Relative Attenuation Research Articles

Methamphetamine-related working memory difficulties underpinned by reduced frontoparietal responses.

Working memory difficulties are common, debilitating, and may pose barriers to recovery for people who use methamphetamine. Yet, little is known regarding the neural dysfunctions accompanying these difficulties. Here, we acquired cross-sectional, functional magnetic resonance imaging while people with problematic methamphetamine-use experience (MA+, n =65) and people without methamphetamine-use experience (MA-, n =44) performed a parametric n-back task (0-back through 2-back). Performance on tasks administered outside of the scanner, together with n-back performance, afforded to determine a latent dimension of participants' working memory ability. Behavioural results indicated that MA+ participants exhibited lower scores on this dimension compared to MA- participants (d = -1.39, p < .001). Whole-brain imaging results also revealed that MA+ participants exhibited alterations in load-induced responses predominantly in frontoparietal and default-mode areas. Specifically, while the MA- group exhibited monotonic activation increases within frontoparietal areas and monotonic decreases within default-mode areas from 0-back to 2-back, MA+ participants showed a relative attenuation of these load-induced activation patterns (d = -1.55, p < .001). Moreover, increased activations in frontoparietal areas from 0- to 2-back were related to greater working memory ability among MA+ participants (r = .560, p = .004). No such effects were observed for default-mode areas. In sum, reductions in working memory ability were observed alongside load-induced dysfunctions in frontoparietal and default-mode areas for people with problematic methamphetamine-use experience. Among them, load-induced activations within frontoparietal areas were found to have a strong and specific relationship to individual differences in working memory ability, indicating a putative neural signature of the working memory difficulties associated with chronic methamphetamine use.

Active control of noise radiated from a long cylinder: Can the Nyquist limitation be broken?

In the present paper, we consider active control of noise propagating from a long cylinder. For that purpose control sources are distributed on the external surface of the cylinder. They provide a secondary sound field which enables them to compensate for the noise field propagating outside. To implement active noise control, we apply an approach based on the Calderón potentials that have the projection property. Numerical simulations to attenuate broadband noise with different numbers of control sources per wavelength are carried out. The effect of the cylinder on the Green's function and consequent noise attenuation is studied. There are two key findings in this paper. First, the results demonstrate that the level of relative noise attenuation remarkably increases along with the growth of the distance. Second, it is shown that even less than two control sources per wavelength can provide essential noise cancelation. At first glance, this result contradicts the well-known Nyquist-Shannon sampling theorem. A theoretical explanation of this result is provided.

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.

Relevance of quadrupolar sound diffraction on flow-induced noise from porous-coated cylinders

This paper elucidates the link between the near-wake development of a circular cylinder coated with a porous material in a low Mach-number flow and the related aerodynamic sound attenuation. It accomplishes this by formulating the cylinder flow-induced noise as a diffraction problem. The necessity for such an approach is driven by experimental evidence obtained through acoustic beamforming and particle-image-velocimetry measurements, which reveal that the dominant noise sources for a coated cylinder are not localised on the body surface but rather in the wake, specifically at the outbreak position of the shedding instability. The acoustic field at the vortex-shedding frequency can be hence modelled by considering a compact lateral quadrupole at this location and employing an exact Green’s function tailored to a cylindrical geometry. Because of the diffraction of the sound waves radiated by the quadrupolar source on the cylinder surface, the resulting far-field directivity pattern resembles that of a dipole. The study demonstrates that the porous coating has the two-fold effect of decreasing the strength of the point quadrupole in the wake and moving its origin further downstream, reducing, in turn, the efficiency of the sound scattering. Consequently, the diffracted part of the acoustic field, which dominates the far-field noise for a bare cylinder in accordance with classical theory, provides a contribution that is comparable to the direct part. The results eventually indicate that quadrupolar sources must be considered to accurately predict the noise radiated from a porous-coated cylinder, even at low Mach numbers.

Incorporating the effect of frequency-independent attenuation within the on-axis spatial impulse response of a circular piston

The spatial impulse response is important for numerical simulations of diagnostic ultrasound. The spatial impulse response, which describes transient diffraction due to an impulsive input, yields closed form analytical expressions for various transducer geometries when the medium is lossless. These analytical expressions are advantageous for simulations that repeatedly evaluate these expressions at hundreds of thousands of points. However, spatial impulse responses evaluated for lossy materials typically require additional numerical calculations that substantially increase the computation time. Thus, analytical or rapidly converging numerical expressions for the lossy spatial impulse response are expected to greatly enhance present simulation methods. This motivates the derivation of on-axis spatial impulse responses for a circular piston that model frequency-independent attenuation. Closed-form analytical expressions for the on-axis spatial impulse response are introduced for two closely related frequency-independent attenuation models. The results show that, as the attenuation constant increases, the peak amplitudes of these lossy on-axis spatial impulse responses decrease. The lossy on-axis impulse response also decreases slightly as time increases beyond the initial arrival time, whereas the lossless on-axis spatial impulse response for a circular piston maintains a constant value after the initial arrival time.

Overview of modern technologies for measuring, predicting and correcting turbulent distortions in optical waves

This work is an analytical review of the components of modern technology for creating adaptive optics systems for correcting the distortion of optical waves propagating in a turbulent atmosphere. The work consists of the following parts: description of a technique for measuring fluctuations of optical waves in an atmospheric path, theoretical calculations of fluctuations by analytical analysis and mathematical modeling methods, technology for predicting turbulent air movement by the numerical solution of the Navier–Stokes equations and, finally, constructing adaptive optics systems that compensate for the turbulent distortions in optoelectronic image construction systems. Attention is focused on the peculiarities of fluctuations of specially created Laguerre–Gaussian and Bessel–Gaussian beams. Features of the propagation of vortex Laguerre–Gaussian and vortex Bessel–Gaussian beams for the transfer of orbital angular momentum through a turbulent medium are shown. Effects of the relative attenuation of phase and intensity fluctuations of the vortex-free Bessel–Gaussian beams in comparison with similar characteristics of the Gaussian beams are found. The integral scale of the coherence degree of the vortex Bessel–Gaussian beams and vortex conic waves is revealed to be highly sensitive to the influence of atmospheric turbulence, in contrast to the coherence radius of these beams and waves. Arguments are given in favor of the feasibility of constructing adaptive optical systems for a wide-aperture solar telescope operating under a strong atmospheric turbulence.

Prediction of proton stopping power ratios using dual-energy CT basis material decomposition.

Proton radiotherapy treatment plans are currently restricted by the range uncertainties originating from the stopping power ratio (SPR) prediction based on single-energy computed tomography (SECT). Various studies have shown that multi-energy CT (MECT) can reduce the range uncertainties due to medical implant materials and age-related variations in tissue composition. None of these has directly applied the basis material density (MD) images produced by projection-based MECT systems for SPR prediction. To present and evaluate a novel proton SPR prediction method based on MD images from dual-energy CT (DECT), which could reduce the range uncertainties currently associated with proton radiotherapy. A theoretical basis material decomposition into water and iodine material densities was performed for various pediatric and adult human reference tissues, as well as other non-tissue materials, by minimizing the root-mean-square relative attenuation error in the energy interval from 40 to 140keV. A model (here called MD-SPR) mapping predicted MDs to theoretically calculated reference SPRs was created with locally weighted scatterplot smoothing (LOWESS) data-fitting. The goodness of fit of the MD-SPR model was evaluated for the included reference tissues. MD images of two electron density phantoms, combined to form a head- and an abdomen-sized phantom setup, were acquired with a clinical projection-based fast-kV switching DECT scanner. The MD images were compared to the theoretically predicted MDs of the tissue surrogates and other non-tissue materials in the phantoms, as well as used for input to the MD-SPR model for generation of SPR images. The SPR images were subsequently compared to theoretical reference SPRs of the materials in the phantoms, as well as to SPR images from a commercial algorithm (DirectSPR, Siemens Healthineers, Forchheim, Germany) using image-based consecutive scan DECT for the same phantom setups. The predicted SPRs of the tissue surrogates were similar for MD-SPR and DirectSPR, where the adipose and bone tissue surrogates were within 1% difference to the reference SPRs, while other non-adipose soft tissue surrogates (breast, brain, liver, muscle) were all underestimated by between -0.7% and -1.8%. The SPRs of the non-tissue materials (polymethyl methacrylate (PMMA), polyether ether ketone (PEEK), graphite and Teflon) were within 2.8% for MD-SPR images, compared to 6.8% for DirectSPR. The MD-SPR model performed similar compared to other published methods for the human reference tissues. The SPR prediction for tissue surrogates was similar to DirectSPR and showed potential to improve SPR prediction for non-tissue materials.

Automated detection of early signs of irreversible ischemic change on CTA source images in patients with large vessel occlusion.

To create and validate an automated pipeline for detection of early signs of irreversible ischemic change from admission CTA in patients with large vessel occlusion (LVO) stroke. We retrospectively included 368 patients for training and 143 for external validation. All patients had anterior circulation LVO stroke, endovascular therapy with successful reperfusion, and follow-up diffusion-weighted imaging (DWI). We devised a pipeline to automatically segment Alberta Stroke Program Early CT Score (ASPECTS) regions and extracted their relative Hounsfield unit (rHU) values. We determined the optimal rHU cut points for prediction of final infarction in each ASPECT region, performed 10-fold cross-validation in the training set, and measured the performance via external validation in patients from another institute. We compared the model with an expert neuroradiologist for prediction of final infarct volume and poor functional outcome. We achieved a mean area under the receiver operating characteristic curve (AUC), accuracy, sensitivity, and specificity of 0.69±0.13, 0.69±0.09, 0.61±0.23, and 0.72±0.11 across all regions and folds in cross-validation. In the external validation cohort, we achieved a median [interquartile] AUC, accuracy, sensitivity, and specificity of 0.71 [0.68-0.72], 0.70 [0.68-0.73], 0.55 [0.50-0.63], and 0.74 [0.73-0.77], respectively. The rHU-based ASPECTS showed significant correlation with DWI-based ASPECTS (rS = 0.39, p<0.001) and final infarct volume (rS = -0.36, p<0.001). The AUC for predicting poor functional outcome was 0.66 (95%CI: 0.57-0.75). The predictive capabilities of rHU-based ASPECTS were not significantly different from the neuroradiologist's visual ASPECTS for either final infarct volume or functional outcome. Our study demonstrates the feasibility of an automated pipeline and predictive model based on relative HU attenuation of ASPECTS regions on baseline CTA and its non-inferior performance in predicting final infarction on post-stroke DWI compared to an expert human reader.

Research on the suppression method of sensor impact vibration parasitic effects in surface reflection pressure measurement.

Ground reflection pressure plays a crucial role in evaluating the destructive power of ammunition explosions. Accurately measuring this pressure is essential for assessing ammunition's destructive capability and guiding ammunition design. In this study, a theoretical analysis of the parasitic effect of shock and vibration was conducted and COMSOL was employed for performing a multi-physics finite element numerical simulation analysis to elucidate the attenuation characteristics of stress waves in commonly used shock- and vibration-resistant materials. Furthermore, a device was designed using aluminum foam and polytetrafluoroethylene to mitigate the parasitic effects on the ground reflection pressure sensor. Experimental testing was conducted to validate the device's effectiveness. The results demonstrated that the device successfully reduced the intensity of stress waves reaching the ground reflection pressure sensor, with a relative attenuation rate of 29.6% in peak stress values. The sensor measurements obtained with the suppression device exhibited smoother curves and higher signal-to-noise ratios, significantly improving the reliability of the measurement results. Our study holds considerable engineering application value in enhancing the accuracy of shock wave pressure measurements in explosive fields.

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.

Slowdown of group velocity of light in dual 1480 nm hybrid pump cascade structure of Er3+-doped optical fiber at room temperature

In this paper, a general theory of slow light transmission in dual 1480nm hybrid pump cascade structure of Er3+-doped optical fiber at room temperature is presented. Our objective is to compare the dual 1480nm hybrid pump cascade structure with the 1480nm and 980nm hybrid pump cascade structure in relative modulation attenuation, time delay, fractional delay, group velocity, refractive index, and signal optical loss. Through theoretical calculation, the maximum time delay is increased by 1.111 times and 1.162 times, and the maximum fractional delay is increased by 1.091 times and 1.132 times when the pump power ratio M=0.5 and 0.75. The loss coefficient is reduced to 0.1 when M=1. The results show that compared with the previous research methods, the dual 1480nm hybrid pump cascade structure can obtain larger time delay, fractional delay and smaller loss, which may have important applications for the optimization of optical communication systems.

Mapping Dust Attenuation and the 2175 Å Bump at Kiloparsec Scales in Nearby Galaxies

We develop a novel approach to measure the dust attenuation properties of galaxies, including the dust opacity, the shape of the attenuation curve, and the strength of the 2175 Å absorption feature. From an observed spectrum, the method uses a model-independent approach to derive a relative attenuation curve with an absolute amplitude calibrated using NIR photometry. The dust-corrected spectrum is fitted with stellar population models to derive the dust-free model spectrum, which is compared with the observed SED/spectrum from NUV to NIR to determine the dust attenuation properties. We apply this method to investigate dust attenuation on kiloparsec scales using a sample of 134 galaxies with integral field spectroscopy from MaNGA, NIR imaging from 2MASS, and NUV imaging from Swift/UVOT. We find that the attenuation curve slope and the 2175 Å bump in both the optical and NUV span a wide range at kiloparsec scales. The slope is shallower at higher optical opacity, regardless of the specific star formation rate (sSFR), the minor-to-major axis ratio (b/a) of the galaxies, and the location of spaxels within individual galaxies. The 2175 Å bump presents a strong negative correlation with the sSFR, while the correlations with the optical opacity, b/a, and the locations within individual galaxies are all weak. All of these trends appear to be independent of the stellar mass of the galaxies. Our results support the scenario that the variation of the 2175 Å bump is driven predominantly by processes related to star formation, such as the destruction of small dust grains by UV radiation in star-forming regions.

Role of Fractionation in Local Control of Spinal Metastases Treated with Stereotactic Radiosurgery

Optimal fractionation of spinal stereotactic radiosurgery (SRS) for spine metastases remains unknown. Retrospective data suggest decreased local failure (LF) with fractionated SRS of brain metastases. We evaluated our institutional outcomes of spinal SRS with the hypothesis that fractionation improves the rate of local failure compared to single-fraction treatment. This IRB-approved, retrospective analysis included patients with spine metastases treated with spinal SRS between October 2002 and November 2014 with evaluable follow-up imaging and no prior irradiation to the given segment. The exposure of interest was single- or multi-fraction SRS with a primary endpoint of the cumulative incidence of LF with death as a competing risk. We assessed bivariate associations between fractionation and single-fraction equivalent dose (SFED in Gy10) as well as high-risk features, defined as epidural extension (Bilsky Scale), paraspinous extension, and gastrointestinal (GI) vs non-GI primary. We calculated the rates of LF and vertebral body compression fracture (VCF) at 1-year, and assessed LF by fractionation when limited only to courses receiving SFED>18 Gy. We analyzed the association between fractionation and LF using subdistribution hazard ratios (SHR) estimated from competing risks regression with death as a competing risk and adjusting for lesion-specific characteristics as well as SFED to determine contribution of these variables to the estimated effect of fraction number on LF. We calculated relative attenuation for the contribution of SFED to this association, defined as [SHRfractions-SHRfractions+SFED] ÷ [SHRSFED-1]. In 293 patients with 516 spinal segments, lesions treated with single fraction compared to multi-fraction SRS had less epidural (19% vs 36%, p<0.001) and paraspinous (20% vs 35%, p<0.001) extension, more GI histology (17% vs 10%, p = 0.039), received a higher mean SFED (18.3 Gy vs. 16.6 Gy, p<0.001), and had a lower 1-year LF (8% vs 14%, p = 0.02), with no difference in VCF (7% vs. 5%, p = 0.38). After adjusting for high-risk features, single fraction SRS was associated with lower LF (SHR = 0.45, 95% CI 0.24-0.84, p = 0.02). After adjustment for SFED, this association of fractionation was attenuated by 53% and became insignificant (SHR = 0.78, 95% CI 0.44-1.37, p = 0.38). Overall, 1-year LF for SFED>18 Gy was 6% compared to 15% for <18 Gy (p<0.001). When limited to courses with SFED>18 Gy (n = 261), single fraction SRS had no improvement in 1-year LF compared to multi-fraction (6.6% vs 4.6%, p = 0.77). Single fraction SRS was associated with better local control compared to multi-fraction; however, much of this association was attenuated by SFED but not by high-risk features of treated lesions. To clarify the role of fractionation, we have initiated a prospective, randomized trial of single vs. multi-fraction SRS utilizing the same SFED.

A review of link budget analysis of satellite communication systems

At present, the link budget of satellite systems has become an essential part of the engineering design of satellite communication systems. Through the link budget, the performance of communication equipment and the loss of signal attenuation and interference during transmission can be comprehensively analysed, and the equipment resource configuration and device parameters can be continuously optimised to meet the user's communication capacity and quality requirements while leaving appropriate margins. This study aims to explore the link budget of the satellite system, study the parameters, channel characteristics and application of the satellite link budget, and provide a theoretical basis and practical reference for the design and performance optimisation of the satellite communication system. Firstly, the research background and significance of satellite communication links are introduced, and the characteristics and advantages of other communication systems are analysed and compared from multiple dimensions. The main factors affecting the link budget, such as path loss, related atmospheric attenuation, and carrier-to-noise ratio, were mainly discussed using the parameter estimation method and comparative analysis. Then, from the perspective of channel characteristics, the critical issues of satellite link budget, including signal-to-noise ratio, code rate and other factors, are discussed. Based on the above research, this paper summarises the performance evaluation of satellite communication systems and provides a reference for practical applications.

Tracing the attenuation of fipronil and its transformation products from a rice paddy field to receiving rivers using polar organic chemical integrative samplers

Irrational use of fipronil for rice pest control often occurred, resulting in high concentrations of fipronil and its transformation products (TPs) (collectively termed fiproles) in aquatic sediment, calling for a better understanding of the migration and transformation of fipronil in surface water as well as efficient methods for source identification. Herein, the fate and transport of fiproles from a paddy field to receiving rivers were assessed in Poyang Lake basin, Jiangxi, China using polar organic chemical integrative samplers with mixed-mode adsorbents (POCIS-MMA). Average concentrations of fiproles in water were 6.16 ± 6.32 ng/L, with median, minimum, and maximum values being 2.99 ± 0.67, 0.40 ± 0.08, and 18.6 ± 3.1 ng/L, respectively. In all samples, over half of fiproles (55.9 %–90.8 %) presented in the form of TPs and fipronil desulfinyl was the dominant TP. Two approaches were applied for source identification, including the change of molar concentration ratios of fipronil to its TPs and the relative attenuation values of fiproles normalized to a reference compound (acetamiprid) that was stable in aquatic environment. While the paddy field upstream was the main source of waterborne fiproles, additional input sources in the downstream region were identified. The present study indicated that the combination of attenuation of molar concentration ratios of micro-pollutants to their respective TPs and relative attenuation values of micro-pollutants' concentrations normalized to a reference compound measured by POCIS is an effective means to study the migration and transformation of micro-pollutants in field.

Three-dimensional femtosecond laser inscription of type a-based high-efficiency first-order waveguide Bragg gratings

A novel type of waveguide Bragg grating (WBG) is demonstrated based on femtosecond laser-induced Type A refractive index modifications, namely based of the photochemistry of silver species in a specialty ortho-phosphate glass matrix. First-order WBGs are reported in the near-infrared and down to 736 nm in the visible. Relative transmission measurements with a 500 µm long WBGs lead to narrow-bandwidth attenuations (sub-nm spectral FWHM) from 2.29 dB to 6.25 dB for periods from 240 nm to 280 nm, respectively. The corresponding estimated backward coupling coefficients show high values from 1.66 mm-1 up to 2.69 mm-1. Additionally, we report on a true 3D helix-shaped WBG that shows an even stronger relative attenuation of 10.3 dB for a 500 µm long WBG, equivalently corresponding to a backward coupling coefficient of 3.7 mm-1. These novel results pave the way for new silver-based laser-inscribed integrated photonic devices, among which the combination of Bragg gratings to form active/passive optical resonators, but also the direct inscription of WBG at the glass interface for enhanced sensing applications.

Attenuation of trace organic compounds along hyporheic flow paths in a lowland sandbed stream

Knowledge of flow paths in hyporheic zones of streams is essential for understanding different turnover processes of various chemicals, such as trace organic compounds (TrOCs). Due to the spatial heterogeneity of hyporheic zones, exact flow paths in situ are unknown and thus, pore water sampling along individual flow paths remains a major challenge. To this end, we developed and tested a novel method to enforce specific flow paths under field conditions. Therefore, U-shaped pipes of 40 cm total flow path length were installed in flow direction along a river cross section in the hyporheic zone of the urban lowland River Erpe (Germany). This allowed us to determine sediment properties and to collect pore water samples along the specific flow paths during 16 consecutive hours. The pore water was analyzed for electrical conductivity, redox parameters, and TrOCs. Diurnal electrical conductivity fluctuations in the surface water and their propagation to the end of the flow paths resulted in median residence times of 11.67 or 16.92 h for different specific flow paths. A clear redox zonation along the flow paths was found. Of the 18 TrOCs studied, five were strongly attenuated (i.e., relative attenuation to surface water > 75 %), three exhibited moderate attenuation (75 to 25 %), nine were only slightly or not attenuated (< 25 %), and one compound increased in concentration (relative formation > 25 %) along the entire flow paths. For TrOCs that showed strong or moderate attenuation, the attenuation occurred mainly within the first 5 to 15 cm. This work highlights (1) the importance of knowing the specific flow paths for a comprehensive understanding of TrOC turnover in the hyporheic zone and (2) the relevance of appropriate biogeochemical and hydrological conditions for the attenuation of TrOCs.

In situ measurement of relative attenuation length ofgadolinium-loaded liquid scintillator using source data at RENO experiment

We present in situ measurements of the relative attenuation length of the gadolinium-loadedliquid scintillator in the RENO (Reactor Experiment Neutrino Oscillation) detectorsusing radioactive source calibration data.We observed a steady decrease in the attenuation length of the Gd-LS in the RENO detectorsby ∼50% in about four years since the commissioning of the detectors.

NUMERICAL STUDY ON EFFECT OF PHASE ANGLE ON TORSIONAL AND LATERAL VIBRATIONS IN POWER TRANSMISSION SYSTEM EMPLOYING CARDAN SHAFT

A power transmission system driven by a Cardan shaft may experience severe vibration due to fluctuating rotational speed and moments transferred to the final drives, determined by the level of angular misalignment and phasing of the joint yokes. This study investigates the potential of an out-of-phase position displaced by a phase angle in attenuating vibrations. The governing equations representing the dynamics of the system are derived. The torsional and lateral vibration responses are numerically calculated over a range of input rotational speeds. When attenuating the vibration, the phase angle is set equal to the maximum twist that occurs during the in-phase position. Relative attenuation is used to investigate the phase angle effects. The effectiveness is studied for different levels of static angular misalignment. For the considered system, the results showed that for static angular misalignment greater than 20 degrees, the proposed phase angle arrangement could attenuate torsional vibration by more than 10 percent and significantly attenuate the lateral vibration.

Water content monitoring in water-in-oil emulsions using a delay line cell

The extraction process of crude oil requires addition of water, resulting in complex emulsions, in which the phases must be separated before the petrochemical processing starts. An ultrasonic cell may be used to determine in real time the water content in water-in-crude oil emulsions. The water content of emulsions can be related to parameters, such as propagation velocity, density and relative attenuation. The ultrasonic measurement cell developed here is composed of two piezoelectric transducers, two rexolite buffer rods, and a sample chamber. It is an inexpensive and robust system. The cell measures the parameters at different temperatures and flow conditions. The tests were performed using emulsions with water volume concentrations from 0% to 40%. The experimental results show that this cell is able to obtain more precise parameters, when compared to similar ultrasonic techniques. The data acquired in real time may be used to improve the emulsion separation, decreasing greenhouse gases and energy requirements.