Single-line Method Research Articles

Investigation on the triaxial creep characteristic of coarse granular materials with different initial void ratios

The creep deformation of coarse granular materials is closely related to the state of creep stress and the degree of compaction. A serious of triaxial creep tests using the single-line method were carried out to investigate the influence of initial void ratio and triaxial stress state on the creep deformation and creep strain direction of coarse granular materials. The test results primarily indicate that the creep strain increases with an increase in initial void ratio under identical stress conditions, and the volumetric creep strain decreases with an increase in stress ratio under high confining pressure conditions. Furthermore, the variation in the initial void ratio has little influence on the direction of creep strain under the same creep stress state. The effect of generalized stress on the final creep strain and creep dilation ratio were further discussed. It was observed that the final deviatoric creep strain exhibits a stronger correlation with the deviatoric stress q compared to the mean normal stress p. Additionally, the creep dilatancy decreases with an increase in stress magnitude under identical stress ratio conditions. Based on the test results, a computation model for the final deviatoric creep strain with the consideration of initial void ratio and creep stress was proposed by modifying a basic power function with deviatoric stress q as the variable. After that, a modified stress-dilatancy equation for coarse granular materials was used to predict the direction of strain during creep process. Finally, the final volumetric creep strain was indirectly calculated by integrated the computation model for the final deviatoric creep strain and the creep stress-dilatancy equation. The reasonable of the proposed model was verified through a comparison of computation results and test results.

Study on the wetting effect of the silty clay reservoir bank sub-grade

In this paper, the deformation characteristics of silty clay after immersion in water were studied. The wetting test of silty clay in a stratum in Chongqing under different confining pressures and different stress levels was carried out by using multi functional triaxial apparatus. Through the single line method and double line method experiments, the law of wetting deformation of silty clay was obtained and a new curve formula was fitted.

Screening for spontaneous preterm birth by cervical length and shear-wave elastography in the first trimester of pregnancy

First-trimester cervical length for the prediction of spontaneous preterm delivery remains controversial. A better method for the measurement of the first-trimester cervical length and additional cervical ultrasound parameters for the identification of women at high risk for spontaneous preterm delivery are needed. This study aimed to compare the predictive value of cervical length measured by 2 different methods in the first trimester of pregnancy to predict spontaneous preterm delivery and to explore the potential value of first-trimester cervical shear-wave elastography for the prediction of spontaneous preterm delivery. This was a prospective study in unselected singleton pregnancies at 11+0 to 13+6 weeks' gestation. Cervical length was measured by the following 2 methods in the base-cohort population: (1) a linear distance between the 2 ends of the glandular area around the endocervical canal (single-line method: cervical length-s) and (2) a sum of the linear distance from the internal os to the greatest cervical curvature and the linear distance from this point to the external os (2-line method: cervical length-t). In a substudy, cervical shear-wave elastography scores for 9 regions of interest (inner, middle, and external parts of anterior lip, endocervical canal, and posterior lip) in midsagittal plane were also obtained by transvaginal ultrasonography. The screening performance of the first-trimester cervical length measured by the 2 different methods for the prediction of spontaneous preterm delivery was assessed by receiver operating characteristics curve analysis. The areas under the curves were compared using a DeLong test. The predictive performance of a soft cervix (mean elastography scores with multiple of median <5th, 10th, 15th, 20th, and 25th percentile) for spontaneous preterm delivery was also determined. Among a total of 2316 included pregnancies, spontaneous delivery at <37 and <34 weeks' gestation occurred in 111 cases (4.8%) and 20 cases (0.9%), respectively. In the total study population, when compared with the term delivery group, the median cervical length-t was shorter in women with spontaneous delivery at <34 weeks' gestation (36.9 mm vs 35.1 mm; P=.015), but there was no clear correlation for cervical length-s. Receiver operating characteristics curves demonstrated that cervical length-t achieved better performance in predicting spontaneous delivery at <34 weeks' gestation (area under the curve, 0.658 vs 0.573; P<.01) than cervical length-s. The best combined model to predict spontaneous delivery at <34 weeks' gestation was provided by cervical length-t and history of preterm delivery (area under the curve, 0.692). In the substudy, a soft cervix with a mean elastography scores multiple of median <10th percentile had a relative risk of 7.8 (95% confidence interval, 2.1-28.6) for spontaneous delivery at <34 weeks' gestation; the detection rate was 44.4% at a false-positive rate of 9.0%. The 2-line approach provides a better estimate of the actual first-trimester cervical length and achieves better performance as a screening tool for spontaneous preterm delivery at <34 weeks' gestation than the conventional measurement. A soft cervix as determined by shear-wave elastograpthy in the first trimester is associated with an increased risk for subsequent spontaneous preterm delivery.

DMD-based hyperspectral microscopy with flexible multiline parallel scanning

As one of the most common hyperspectral microscopy (HSM) techniques, line-scanning HSM is currently utilized in many fields. However, its scanning efficiency is still considered to be inadequate since many biological and chemical processes occur too rapidly to be captured. Accordingly, in this work, a digital micromirror device (DMD) based on microelectromechanical systems (MEMS) is utilized to demonstrate a flexible multiline scanning HSM system. To the best of our knowledge, this is the first line-scanning HSM system in which the number of scanning lines N can be tuned by simply changing the DMD’s parallel scanning units according to diverse applications. This brilliant strategy of effortless adjustability relies only on on-chip scanning methods and totally exploits the benefits of parallelization, aiming to achieve nearly an N-time improvement in the detection efficiency and an N-time decrease in the scanning time and data volume compared with the single-line method under the same operating conditions. To validate this, we selected a few samples of different spectral wavebands to perform reflection imaging, transmission imaging, and fluorescence imaging with varying numbers of scanning lines. The results show the great potential of our DMD-based HSM system for the rapid development of cellular biology, material analysis, and so on. In addition, its on-chip scanning process eliminates the inherent microscopic architecture, making the whole system compact, lightweight, portable, and not subject to site constraints.

Prediction of spontaneous preterm birth by cervical length in the first trimester of pregnancy: Comparison of two measurement methods.

Our objectives were to compare the single-line and two-line methods of cervical length measurement in the first trimester of pregnancy and to evaluate the potential value of the first trimester cervical length measured by the two methods in predicting spontaneous preterm birth. This was a prospective study in singleton pregnancies at 11+0 to 13+6 weeks of gestation. Cervical length was measured by two methods: (i) a linear distance between the two ends of the glandular area around the endocervical canal (single-line method) and (ii) a sum of a linear distance from the internal os to the greatest cervical curvature and a linear distance from this point of the cervix to the external os (two-line method). The screening performance of the first trimester cervical length measured by the two different methods for the prediction of spontaneous preterm delivery was assessed by receiver-operating characteristics (ROC) curve analysis. The areas under the ROC (AUROC) were compared by De Long test. A total of 1484 consecutive singleton pregnancies were included in this study. Spontaneous preterm delivery at <37and <32weeks occurred in 75 cases (5.1%) and 12 cases (0.8%), respectively. The median cervical length measured by the single-line method was significantly shorter than that by the two-line method (33.5vs 36.5mm, p<.001). Compared with the term delivery group, the median cervical length measured by the two-line method was shorter in women with spontaneous delivery at <32weeks of gestation (36.5vs 33.6mm, p<.01). No significant difference in the median cervical length measured by the single-line method was detected between the spontaneous preterm delivery and term delivery groups. Receiver-operating-characteristic curves demonstrated that cervical length measured by the two-line method achieved better performance in predicting spontaneous delivery at <32weeks compared with the single-line method (AUROC: 0.72 vs 0.61, p<.01). We have demonstrated that the first trimester cervical length, measured by the two-line approach, holds promise as a potential screening tool for early spontaneous preterm delivery.

Thickness Estimation of TiO&lt;sub&gt;2&lt;/sub&gt;-Based Nanotubes Using X-Ray Diffraction Techniques

TiO2-based nanotubes are a very promising material with many applications in solar cells, biomedical devices, gas sensors, hydrogen generation, supercapacitors, and lithium batteries, among others. Nanotube thickness is a very important property since it is related to electronic and surface mechanics. In this sense, transmission electron microscopy (TEM) can be used. However, it can be difficult to acquire a good TEM image because the transversal section of the nanotubes needs to be visible. In this work, TiO2-based nanotubes obtained via hydrothermal synthesis were studied using X-ray line profile analysis. Scherrer and Single-Line methods provided consistent results for the thickness of the nanotubes (≃ 5 nm) when compared with TEM. Additionally, Single-Line method was also applied to estimate the microstrain. The advantage of using XRD is given by the fact that it is a quick and statistically significant analysis when compared with TEM. The results show that XRD can be used as a rapid and reliable alternative for the thickness estimation of nanotubes.

Magnetic Field of the Ap Star 33 Lib: A Study in Different Spectral Lines

Ap stars are chemically peculiar, main-sequence stars with atmospheres having an anomalous chemical composition (compared to the solar one). This abnormal chemical composition is thought to result from diffusion of chemical elements under the influence of radiation pressure and gravitational settling. Depending on the prevailing process, a chemical element either sinks and is accumulated in deeper layers or floats up to the upper layers of the stellar atmosphere. In addition to nonuniform depth distributions of elements, peculiar stars feature spots on their surface enriched or depleted with certain chemical elements. Ap stars have strong global magnetic fields with intensities ranging from several hundred millitesla to several tesla. These fields, as a rule, have a simple dipole configuration that remains stable over time intervals of several decades at the least. One of the unexplored effects observed in chemically peculiar stars is the significant difference in magnetic fields measured using different spectral lines. The present study is focused on measurements of the longitudinal magnetic field of the chemically peculiar Ap star 33 Lib in N = 180 spectral lines. High-resolution circularly polarized spectra collected over four nights in 2006 with the 3.6 m CFHT ESPaDOnS spectrograph were taken from the CADC open database. The magnetic field was calculated based on the Zeeman effect using the single-line method. It was found that the longitudinal magnetic field of 33 Lib averaged over all nights is 〈Be〉 = 274.9 ± 2.7 mT. Statistically significant differences between the magnetic-field magnitudes determined for different spectral lines (including those of the same chemical element) were also found. The weakest magnetic field was measured in the cores of hydrogen lines Hα and Hβ and in Y and Pr lines. The dependence of the magnetic-field magnitude on parameters of spectral lines revealed that weak lines with small Lande factors had the strongest magnetic field. This may be attributed to the nonuniformity of the magnetic field in the stellar atmosphere and the distribution of chemical elements over the surface (and/or with depth) or to both these factors.

Spatially resolved temperature measurement in the carbon dioxide arc under different gas pressures.

Carbon dioxide (CO2) is a promising alternative to sulfur hexafluoride for high-voltage circuit breaker applications. It is important to have a detailed understanding of CO2 arc properties. In this paper, radial temperature distribution of the free burning direct current arc in pure CO2 was investigated. Optical emission spectrometry was applied under different pressures (0.5atm, 1atm, and 1.5atm) and at different axial positions (1mm, 2mm, 3mm above the cathode). Assuming local thermodynamic equilibrium, the Fowler-Milne method was adopted for O I 715.67nm and O I 777.19nm in the periphery of the arc, and the single-line method was adopted for C II 657.81nm near the center of the arc. Radial temperature profiles obtained by these two methods were combined at the position where normal temperature was assigned. The results indicate that near the center of the arc, higher pressure would lead to lower temperature; as the distance from the cathode to the position measured increases, the maximum temperature in the arc center would decrease. In addition, the temperature would decrease more sharply toward the periphery if the central temperature of the arc is higher.

Dem simulation of wetting deformation characteristics of rockfill considering particle breakage

Rockfill materials are widely used in civil engineering, such as dams, railways, and airport foundations in mountain areas. Significant wetting deformation may affect the serviceability or even the safety of rockfill infrastructure. Particle breakage is an important reason for wetting deformation. However, the relation between particle breakage and wetting deformation remains unclear and further study is necessary. The discrete element method was used to simulate single-line and double-line wetting tests, and the differences between the two methods were discussed. The relationships between particle breakage characterized by Hardin index, strain and friction energy were analyzed. Furthermore, the effect of wetting path, particle shape and softening coefficient on wetting deformation were investigated. The preliminary results showed that the wetting deformation increased with the stress applied, and larger wetting deformation was observed with the single-line method. During the loading process, particle breakage mainly occurs at the corners of particles. Angular particles experience more breakages and larger wetting deformation under one-dimensional compression than rounded particles. Moreover, the relationship between the Hardin index and friction energy dissipation is affected by the wetting path, while the relation between Hardin index and the strain is unique and depends exclusively on the initial density and intrinsic parameters of the material.

Triaxial Wetting Test on Rockfill Materials under Stress Combination Conditions of Spherical Stress p and Deviatoric Stress q

A GCTS medium‐sized triaxial apparatus is used to conduct a single‐line method wetting test on three kinds of rockfill materials of different mother rocks such as mixture of sandstone and slate, and dolomite and granite, and the test stress conditions is the combination of spherical stress p and deviatoric stress q. The test results show that (1) for wetting shear strain, the effects of spherical stress p and deviatoric stress q are equivalent, and wetting shear strain and deviatoric stress q show the power function relationship preferably. (2) For wetting volumetric strain, the effect of deviatoric stress q can be neglected because it is extremely insignificant, and spherical stress p is the main influencing factor and shows the power function relationship preferably. (3) The wetting strains decrease significantly with the increase in initial water content and sample density generally, but the excessively high dry density will increase the wetting deformation. Also, the wetting strains will decrease with the increase in the saturated uniaxial compressive strength and average softening coefficient of the mother rock. Based on the test results, a wetting strain model is proposed for rockfill materials. The verification results indicate that the model satisfactorily reflects the development law of wetting deformation.

High-pressure study of Ti50Ni25Fe25 powder produced by mechanical alloying

A nanostructured Ti50Ni25Fe25 phase (B2) was formed by mechanical alloying and its structural stability was studied as a function of pressure. The changes were followed by X-ray diffraction. The B2 phase was observed up to 7 GPa; for larger pressures, the B2 phase transformed into a trigonal/hexagonal phase (B19) that was observed up to the highest pressure used (18 GPa). Besides B2 and B19, elemental Ni or a SS-(Fe,Ni) and FeNi3 were observed. With decompression, the B2 phase was recovered. Using in situ angle-dispersive X-ray diffraction patterns, the single line method was applied to obtain the apparent crystallite size and the microstrain for both the B2 and the B19 phases as a function of the applied pressure. Values of the bulk modulus for the B2, B19, elemental Ni or SS-(Fe,Ni) and FeNi3 phases were obtained by fitting the pressure dependence of the volume to a Birch–Murnaghan equation of state (BMEOS).

High-precision measurements of global stellar magnetic fields

This paper presents a brief history of the development of devices and techniques for high-precision measurements of stellar magnetic fields. Two main approaches for the processing of spectral-polarimetric observations are described: the method of least-squares deconvolution (LSD), which is used to find a mean-weighted average of the normalized polarization profile using a set of spectral lines, and a method in which each individual spectral line is used to determine the magnetic field, viz., the single line method (SL). The advantages and disadvantages of the LSD and SL methods are discussed.

Numerical Simulation Study on Slaking Deformation Properties of High Earth Core Dam

The initial soaking of coarse-grained soil will trigger significant slaking deformation of this material. In order to study the slaking deformation of a certain dam during impounding process and its impacts on the dam body, we have adopted the slaking constitutive model by singe-line method and relevant test parameters from Changjiang River Scientific Research Institute, and conducted numerical simulation on the whole process from rock filling to impounding and slaking process of high earth core rockfill dam. The result has shown that, after considering slaking deformation of upstream shell materials, the upstream settlement is generally larger than downstream settlement on the same horizontal line, and the settlement of downstream shell materials generally stays unchanged after considering slaking deformation; at the early impounding period, the settlement of dam body is increasing, and the horizontal displacement of upstream side shell materials is pointing towards upstream. These findings can adequately explain the slaking deformation of the dam caused by impoundment, testify the new slaking constitutive model by single-line method and relevant test parameters, and provide reasonable basis for engineering design.

Magnetic and Structural Characterization of Nanostructured MgFe2O4 Synthesized by Combustion Reaction

Magnesium ferrites (MgFe2O4) are ceramic oxides with spinel-type crystalline structure; they have interesting technological properties. The aim of this study was to obtain nanostructured MgFe2O4 through solution combustion synthesis using iron nitrate and magnesium nitrate as precursors and glycine as fuel, without the necessity of subsequent heat treatments after synthesis. The temperature variation with respect to a sample with constant molar ratio was investigated. The crystallinity (phases present and crystallite size: estimated by single-line method) of the products obtained was determined by X-ray diffraction, the specific surface area by the nitrogen/helium adsorption method, the morphology by transmission electron microscopy, and magnetic measurements by a superconducting quantum interference device. The synthesis method facilitated the production of magnesium ferrite with crystallite sizes between 18 and 61 nm, and the magnetic hysteresis curves indicated a ferromagnetic behavior of the samples at room temperature.

The “state of the art” of the diffraction analysis of crystallite size and lattice strain

Abstract This paper addresses both old, but “renovated” methods and new methods for diffraction line-profile analysis. Classical and even extremely simple single-line methods for separating “size” and “strain” broadening effects have merit for characterization of the material imperfectness, but it is generally very difficult to interpret the data obtained in terms of microstructure parameters as used in materials science. Developments of recent years, focusing on distinct anisotropic line-broadening effects, as due to the type, orientation and distribution of dislocations and minute compositional variation, will be touched upon. The most promising development may be the synthesis of line profiles on the basis of a microstructure model and application of the (kinematical) diffraction theory without any further assumption, which contrasts with the other methods. This approach can in principle be applied in single-line and multiple-line variants and also in analyses of the whole diffraction pattern. The advantage is the direct evaluation of microstructure parameters as used in materials science. The challenge is to develop microstructure models which are flexible enough to be applicable in more than one case ...

Thermal Residual Strain in Metallic Samples Subjected to Heating-cooling Cycles: Crystallite Size and Residual Stress Contribution to the X-Ray Profile Broadening

Metallic samples subjected to heating-cooling cycles present Thermal Residual Strain. X-ray diffraction tests showed that the samples after the cycles change in line-profile width. By increasing the maximum cycle temperature, at first, a profile broadening occurs relative to the width observed before the cycles, then a narrowing, when the temperature overcomes a certain value that is proper of each metal. An accurate analysis of the diffraction line profiles was performed on copper samples in order to distinguish the effect on the line width produced by the crystallite size with respect to that produced by residual stresses. At first, our analysis was restricted to one reflection from a (hkl) plane, so, a single-line method for the analysis of X-ray diffraction line width was adopted. Then, the methods for line profile analysis, in which two orders of reflection are considered, were also applied and the experimental results are presented together with those obtained with one reflection.

Applications of X-ray Diffraction Crystallite Size/Strain Analysis to Seismosaurus Dinosaur Bone

AbstractRecently, the remains of a giant Cretaceous Sauropod (~150 My old) were discovered in the Morrison Formation west of Albuquerque, New Mexico. This dinosaur, tentatively named Seismosaurus, was found in an exceptional state of preservation. Although it has been known since the 180Q's that fossilized bone is often composed of the mineral apatite, very few studies have been conducted to characterize farther the fossilized material. In an effort to gain insight into the state of preservation and Hie processes occurring in the bone since deposition, apatite in bone from Seismosaurus was compared with that from a contemporary elk from the Jemez Mountains, New Mexico, and with well-crystallized mineral apatite using X-ray powder diffraction and profile analysis techniques. Crystallite size/strain analyses were conducted using the Scherrer equation, the Warren-Averbaca and single-line methods, and the Rietveld method using the program GSAS. Heating the contemporary elk bone produced a decrease in the full-width-at-half-maximum (FWHM) of the reflections in the diffraction pattern. This decrease in FWHM is due to a decrease in microstrain along with a minor increase in crystallite size. Results from crystallite size/strain analysis show that both Seismosaurus and contemporary elk bone crystallites are elongate parallel to the c-axis. However, Seismosaurus bone crystallites are larger (-20-65 nm) with less strain than the contemporary elk bone crystallites (-8-20 nm), suggesting that if elk bone is an appropriate analog, then Seismosaurus bone must have undergone recrystallization.

Investigations on supermolecular structure of poly(ethylene terephthalate) samples of higher modulus

The supermolecular structure of higher modulus poly(ethylene terephthalate) (PET) samples obtained by means of multi-stage combined cold drawing/hot zone drawing procedures is characterized using WAXS, SAXS and mechanical methods. The direct separate determination of crystallite sizes and lattice distortions using a single line method has been applied for the first time to high modulus PET samples. Influences of supermolecular structure on the axial elastic modulus and on a limitation in preparing high modulus PET samples are discussed.

An improved single-line method for the wide-angle X-ray scattering profile analysis of polymers

A modified single-line technique for determining separately the size and lattice distortion parameters of the crystalline regions by wide-angle X-ray scattering (WAXS) of typical polymer materials is proposed. The efficiency of the method is demonstrated by model calculations. Furthermore, the improved single-line treatment is applied to experimentally gained WAXS profiles of polyethylene, for which, for comparison, a standard two-line profile analysis was also applied. Two alternative single-line methods presented in the literature for the investigation of metal WAXS profiles are taken into consideration.

Morphology, Composition, and Residual Stresses of Compound Layers of Nitrocarburized Iron and Steels

Specimens of pure iron, an iron-carbon (1 wt-%C) alloy, and steels Ck 45 and En 40B (=24CrMo13) were salt bath nitrocarburized. M etallographic examination was performed after Murakami etching. This etchant provides a sensitive discrimination between pure nitrides and carbon containing nitrides (carbonitrides). Thus the two-phase (ε and γ’) constitution, as well as the carbon concentration profile within the compound layer, was revealed. Nitrogen, carbon, oxygen, and sulphur concentration profiles were quantitatively determined by electron microprobe analysis. Residual stress measurement and phase analysis were carried out by X-ray diffraction methods. Both macros trains (by analysis of line shift using the sin2 Ψ method) and microstrains (by analysis of line broadening using a Voigt single-line method) were determined. In view of a possible interaction between residual stresses in the compound layer and the diffusion zone, residual stresses were also determined in the diffusion zone beneath the compound layer. The results obtained provide a basis for a model to describe the constitution of the compound layer.