Change In Full Width At Half Maximum Research Articles

Multicycle flash sintering of cubic Y2O3-stabilized ZrO2: An in situ energy dispersive synchrotron x-ray diffraction study with high temporal resolution

The current induced unit cell volume changes, (111) Bragg peak full width at half maximum (FWHM) and its integrated intensity in 8 % Y2O3 stabilized ZrO2 (8 %YSZ) solid state electrolyte was monitored during a triple-flash sintering experiment by in situ energy dispersive x-ray diffraction using a polychromatic synchrotron probe (max, photon energy 200 keV) with 2 second temporal resolution. The first spontaneous singularity in the unit cell volume (+0.54 %) was observed at 899 °C under 15 V/mm applied field intensity, which was associated with 13 mA/mm2 current draw and an increase in density to 97 %. Following anelastic relaxation of the unit cell volume under open circuit conditions, the same applied field was applied twice in a row which resulted in additional induced singularities at 925 °C (+0.48 %) and 944 °C (+0.42 %). A floating baseline, which was above the thermal expansion baseline, was observed from 833 to 969 °C and was attributed to Joule heating. The singularity at 899 °C is associated with a sharp change in (111) FWHM and a 34 % decrease in integrated peak area that was attributed to changes in the distribution of oxygen vacancies and the changes in their concentration as induced by the applied field in the spontaneous transient stage of flash sintering.

Simultaneous measurement of temperature and strain using a single fiber bragg grating on a tilted cantilever beam

Importance of simultaneous measurement of temperature and strain by fiber Bragg grating (FBG) sensors has led to innovation of several renewing techniques. Most of them are based on two FBGs configurations or one non-uniform FBG implementation. Both temperature and strain changes can result in Bragg wavelength shift in reflected spectrum from a uniform FBG. We propose using full width at half maximum (FWHM) of the reflection spectrum as a cross-sensitivity indicator for simultaneous measurement of temperature and strain using only one FBG. When a non-uniform strain is applied to a sample which a uniform FBG is stuck on it, in addition to the Bragg wavelength, FWHM of the reflection spectrum changes. This FWHM change besides the Bragg wavelength shift is used to obtain simultaneously strain and temperature. When a uniform strain is applied to the sample, we get the help of cantilever beam concept. We place a ramp with an angle of θ, similar to a tilted cantilever beam, on a sample under test and stick a FBG on the ramp. A uniform strain applied to the sample, creates a strain gradient along the cantilever beam and of course along the FBG causing a change in the FWHM of reflection spectrum. This FWHM change besides the Bragg wavelength shift is used to obtain simultaneously strain and temperature. In our simulation results, temperature sensitivity of the FBG is 14.2 pm/℃ for Bragg wavelength with no change in the FWHM and strain sensitivity is 0.453 pm/μe for Bragg wavelength and a nonlinear sensitivity according to a quadratic function for FWHM variation.

Effect of shot peening time on δ/γ residual stress profiles of AISI 304 weld

Abstract δ ferrite and residual stress are known to affect the corrosion behavior of AISI 304 stainless steel welds. To improve the corrosion resistance of a weld, shot peening is often carried out. This study aimed to investigate the effect of shot peening time on the residual stress evolution in both δ ferrite and γ austenite in a 304 stainless steel weld. The residual stresses of both δ and γ phases were significantly transformed from tensile to compressive after shot peening, and in addition, their surface residual stress deviations were lowered as the peening time increased. The stress versus depth profiles revealed a distinct plastic zone and an effective peening depth. The full width at half maximum (FWHM) of both phases increased as the peening time increased, but that of δ reached to a near stable value at peening 4 min. The FWHM change might be an index of surface coverage of peening, depending on the alloy phases. The electrochemical testing showed that shot peening effectively reduced the corrosion current intensity (Icorr) of the weld to a lower value than that in welds peened by other processes. Both the grain refinement and compressive stress enhanced the corrosion resistance of the weld.

Temperature and Emissivity Inversion Accuracy of Spectral Parameter Changes and Noise of Hyperspectral Thermal Infrared Imaging Spectrometers

The emergence of hyperspectral thermal infrared imaging spectrometers makes it possible to retrieve both the land surface temperature (LST) and the land surface emissivity (LSE) simultaneously. However, few articles focus on the problem of how the instrument’s spectral parameters and instrument noise level affect the LST and LSE inversion errors. In terms of instrument development, this article simulated three groups of hyperspectral thermal infrared data with three common spectral parameters and each group of data includes tens of millions of simulated radiances of 1525 emissivity curves with 17 center wavelength shift ratios, 6 full width at half maximum (FWHM) change ratios and 6 noise equivalent differential temperatures (NEDTs) under 15 atmospheric conditions with 6 object temperatures, inverted them by two temperature and emissivity separation methods (ISSTES and ARTEMISS), and analyzed quantitatively the effects of the spectral parameters change and noise of an instrument on the LST and LSE inversion errors. The results show that: (1) center wavelength shifts and noise affect the inversion errors strongly, while FWHM changes affect them weakly; (2) the LST and LSE inversion errors increase with the center wavelength shift ratio in a quadratic function and increase with FWHM change ratio slowly and linearly for both the inversion methods, however they increase with NEDT in an S-curve for ISSTES while they increase with NEDT slightly and linearly for ARTEMISS. During the design and development of a hyperspectral thermal infrared instrument, it is highly recommended to keep the potential center wavelength shift within 1 band and keep NEDT within 0.1K (corresponding LST error < 1K and LSE error < 0.015) for normal applications and within 0.03K (corresponding LST error < 0.5K and LSE error < 0.01) for better application effect and level.

Use of a Total Variation Minimization Iterative Reconstruction Algorithm to Evaluate Reduced Projections during Digital Breast Tomosynthesis.

Purpose We evaluated the efficacies of the adaptive steepest descent projection onto convex sets (ASD-POCS), simultaneous algebraic reconstruction technique (SART), filtered back projection (FBP), and maximum likelihood expectation maximization (MLEM) total variation minimization iterative algorithms for reducing exposure doses during digital breast tomosynthesis for reduced projections. Methods Reconstructions were evaluated using normal (15 projections) and half (i.e., thinned-out normal) projections (seven projections). The algorithms were assessed by determining the full width at half-maximum (FWHM), and the BR3D Phantom was used to evaluate the contrast-to-noise ratio (CNR) for the in-focus plane. A mean similarity measure of structural similarity (MSSIM) was also used to identify the preservation of contrast in clinical cases. Results Spatial resolution tended to deteriorate in ASD-POCS algorithm reconstructions involving a reduced number of projections. However, the microcalcification size did not affect the rate of FWHM change. The ASD-POCS algorithm yielded a high CNR independently of the simulated mass lesion size and projection number. The ASD-POCS algorithm yielded a high MSSIM in reconstructions from reduced numbers of projections. Conclusions The ASD-POCS algorithm can preserve contrast despite a reduced number of projections and could therefore be used to reduce radiation doses.

Design and Fabrication of Lossy Mode Resonance Based U-Shaped Fiber Optic Refractometer Utilizing Dual Sensing Phenomenon

The present work for the first time, provides a detailed analysis of U-shaped lossy mode resonance (U-LMR) fiber optic refractometer which is based on dual sensing phenomena. Theoretical and experimental studies on the sensitivities of U-LMR based fiber optic refractometer have been carried out utilizing different surrounding medium refractive indices (SRI). Also, the effect of bend diameter on the sensitivity has been investigated in detail by fabricating and analyzing zinc oxide (ZnO) coated U-shaped fiber optic probes of various bend diameters. Experimental sensitivities of the proposed U-LMR fiber optic refractometer were characterized in terms of wavelength shift, absorbance and full-width at half-maximum (FWHM) changes with respect to the SRI. With ZnO coated U-shaped fiber optic probe of bend diameter of 1.5 mm, we achieved six fold increase in the LMR sensitivity compared to the straight LMR probe. Also, in terms of the absorbance, our proposed probe was found to be four times sensitive compared to the uncoated U-shaped probe. In addition to this, for the probe diameter of 2.1 mm, sensitivity obtained by monitoring a new parameter, viz. FWHM change, is $\sim$ 900 nm/RIU which is at least 3 times better than the straight LMR probe.

Effects of oxygen partial pressure on the characteristics of magnetron-sputtered ZnMgBeO thin films

Effects of oxygen partial pressure within the Ar process plasma on the optical, structural, and electrical properties of magnetron-sputtered ZnMgBeO films were investigated in detail. It was observed that the optical energy bandgap (Eg) values of the ZnMgBeO films substantially decrease with the oxygen addition, from 5.3 to 4.3eV as the oxygen partial pressure increases from zero to one. The full-width-at-half-maximum (FWHM) values of the (0002) XRD peaks drastically decrease with the addition of a small amount of oxygen but then increase with further oxygen addition. All the films had very high sheet resistance, 1.3–1.4GΩ/□. It was also observed that the concentration of Zn within the films significantly increased with the oxygen addition, which was proposed to be mainly responsible for the observed decrease in Eg. It was also proposed that the FWHM change due to the oxygen addition may be attributable to three factors, film composition, grain size, and point defect density, as confirmed by results of TEM and XPS investigations.

Non-destructive Micro-structural Characterization of Metallic Specimens with a Portable X-ray Diffraction based Residual Stress Analyzer

Non-destructive characterization of surface microstructure of an engineering component is an important parameter to assess its fitness to function in the given service conditions. The paper describes various case studies performed in authors’ laboratory involving use of portable X-ray diffraction based residual stress analysis system to examine and understand the micro-structural state of the investigated surface. A significant decrease in full width at half maximum (FWHM) of gamma(311) diffraction peak from about 4.2° in the cold worked state to about 2.5° in the annealed/surface melted state was recorded for austenitic stainless steel. In case of 0.4% carbon steel there is sharp increase in FWHM of alpha(211) diffraction peak from about 2° in the as received condition to about 5-6° in the laser hardened condition. Crystallographic texture developed during electro-plating of chromium on stainless steel, could be detected from the strong intensity of alpha (211) peak of chromium at about 19° to the surface normal with respect to all other X-ray inclination angles (ѱ) during residual stress measurement. The results show that FWHM and intensity variation of the diffraction peak are two sensitive parameters for characterization of surface microstructure. Change in FWHM has been used to detect machining-induced cold deformation and evolution of re-crystallized grains in austenitic stainless steel and formation of hard martensite in laser transformation hardened ferritic steel. Variation in the intensity of diffracted peak with respect to X-ray inclination angle provided valuable information regarding crystallographic texture in hard chrome plated deposits.

System response matrix calculation using symmetries for dual‐head PET scanners

ABSTRACTPositron emission tomography (PET) scanner with dual‐head geometry offers better spatial resolution and higher sensitivity for dedicated application when compared with conventional full‐ring PET scanners. However, this configuration suffers from limited‐angle projection and depth‐of‐interaction (DOI) effects. Accurate modeling of the system response matrix (SRM) and its incorporation into iterative methods can help to obtain images with better quality. In this paper, we proposed a line‐of‐response (LOR) based symmetry approach to calculate the SRM of PET scanners with dual‐head geometry. Both Monte Carlo (MC) and analytically computed SRMs were obtained and named MC SRM and geometrical SRM respectively, with their performances been compared using simulated phantom studies. The point source study shows that the resolution in directions parallel to the detector is rather uniform, with a full width at half maximum (FWHM) of 0.6∼0.7 mm and 0.6∼0.8 mm using MC and geometrical SRMs respectively. While the spatial resolution in the direction perpendicular to the detector is much worse, when moving towards the detector panel from the field‐of‐view (FOV) center, the FWHM changes from 1.5 mm to 1.8 mm and 2.4 mm to 3.1 mm using MC and geometrical SRMs, which is caused by the missing of projection views. Images generated using MC SRM also show better stochastic quality and quantitative performance. © 2013 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 23, 205–214, 2013

Interface coherency strain relaxation due to plastic deformation in single crystal Ni-base superalloys

The micromechanical behavior under compression for a cube-oriented single crystal Ni-base superalloy was in-situ studied by synchrotron high energy X-ray diffraction at room temperature. Both elastic and plastic deformation altered the mismatch strain between γ and γ′ phases with different variances. The deformation-induced interface coherency strain relaxation was observed after yielding as evidenced by an increment of lattice mismatch and an abnormal decrease in full width at half maximum (FWHM), which is attributed to aggregating of dislocations toward phase boundaries. A dislocation-mismatch model is proposed to correlate the relative change in lattice mismatch and FWHM during deformation, which fits the experiment well.

Experimental assessment of the phonon confinement in TiO2 anatase nanocrystallites by Raman spectroscopy

TiO2 aerogels prepared by sol‐gel method and followed by supercritical drying have been annealed at temperatures ranging between 400 and 550 °C. The obtained TiO2 anatase crystallites with the mean size between 6.4 and 13.9 nm, as obtained from transmission electron microscopy measurements, have been further investigated by Raman spectroscopy. It was found that the peak position and full width at half maximum (FWHM) of the TiO2 anatase Raman bands located around 144, 398, and 638 cm−1 are influenced by crystallite dimension. These spectral changes can be assigned to the combined action of several nanosize effects such as phonon confinement, phonon coupling, strain, and stoichiometry defects. Surprisingly, the best discrimination of the FWHM change with the nanocrystallite mean size was achieved for the 638 cm−1 band, whereas the best discrimination for the peak position was found for the 398 cm−1 band. The critical size values obtained from the peak position and FWHM evaluation were between 12.7 and 13.1 nm. Taking into consideration that only the phonon confinement and inhomogeneous strain can induce an asymmetric broadening of the Raman signal, the bands asymmetry was evaluated, and the critical size values of the nanocrystallites were determined to be between 10 and 11 nm. For a symmetric size distribution of TiO2 anatase crystallites with dimensions between 6.4 and 13.9 nm, the obtained result indicates that the phonon confinement contribution to the overall size effects is more than 75%. No evidence about the influence of the phonon coupling and vacancies on the Raman features was observed. The comparison of the data derived from the experimental analysis with those obtained by applying the theoretical phonon confinement model indicates the necessity of developing an improved phonon confinement model. The asymmetry approach can be applied for a great variety of nanostructures, as a measure of the confinement effect. Copyright © 2011 John Wiley &amp; Sons, Ltd.

XPS study of Cu/substrate systems obtained by pulsed laser deposition

AbstractIn this paper XPS was used to study the evolution of Cu 2p3/2 peaks with the increase of the metal coverage on different types of substrate: Ni, HOPG (highly orientated pyrolytic graphite) and KBr. The results showed that: (i) the binding energy of the Cu 2p3/2 peak in the system Cu/HOPG decreases with surface coverage, while in the system Cu/Ni it increases; (ii) with the increase of the Cu coverage in all the systems studied a general trend of the Cu 2p3/2 peak is the reduction of FWHM (full width at half maximum), but the degree of the FWHM change depends greatly on the type of the substrate. The results obtained for binding energy change are discussed in relation to the initial and final state contributions. The results indicate that the final state contributes more to the change of the binding energy in the more 3‐dimensional structure Cu/HOPG system, while in the more 2‐dimensional Cu/Ni system the initial state contribution dominates. The FWHM change is analysed in terms of the size distribution of clusters and change of the lifetime of the holes left by the photoelectrons, which is affected by the size of the clusters and the degree of the hybridization between the s and d electrons. Copyright © 2004 John Wiley &amp; Sons, Ltd.

Compression and pressure-induced amorphization of Co(OH)2 characterized by infrared vibrational spectroscopy.

The infrared-active (${\mathit{A}}_{2\mathit{u}}$) O-H vibration of Co(OH${)}_{2}$ decreases in frequency under hydrostatic compression to 51 GPa at 290 K. Similarly, the bond anharmonicity, determined from the ${\ensuremath{\nu}}_{1}$\ensuremath{\rightarrow}${\ensuremath{\nu}}_{2}$ absorption-band difference, increases by more than a factor of 2 between 0 and 20 GPa. Both changes are attributed to an increase in the O-H bond length due to enhanced hydrogen bonding under pressure. The full width at half maximum (FWHM) of the fundamental absorption band increases abruptly by \ensuremath{\sim}100 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ at 11.2 (\ifmmode\pm\else\textpm\fi{}0.3) GPa, and continues to increase at a rate of \ensuremath{\sim}3.3 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$/GPa up to 36 GPa. Above 36 (\ifmmode\pm\else\textpm\fi{}2) GPa and below the onset of amorphization, the FWHM changes at a slower rate, 0.8 (\ifmmode\pm\else\textpm\fi{}0.1) ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$/GPa. The abrupt change in FWHM is reversible on decompression, and is interpreted in terms of a pressure-induced crystal-to-glass transition exhibiting a small hysteresis compared to similar compounds. The rapid variation in FWHM above the transition pressure suggests that the amorphous structure is continuously modified between 11.3 and 36 GPa.

Irradiation-induced texture variations and atomic displacements in Au and NbN layers

Irradiation of Au and NbN sputtered layers with 600 keV Ar2 + ions leads to a reduced orientation distribution of the [111] direction of the Au layers from a full width at half maximum (FWHM) of the orientation distribution of 12° to a FWHM of 6° and to only very small FWHM changes in the texture distributions of the NbN layers. However, the FWHM of the distribution of the reflections of the irradiated NbN layers is increased significantly from Δθ = 0.65 to 1.17° for one sample position. This is caused by small atomic displacements in the NbN lattice. The FWHM of the reflection distribution of the Au layers increased from Δθ = 0.60 to 0.65° after irradiation. Oblique incidence of Ar2 + ions causes, by absence of channeling, stronger distortions than perpendicular incidence.