in improvement for the future linac configuration in terms of photon beam softening for material, geometry, and volume that were used in beam modifiers as a flattening filter.

Powder conglutination detection in polypropylene production pipelines using acoustic-ultrasonic technique

In the production of polypropylene, powder conglutination in pipelines easily leads to blockage, which can seriously affect the operation safety of the pipeline, so it is very important to detect and quantitatively evaluate the powder conglutination. This paper proposed an acoustic-ultrasonic (AU) quantitative evaluation method for powder conglutination detection in polypropylene production pipelines. A simulation model was developed to investigate the wave propagation characteristics of conglutinated layers with different areas and thicknesses using stress wave factors (SWF). Experiments were then conducted to develop a quantitative evaluation method for polypropylene powder conglutination. The results show that the relative attenuation coefficients of peak amplitude, peak-to-peak amplitude and the energy and the peak of the power spectrum all follow an approximate linear relation with the areas and thicknesses of the conglutinated layers. For either area or thickness evaluation, the energy or the peak of the power spectrum of AU signals has higher sensitivity than peak amplitude or peak-to-peak amplitude. Moreover, compared with conglutinated area evaluation, all the SWF models for thickness evaluation were more reliable, where the errors were all less than 7%. As a result, the AU technique is an effective means to detect powder conglutination in polypropylene production pipelines, and high sensitive and accurate quantitative evaluation is feasible with some of the stress wave factors of AU signals.

Integrated On-Chip THz Sensors for Fluidic Systems Fabricated Using Flexible Polyimide Films

We investigate the use of an on-chip terahertz (THz) frequency sensor formed on a flexible, thin-film polyimide substrate to measure the properties of liquids encapsulated in a glass-walled capillary. We observe changes in the attenuation and velocity of the time-domain THz signal, which allows extraction of the broadband THz refractive index and relative attenuation coefficients of the liquid. The technique is used for sensing members of a homologous series of primary alcohols, and the results compared with those obtained from a free-space terahertz frequency time-domain spectroscopy system.

Study of thermoviscous dissipation on axisymmetric wave propagating in a shear pipeline flow confined by rigid wall. Part II. Numerical study

Axisymmetric acoustic wave propagating in a shear pipeline flow confined by a rigid wall is studied in the two-part paper. The effects of viscous friction and thermal conduction on the acoustic wave propagating in the liquid and perfect gas are respectively analyzed under different configurations of acoustic frequency and shear mean flow. In Part 2 of this paper, comprehensive analysis of the effects of shear mean flow and acoustic frequency on the features (relative phase velocity and attenuation coefficient) of the acoustic wave are numerically addressed in cases of water and perfect gas respectively. Comparisons between the non-isentropic and isentropic models are provided in details. Meanwhile, discussions of the thermoviscous effects on the acoustic wave between water and perfect gas are given.

Using attenuation coefficients from optical coherence tomography as markers of vocal fold maturation.

Optical coherence tomography (OCT) is a promising technology to noninvasively assess vocal fold microanatomy. The goal of this study was to develop a methodology using OCT to identify quantifiable markers of vocal fold development. In vivo study. A two-step process was developed to reproducibly image the midmembranous vocal fold edge of 10 patients younger than 2 years and 10 patients between 11 and 16 years of age using OCT. An image analysis algorithm was implemented to extract OCT-derived A-lines for each patient. These A-lines were divided into three zones according to apparent changes in slope. Relative attenuation coefficients, or tissue- and system-dependent parameters that describe the rate at which optical signal decays, were calculated for each zone. Young patients had distinct relative attenuation coefficients in zone 1 (P < .0001), whereas zones 2 and 3 were indistinct (P = .1129). Older patients had distinct relative attenuation coefficients in zones 1, 2, and 3 (P < .0370). Between age groups, relative attenuation coefficients were different in zones 2 and 3 (P < .0001, P = .0315, respectively) and indistinct in zone 1 (P = .1438). Relative attenuation coefficients can be used as markers of vocal fold development. Differences in relative attenuation coefficients likely represent changes in extracellular matrix structure within the lamina propria and may become useful for guiding treatment of voice disorders in the pediatric population. NA Laryngoscope, 126:E218-E223, 2016.

Robust determination of mass attenuation coefficients of materials with unknown thickness and density

An alternative approach is used to measure normalized mass attenuation coefficients (µ/ρ) of materials with unknown thickness and density. The adopted procedure is based on the use of simultaneous emission of Kα and Kβ X-ray lines as well as gamma peaks from radioactive sources in transmission geometry. 109Cd and 60Co radioactive sources were used for the purpose of the investigation. It has been observed that using the simultaneous X- and/or gamma rays of different energy allows accurate determination of relative mass attenuation coefficients by eliminating the dependence of µ/ρ on thickness and density of the material.

Computation of thyroid doses and carcinogenic radiation risks to patients undergoing neck CT examinations

The aim of the study was to investigate how differences in patient anatomy and CT technical factors in neck CT impact on thyroid doses and the corresponding carcinogenic risks. The CTDIvol and dose-length product used in 11 consecutive neck CT studies, as well as data on automatic exposure control (AEC) tube current variation(s) from the image DICOM header, were recorded. For each CT image that included the thyroid, the mass equivalent water cylinder was estimated based on the patient cross-sectional area and average relative attenuation coefficient (Hounsfield unit, HU). Patient thyroid doses were estimated by accounting for radiation intensity at the location of the patient's thyroid, patient size and the scan length. Thyroid doses were used to estimate thyroid cancer risks as a function of patient demographics using risk factors in BEIR VII. The length of the thyroid glands ranged from 21 to 54 mm with an average length of 42 ± 12 mm. Water cylinder diameters corresponding to the central slice through the patient thyroid ranged from 18 to 32 cm with a mean of 25 ± 5 cm. The average CTDIvol (32-cm phantom) used to perform these scans was 26 ± 6 mGy, but the use of an AEC increased the tube current by an average of 44 % at the thyroid mid-point. Thyroid doses ranged from 29 to 80 mGy, with an average of 55 ± 19 mGy. A 20-y-old female receiving the highest thyroid dose of 80 mGy would have a thyroid cancer risk of nearly 0.1 %, but radiation risks decreased very rapidly with increasing patient age. The key factors that affect thyroid doses in neck CT examinations are the radiation intensity at the thyroid location and the size of the patient. The corresponding patient thyroid cancer risk is markedly influenced by patient sex and age.