Phase Angle Data Research Articles

Phase Behavior of Athabasca Bitumen

The phase behavior of Athabasca bitumen (Alberta, Canada) was determined from nanofiltered permeates and retentates with pentane-asphaltene mass fractions wA ranging from 0.053 to 0.57, and chemically separated Athabasca pentane maltenes and pentane asphaltenes based on differential scanning calorimetry and rheology measurements from (190 to 570) K at atmospheric pressure. Samples were subject to two sequential heating cycles. Composition, apparent heat-capacity, and phase-angle data were collected and interpreted jointly to define phase diagrams for nanofiltered maltene + nanofiltered asphaltene pseudobinary mixtures for each heating cycle. These pseudocomponents are shown to behave independently. During the first heating cycle, observed phase transitions for maltenes include: a broad low-temperature glass transition with a Tg from (215 to 230) K and a small first-order phase transition with a peak temperature Ttrs between (320 and 340) K linked to a fraction of Athabasca maltenes undergoing a crystal to...

Photometric modeling of Asteroid 5535 Annefrank from Stardust observations

In this paper the Stardust disk-integrated phase curve at phase 47.2–134.6° of the Asteroid 5535 Annefrank, combined with groundbased observations (at phase 2.3–18.3°), are fit with Hapke’s photometric model. We confirm Newburn et al.’s (Newburn, R.L. et al. [2003]. J. Geophys. Res. 108 (E11), 5117. doi: 10.1029/2003JE002106) observation that Annefrank exhibits a steep phase curve. This manifests itself in an unusually high fit surface roughness parameter of 49°. The single particle scattering albedo is 0.62, also high for an S-asteroid, while the fit phase function is more forward scattering than the typical S-asteroid being nearly isotropic with an asymmetry parameter of −0.09. The fit opposition surge width ( h = 0.015) is typical of S-asteroids. However these fits assume a spherical shape to the asteroid. Li et al. (Li, J., A’Hearn, M.F., McFadden, L.A. [2004]. Icarus, 415–431) have shown that this assumption may lead to significant errors particularly at high phase angles leading to higher modeled single particle scattering albedos, macroscopic roughnesses and more forward scattering phase functions than actually exhibited. Our results confirm this finding—fitting only the data below 90° phase yields lower particle albedos (0.41) and roughnesses (20°) and more backscattering particles (−0.19) than the fit including the high phase angle data. Overall Annefrank appears to be on the bright side but otherwise is typical for an S-type asteroid suggesting that it may be a recent collisional fragment with a relatively immature surface which has had relatively little time to be weathered.

Single-Phase Phase Angle Measurements in Electric Power Systems

Computation of phase angles using the discrete Fourier transform (DFT) algorithm has been proven to be sufficiently accurate in a variety of power system applications when the input signal is three-phase voltage and the voltage frequency is near the nominal value. However, the performance of the DFT algorithm in time of the singe-phase voltage input with a large frequency excursion so far has not been well explored, much less documented. This paper briefly discusses the importance of the synchronized phase angle measurement in power systems, and brings up the necessity of research on single-phase measurement systems. The performance of the DFT algorithm in power system phase angle measurements is thoroughly analyzed. Corresponding rectifying methods, including quasi-positive-sequence DFT and offset compensation, are proposed and examined by relevant numerical simulations and necessary laboratory tests. The results of the simulations and tests show a perfect match between the derived equations and the phase angle data, and thus verify the effectiveness of the proposed algorithm, which is believed to be able to greatly improve the performance of DFT in the aspect of phase angle calculation when severe power system upsets with remarkable frequency excursions are present.

Identifing Unique Conformational Forms of Phosphofructokinase Using Fluorescence Phasor Analysis

The two main parameters, phase angle and modulation, determined in frequency-domain fluorescence measurements, can be acquired with high precision. Unfortunately, when analyzing systems with complex decay mechanisms, error is often introduced by the imperfect modeling of this complexity. For questions that do not require a precise understanding of those mechanisms, the phasor approach allows a description of the system utilizing only the raw phase angle and modulation data with a corresponding improvement in reproducibility. In this investigation, we used phasor plots to describe the allosteric enzyme phosphofructokinase from E. coli (EcPFK). In our approach, we perform a direct transformation of the phase angle and modulation to the S and G function coordinates described in a Cartesian system as determined at an individual excitation modulation frequency. EcPFK contains a single tryptophan at position 311. Despite this simple composition, conventional fluorescence lifetime measurements of EcPFK exhibit complex decay behavior. The goal of this investigation is to describe the four species involved in the allosteric coupling between the substrate, fructose-6-phosphate (F6P) and the allosteric inhibitor, phosphoenolpyruvate (PEP), using the phasor approach. These four forms are: apo-EcPFK, EcPFK-F6P, PEP-EcPFK, and PEP-EcPFK-F6P). Special interest is on the ternary complex species (PEP-EcPFK-F6P) that is not considered in classic two-state models that attempt to explain the origin of allosteric behavior. The best results were obtained by exciting at 300 nm and collecting the fluorescence response at frequencies between 40 to 70 MHz. Our results show the presence of four unique conformations that correspond to the different ligated states of the enzyme. Notably, the ternary complex exhibits a unique phasor value, independent of whether it was formed by titrating the substrate followed by the inhibitor or vice versa. Supported by NIH Grant GM33216 and Welch Foundation Grant A1548.

Transfer function identification from phase response data

This paper introduces an improved procedure for the identification of a transfer function from phase angle data with prescribed frequency variation. It is shown how a transfer function can be identified from phase response data samples, by fitting a normalized function with constant magnitude using the vector fitting algorithm. The presented approach is numerically robust and leads to more accurate results than conventional approaches.

The asteroid lightcurve database

The compilation of a central database for asteroid lightcurve data, i.e., rotation rate and amplitude along with ancillary information such as diameter and albedo (known or estimated), taxonomic class, etc., has been important to statistical studies for several decades. Having such a compilation saves the researcher hours of effort combing through any number of journals, some obvious and some not, to check on prior research. Harris has been compiling such data in the Asteroid Lightcurve Database (LCDB) for more than 25 years with Warner and Pravec assisting the past several years. The main data included in the LCDB are lightcurve rotation periods and amplitudes, color indices, H–G parameters, diameters (actual or derived), basic binary asteroid parameters, and spin axis and shape models. As time permits we are reviewing existing entries to enter data not previously recorded (e.g., phase angle data). As of 2008 December, data for 3741 asteroids based on more than 10650 separate detail records derived from entries in various journals were included in the LCDB. Of those 3741 asteroids, approximately 3100 have data of sufficient quality for statistical analysis, including 7 that have “dual citizenship” – meaning that they have (or had) asteroid designations as well comet designations. Here we present a discussion of the nature of LCDB data, i.e., which values are actually measured and which are derived. For derived data, we give our justification for specific values. We also present some analysis based on the LCDB data, including new default albedo (pV) and phase slope parameter (G) values for the primary taxonomic classes and a review of the frequency–diameter distribution of all asteroids as well as some selected subsets. The most recent version of data used in this analysis is available for download from the Collaborative Asteroid Lightcurve Link (CALL) site at http://www.MinorPlanetObserver.com/astlc/default.htm. Other data sets, some only subsets of the full LCDB, are available in the Ephemeris of Minor Planets, The Planetary Data System, and the Minor Planet Center web site.

Interpretation of Complex Modulus Test Results for Asphalt-Aggregate Mixes

Abstract In this paper, a slightly different approach than usual is suggested to interpret complex modulus results for asphalt-aggregate mixes. Similar to current/common methods, the proposed analysis “forces” the test data to comply with thermo-rheological simplicity and linear viscoelastic (solid) behavior. However, unlike current methods, use is made of both dynamic modulus and phase angle data to obtain a master curve along with the corresponding time-temperature shifting. This is done by assuming a mathematical expression for the relaxation spectrum instead of an equation for the dynamic modulus master curve. Consequently, better compliance with linear viscoelastic theory is a-priori ensured for all subsequent analyses. Moreover, using the proposed method, conversion of the test results from the frequency domain to the time domain arises as a natural and simple outcome of the procedure which does not require sophisticated inversion techniques that are known to be computationally problematic. Complex modulus test results obtained for three different asphalt mixes are presented and analyzed in order to demonstrate the applicability of the proposed method.

High Frequency Length Mode PVDF Behavior over Temperature

AbstractIn an extension of earlier work, the temperature dependent parameters of PVDF operating in the length mode have been measured at frequencies useful in air ultrasound (20kHz to 100kHz) over a -45°C to +65°C temperature range. The length mode resonance of PVDF strips of different lengths was excited by mechanically clamping samples at the mid point during dielectric impedance testing conducted in a desiccated thermal chamber. Material properties were extracted from the impedance magnitude and phase angle data at temperature, and the various sample lengths allowed a range of resonant frequencies to be studied. Overall results generally confirm the visco-elastic behavior of PVDF. Testing was conducted on samples with both thin sputtered metal electrodes (∼60nm) and thicker elastomeric silver ink electrodes (∼8μm) to assess the performance difference. Silver ink is preferred in production as sputtered metal has current density an other limitations, but it causes a serious loss in performance at high frequencies.

Determination of Time-domain Viscoelastic Functions using Optimized Interconversion Techniques

ABSTRACT Several viscoelastic response functions are available to characterize the LVE behavior of asphalt concrete, some in time domain such as relaxation modulus E(t) and creep compliance D(t) and other such as complex modulus E* in frequency domain. The use of the complex modulus test has risen sharply after it has been incorporated in the M-E Pavement Design Guide and in the Superpave Simple Performance Test. With the availability of E* data it becomes advantageous to use mathematical interconversion techniques to obtain time-domain functions E(t) and D(t) which are typically used for constitutive modeling and other applications. This paper addresses the steps involved in conducting the interconversion between frequency-domain and time-domain functions. Issues considered include: a) presmoothing of raw data, b) refinement of phase angle data, c) Prony series representation of the fitted data including determination and sign-control of the Prony series coefficients, and d) interconversion techniques: approximate vs. exact. Finally, interconversion methods are evaluated by comparing D(t) data converted from E* to that measured in the lab.

First measurements with the Physikalisches Institut Radiometric Experiment (PHIRE)

We have constructed an experiment to perform bidirectional reflectance distribution function (BRDF) measurements of laboratory samples, and have used the experiment to characterize a sample of JSC-1 lunar regolith simulant. Characterizations relied on in-plane BRDF measurements in visible and near-infrared (NIR) bandpasses. The optical properties of the simulant sample were found to be similar to those observed for bright, lunar highland regions. Reflectance models (Hapke 1981. Bidirectional reflectance spectroscopy 1. Theory. J. Geophys. Res. 86(B4), 3,039−3,054; 1984. Bidirectional reflectance spectroscopy 3. Correction for macroscopic roughness. Icarus 59, 41−59; 1986. Bidirectional reflectance spectroscopy 4. The extinction coefficient and the opposition effect. Icarus 67, 264−280; 2002. Bidirectional reflectance spectroscopy 5. The coherent backscatter opposition effect and anisotropic scattering. Icarus 157, 523−534) made excellent fits to fixed incidence angle, variable emission angle data sets. However, the models were not found to extrapolate well to fixed, near-zero phase angle data at varying incidence angles, and no solutions were found that provided simultaneous, high quality fits to the two types of data sets. Except for the single-scattering albedo, the best-fit parameters of the fixed incidence angle data were statistically the same in the visible and NIR. Correlations between the reflectance model parameters were systematically examined, and strong correlations were found between single-scattering albedo and the two two-stream Henyey–Greenstein scattering parameters and, to a lesser extent, the small-scale mean surface roughness.

Characterization of Spectral Analysis of Surface Waves Shear Wave Velocity Measurement Uncertainty

The spectral analysis of surface waves (SASW) method is a nondestructive test for characterization of the variation with depth of the shear modulus of soils. While the testing procedure is well developed, only one preliminary study has investigated measurement uncertainty associated with SASW, and the methods utilized to quantify measurement uncertainty were prohibitive to routine assessment. Knowledge of this uncertainty, and ability to include its assessment in routine testing, would allow for inclusion of SASW results in reliability-based design and in assessment of the spatial variability of shear modulus. In this study, a large sample of test data was collected from two test sites. Characteristic statistics, statistical distribution, and measurement uncertainty were determined for each phase of SASW. Using the empirical statistical properties and measurement uncertainty results as validation criteria, an analytically based uncertainty assessment system was developed. Phase angle, inverse phase angle, and phase velocity data typically display a coefficient of variation (COV) of 2%, and the COV for combined phase velocity data is typically 1.5%. The COV for shear wave velocity is typically between 5 and 10%, and thus the inversion appears to magnify measurement uncertainty. Phase angle, inverse phase angle, phase velocity, and combined phase velocity data are normally distributed. Shear wave velocity samples at a given depth are generally normally distributed. Using a small sample of experimental data and the analytically based process developed in this study, the measurement uncertainty of SASW test results can be assessed as part of routine testing.

Wheat Sourdough Fermentation: Effects of Time and Acidification on Fundamental Rheological Properties

ABSTRACTThe fundamental rheological characteristics of a biologically acidified, a chemically acidified, and a neutral preferment (sourdough) were monitored over the course of a 24‐hr fermentation period using a split‐plot design. Three doughs were subsequently prepared in which 20% of the flour was in the form of the respective preferment. A control dough containing no fermented material was also prepared. The fundamental rheological properties of both the dough and its isolated wet gluten were determined. Laser‐scanning confocal microscopy was used to capture images of selected preferments and doughs. Results from the preferment showed that there was a decrease in elasticity (phase angle data from oscillatory measurements and relative recovery values from creep tests) and viscosity with fermentation time for all three preferments, all of which reached similar end values for these parameters. The microscopy images illustrated that the gluten strands were dissolved to a more amorphous structure during the fermentation period. Changes in the nature of the preferments were reflected in the rheological characteristics of the respective doughs and their wet glutens, which were significantly less elastic (phase angle and relative recovery data) and softer (maximum creep compliance) than the control treatment. It is concluded that degrading processes over time are key to the sourdough process.

Topography and phase imaging using the torsional resonance mode

The torsional resonance mode (TR mode) is an innovative technique recentlyintroduced for scanning probe microscopes (SPMs). In the TR mode, a cantilevertip vibrates laterally as compared to vibrating vertically in the tapping mode(TM). The tip in the TR mode remains at an almost constant height and interactsaggressively with the surface and/or the near surface because of very high torsionalstiffness. In this paper, a comparative study of TM and TR modes is presentedfor further understanding of the mechanism of the phase angle data producedduring the different tip–surface interaction modes. Topography and phase anglemeasurements were made on a self-assembled monolayer (SAM) sample with atwo-phase structure and metal particle (MP) tapes. It is found that althoughsurface topography images are similar using both techniques, the TR mode phaseangle image provides more detailed contrast than that obtained using the TMphase technique. The experimental evidence showed that viscoelastic deformationwas primarily responsible for the phase contrast and not the friction process.Next, statistical analysis of the phase angle on the MP tapes suggests that thetechnique can be used for evaluating the particle concentration and the uniformity ofviscoelasticity and thus screening of the magnetic tapes. The reasons for the improvedcontrast in the phase angle imaging in the TR mode are also discussed in this paper.

Analysis of Eddy Current Data Using a Probabilistic Neural Network (PNN)

To characterize flaws caused by intergranular attack (IGA) in steam generator tubes, the Babcock & Wilcox (B&W) Owners’ Group sponsored a program to study different techniques to determine the depth of flaws based on eddy current data obtained from Bobbin coil probes. Techniques based on multiple regression analysis, neural network regression, and artificial intelligence have been reported elsewhere. This report summarizes the results based on application of a probabilistic neural network (PNN) to classify the flaws into groups of different depths. As a starter, only two classes were selected: Class 1 contained flaws with actual maximum depths below 40% through-wall; Class 2 contained flaws with depths above 40% through-wall. Classification was based on the Bobbin coil peak voltage and the corresponding phase angle data at the three different excitation frequencies of 600, 400, and 200 kHz. The results were compared with results from destructive examination. The study showed that best results were obtained when only the peak voltages were used to train the neural network. Based on this approach, the network classified the flaws correctly 72% of the time. Two methods of improving the network performance are proposed.

AUTOREGRESSIVE ANALYSIS FOR THE DETECTION OF EARTHQUAKES WITH A RING LASER GYROSCOPE

The second-order autoregressive AR(2) model is used to analyze rotational data for seismic events captured by a large ring laser gyroscope. Both the Sagnac frequency and linewidth estimates obtained from this model sense the rotational components of seismic waves. An event of magnitude ML= 6.5 at a distance of D = 5.4° from a large ring laser gyroscope operating at its quantum limit is used to compare the AR(2) model with the previous analytical phase angle method of analysis. The frequency, linewidth and analytic phase angle data each satisfactorily estimate the rotation magnitude. The direct detection of rotational motion in the P wave coda is observed, demonstrating the conversion to transverse S wave polarizations by the local geology.

Determining Wheat Dough Mixing Characteristics from Power Consumption Profile of a Conventional Mixer

ABSTRACTA Hobart mixer with a pin‐type attachment was used to mix soft wheat flour dough. Power consumption profiles were measured continuously during mixing for 20 min using a current transducer and a data logging system. Experimental variables were quantity of flour (500, 1,000, and 1,500 g of dry wheat flour), water content (43, 45, and 47%, wb), and mixer speed setting (low, medium, and high). The power consumption profiles were evaluated by moving average and spectral analysis. Peaks in the power consumption profiles were located to determine the optimal mixing time. The optimal mixing times were then compared with storage and viscous moduli measured using a dynamic rheometer to assure the maximum strength of wheat dough at the optimal mixing time. Tolerance was determined using the signal amplitude and phase angle data from spectral analysis. Optimal mixing times of various doughs at medium speed ranged from 510 to 850 sec; low and high flour quantities required longer mixing times than medium quantity of flour. The optimal mixing time increased when the moisture content was lowered. Tolerance was affected by mixing speed and moisture content of flour

Signal processing algorithm for sound source localization with discretionarily distributed multiple receiving sensors

The deployment of strategically placed multiple receiving sensors has many practical ways to detect, localize, and classify a sound source in situations such as monitoring an isolated street disturbance in an urban environment with posted microphones or identifying a submerged object in the ocean with air-dropped sonobuoys. A simple processsing algorithm based on signals received from multiple sensors is derived from the information contained in the cross-spectrum matrix formed from the receiving sensors. Using the magnitude distribution of eigenvalues across the frequency bandwidth as the indication for the strength of signal excess in the frequency domain, their corresponding eigenvectors provide the required complex number weightings to select the related coherence components of the signal. By examining the phase angle data from each sensor’s weighting factor, a set of simultaneous algebra equations can be formulated to estimate the location of the sound source. The computation procedure of this approach is uncomplicated in comparison with the traditional triangulation method. Furthermore, the additional accompanied computed eigenvalues can be utilized for the characterization of the detected sound source, thereby establishing its identification reference. Simulated examples are used to test out the effectiveness of this multiple sensor sound source evaluation methodology at various operational scenarios.

Photometric properties of the Moon: Phase curves at small phase angles (0 – 10°) by clementine images

Using Clementine data, the phase curves of the lunar surface were investigated at small phase angles (0° to 10°) by direct comparison with standard phase angle (30°) data. We found the geological type dependence and wavelength dependence of the phase curve. Additionally, we found a negative correlation between the reflectance at standard phase angle 30° and the brightness ratio I( small phase angle) I(30°) . The dependencies on the terrain type and wavelength can be simply approximated by the dependence on the reflectance.

Supplementary Analysis of Io's Disk-Integrated Solar Phase Curve

Analysis of the disk-integrated phase curves of Io's leading and trailing hemispheres, as derived from combined groundbased and Voyager spacecraft measurements, shows that Io's leading side is more porous than its trailing hemisphere (assuming a globally uniform particle grain size distribution) and that the material of the trailing side is more opaque at 0.47 and 0.55 μm than the material of the leading hemisphere. The scattering nature of the leading hemisphere particles in the optically active layer of the regolith demonstrates both forward and backward scattering components. At 0.47 μm the forward scattering component is larger in amplitude than the backward scattering component, whereas at 0.55 μm they are nearly equivalent. No large phase angle data was available to adequately constrain the scattering behavior of the trailing hemisphere regolith. Measures of the geometric albedo are higher for the leading hemisphere than for the trailing hemisphere. Leading hemisphere geometric albedos are ∼0.7 to ∼0.85 at 0.47 and 0.55 μm, respectively. Trailing hemisphere albedos are ∼0.64 to ∼0.82 at 0.47 and 0.55 μm, respectively. Phase integral values for the leading hemisphere are 0.61 and 0.59 at 0.47 and 0.55 μm, respectively, which are lower than previously quoted values. Measures of the phase coefficient are higher than those previously published in the literature. No variations in Hapke parameter derived surface characteristics are observed between jovian and anti-jovian hemispheres.

Intrinsic dynamic viscosity obtained without phase angle data

Dilute-solution data on amplitude ratio and phase difference of stress and strain in sinusoidal shear testing are normally converted first to dynamic viscosity η′(c) and to η′′(c), where c is mass concentration of solute, and then extrapolated as c→0 to obtain the intrinsic values [η′] and [η′′]. The major source of error is usually measurement of phase angle, while amplitude ratio is more accurately determined. Here, it is shown that [η′] can be obtained from amplitude ratio alone, and also [η′′] from phase angle alone. Improved accuracy in obtaining [η′] is thereby possible with this new method of data analysis.