Hardness Ratio Research Articles

Repeatability and Reproducibility of Potential Ultrasonographic Bishop Score Parameters.

Determination of the Bishop score (BS) is a traditional method of assessing the cervix in obstetrics and gynecology. This examination is characterized by subjectivity of assessment and low repeatability. In scientific studies intended to evaluate the results of the procedure based on the initial assessment, it is necessary to find an objective scale based on ultrasonography. We selected five ultrasound parameters, measured with a transvaginal transducer, that are equivalent to the individual BS axes (dilatation assessed in three-dimensional ultrasound (DL), angle of progression (AoP), vagino-cervical angle (VCA), strain elastography using the E-Cervix module, and cervical length (CL)). All selected parameters were characterized by good to excellent repeatability (intraclass correlation coefficient (ICC) = 0.878-0.994) and reproducibility (ICC = 0.826-0.996). Each of the selected parameters significantly correlated with its corresponding BS axis. The highest value of the correlation coefficient was achieved with CL (-0.75) and DL (0.71). Other parameters were characterized by an average to high correlation (AoP and station = 0.69, hardness ratio and consistency = -0.33, position and VCA = -0.38). The best correlation with the sum of the BS points was exhibited by AoP (0.52) and CL (-0.61). The selected ultrasound parameters analogous to the BS axes were characterized by high repeatability and significant correlation with the axes of the original clinical BS. Further research into the predictive properties of a multivariate model based on these parameters is needed.

A machine learning algorithm for reliably predicting active galactic nucleus absorbing column densities

We present a new method for predicting the line-of-sight column density (NH) values of active galactic nuclei (AGN) based on mid-infrared (MIR), soft X-ray, and hard X-ray data. We developed a multiple linear regression machine learning algorithm trained with WISE colors, Swift-BAT count rates, soft X-ray hardness ratios, and an MIR–soft X-ray flux ratio. Our algorithm was trained off 451 AGN from the Swift-BAT sample with known NH and has the ability to accurately predict NH values for AGN of all levels of obscuration, as evidenced by its Spearman correlation coefficient value of 0.86 and its 75% classification accuracy. This is significant as few other methods can be reliably applied to AGN with Log(NH < 22.5). It was determined that the two soft X-ray hardness ratios and the MIR–soft X-ray flux ratio were the largest contributors toward accurate NH determinations. We applied the algorithm to 487 AGN from the BAT 150 Month catalog with no previously measured NH values. This algorithm will continue to contribute significantly to finding Compton-thick (CT) AGN (NH ≥ 1024 cm−2), thus enabling us to determine the true intrinsic fraction of CT-AGN in the local Universe and their contribution to the cosmic X-ray background.

Building Wireless Performance Evaluation of Channel Hardening for Massive MIMO System

This letter proposes the first building wireless performance evaluation scheme considering channel hardening for an indoor massive multiple-input multiple-output (MIMO) system. We first define a metric, channel hardening obstruction (CHO), to describe the expectation value change of channel hardening ratio that a building under design (BUD) brings about. Then, the closed-form expressions are derived for the defined metric. Finally, we carry out Monte-Carlo simulations to validate the proposed scheme under various indoor scenarios, indicating the correlation between the CHO and BUD’s room amount. The proposed evaluation scheme can be used to design new or retrofit existing buildings with adequate massive MIMO performance.

Cervical elastography: finding a novel predictor for improving the prediction of preterm birth in uncomplicated twin pregnancies.

This study set out to investigate a novel ultrasound parameter using cervical elastosonography for improving the prediction of spontaneous preterm birth (sPTB) in twin pregnancies. The study was comprised of 106 twin pregnancies from October 2020 to January 2022 in Beijing Obstetrics and GynecologyHospital. They were divided into two groups according to gestational age (GA) at delivery (delivery < 35weeks and delivery ≥ 35weeks). There were five elastographic parameters: Elasticity Contrast Index (ECI), Cervical Hardness Ratio (CHR), Closed Internal cervical ostium Strain rate (CIS); External cervical ostium strain rate (ES), CIS/ES ratio and Cervical Length (CL). All of the clinical and ultrasonic indicators with P < 0.1 were considered candidate indicators via univariate logistic regression. Based on the extracted unified combination of clinical indicators, the combinations of permutation with the candidate ultrasound indicators were performed step by step in multivariable logistic regression. The best ultrasound indicator with the lowest Akaike Information Criterion (AIC) and the highest Areas Under the receiver operating characteristic Curve (AUC) was chosen for establishing the prediction score. Over 30% (36/106) of those who delivered before 35weeks gestation. There were distinct differences in the clinical characteristics and cervical elastography parameters between the two groups. Seven major clinical variables were identified as a unified clinical indicator. CISmin as the best ultrasound elastography predictor indicated the lowest AIC and the highest AUC and outperformed alternative indicators significantly in the prediction of delivery before 35weeks of gestation. Unfortunately, CLmin which was commonly used in clinical practice ranked far from all of the cervical elastography parameters and presented the highest AIC and the lowest AUC. A preliminary scoring rule was established and the ability to predict the risk of sPTB in twin pregnancies was improved (Accuracy: 0.896 vs 0.877; AIC: 81.494 vs 91.698; AUC: 0.923 vs 0.906). The cervical elastosonography predictor such as CISmin might be a more useful indicator applied for enhancing the ability in predicting twin pregnancies preterm birth than CL. Furthermore, there would be more benefits for advancing clinical decision-making in actual clinical practice by using cervical elastosonography in the near future.

Development of a mandrel indentation test to evaluate surface hardness of dimensional building stones and comparison to Vickers hardness

The present research introduces a new method namely mandrel indentation test (MIT) to evaluate surface hardness of rocks and building stones and comparing its results with the Vickers hardness test results. For performing the test, first, its apparatus was designed and built from hard and rigid steel in a turning workshop. Then, it was used on 50 common carbonate building stones including 30 limestones and 20 travertines in the laboratory. Also, surface hardness of the stones was evaluated by the Vickers hardness test. The values of mandrel indentation hardness (MIH) for the building stones were obtained between 31.75 and 113.85 kgf/mm2, and the values of Vickers hardness (HV) were obtained between 286.11 and 1361.98 kgf/mm2. The developed correlation analysis results together with the obtained Pearson, Spearman, and Kendall correlation coefficients indicated that the values of the surface hardness resulted from this approach is strongly correlated to the values of the Vickers test by a direct linear relation. The stablished simple regression analysis has confirmed the results of the correlation analysis by a determination coefficient of 0.841. Five well‐known statistical indexes were used to assess accuracy performance degree of the developed regression model. As an important finding of the research, the introduced approach has high potential and accuracy for evaluating surface hardness of the studied building stones. Finally, a classification system was proposed to classify different building stones based on their surface hardness. Based on the classification, the studied building stones are classified as very soft to moderately hard with low hardness ratio.

Evaluation of the Tensile Properties of Vanadium-Added Steels with Different Ferrite and Pearlite Hardness Ratios

Evaluation of the Tensile Properties of Vanadium-Added Steels with Different Ferrite and Pearlite Hardness Ratios

Precise determination of Young’s modulus of amorphous CuZr/nanocrystalline Cu multilayer via nanoindentation

Extracting mechanical data of thin films on rigid substrates using nanoindentation is compromised by the mechanical properties of underlying substrates, which may falsify the obtained results. With ongoing miniaturization, the substrate influence becomes more pronounced. In this study we present an experimental approach to extract the true Young’s modulus of crystalline-amorphous multilayers by means of nanoindentation. We used 1 µm thick multilayers comprised of amorphous CuZr and nanocrystalline Cu. All films were deposited onto two rigid substrate types with Young’s moduli below and above the ones expected for the deposits (film-to-substrate hardness and elastic moduli ratios between 0.3 to 1.1 and 0.6 to 1.5, respectively). Linear extrapolation of indentation data to zero indentation depth allows to precisely determine the real film’s Young’s modulus. Same investigations were performed on monolithic Cu and CuZr films of same thickness. While the hardness values change with the variation of the bilayer thickness of the multilayer structures, the Young’s modulus is not affected by the interfaces.Graphical abstract

Hardness and Depth of Cure of Conventional and Bulk-Fill Composite Resins in Class II Restorations with Transparent and Metal Matrix Strips.

Objectives: Hardness is relevant to the degree of conversion (DC) and depth of cure (DoC). The aim of this study was to determine the micro-hardness and DoC of conventional and bulk-fill composite resins in class II restorations using metal and clear matrix bands. Materials and Methods: Twelve specimens of each of the two composite resins, i.e., Filtek Z350 XT bulk-fill and Gradia posterior conventional composite, were prepared in the form of a class II cavity in a tooth mold, using a clear or metal matrix band. All specimens were cured and stored at 37°C for 24 hours. Vickers hardness was measured as a function of DoC at 2mm intervals. Data were analyzed by two-way ANOVA (alpha=0.05). Results: The bulk-fill composite exhibited significantly higher hardness levels than the conventional composite in all tested surfaces (P<0.001). However, while the metal matrix band had a significant impact on the bottom surface (P=0.059) and also on the furthest surface from the matrix and light source (P=0.04), it did not have a consistent effect across all tested surfaces. The simultaneous interaction of the composites and matrix band types in all surfaces, did not show significant differences in hardness values. The highest bottom-to-top surface hardness ratio (73%) was observed in the conventional composite near the metal matrix band. Conclusion: In deep class II cavities, the bottom-to-top surface hardness ratio did not reach the maximum of 80%, neither for bulk-fill nor conventional posterior composites. Therefore, in such cavities extended light-curing and more incremental composite placement is needed.

Influence of abrasive characteristics on the wear micro-mechanisms of NbC and WC cermets during three-body abrasion

The present study has developed new insights into the wear transition mode of cermets and provides a better understanding of the role of abrasive characteristics in three-body abrasive wear. Two sintered and fully densified cermets, NbC–Ni (NbC–12Ni–10Mo2C) and WC-Co (WC-9.5Co) with similar micro-hardness (HV30 ≈ 13.5 GPa) were selected in this study. The abrasion response of cermets against different abrasive characteristics namely size (67–245 μm), hardness (silica, alumina and SiC), and shape (round and angular) was experimentally investigated according to the ASTM G65 standard. The test results showed that the specific wear rate (SWR) of the cermets increased significantly with increasing abrasive size and hardness. The size effect shows that the dominant wear micro-mechanisms shift from binder removal (rolling) to mixed binder-carbide extrusion (sliding) as the abrasives particle size changes from smaller (67 μm) to larger (245 μm). The hardness ratio between the abrasives and cermets (Ha/Hs) highlights that silica and alumina abrasives provide mild wear (Ha/Hs < 1.5), while SiC abrasives cause severe wear (Ha/Hs > 1.5). Both cermets exhibited similar SWR during mild wear, but NbC–Ni showed 7 times higher SWR than WC-Co during severe wear. The abrasives shape effect does not show a significant difference on the wear rate of the cermets.

GRB 201015A and the nature of low-luminosity soft gamma-ray bursts

ABSTRACT GRB 201015A is a peculiarly low luminosity, spectrally soft gamma-ray burst (GRB), with T90 = 9.8 ± 3.5 s (time interval of detection of 90 per cent of photons from the GRB), and an associated supernova (likely to be type Ic or Ic-BL). GRB 201015A has an isotropic energy $E_{\gamma , \rm iso}$$= 1.75 ^{+0.60} _{-0.53} \times 10^{50}$ erg, and photon index $\Gamma = 3.00 ^{+0.50} _{-0.42}$ (15–150 keV). It follows the Amati relation, a correlation between $E_{\gamma , \rm iso}$ and spectral peak energy Ep followed by long GRBs. It appears exceptionally soft based on Γ, the hardness ratio of HR = 0.47 ± 0.24, and low-Ep, so we have compared it to other GRBs sharing these properties. These events can be explained by shock breakout, poorly collimated jets, and off-axis viewing. Follow-up observations of the afterglow taken in the X-ray, optical, and radio reveal a surprisingly late flattening in the X-ray from t = (2.61 ± 1.27) × 104 s to $t = 1.67 ^{+1.14} _{-0.65} \times 10^6$ s. We fit the data to closure relations describing the synchrotron emission, finding the electron spectral index to be $p = 2.42 ^{+0.44} _{-0.30}$ and evidence of late-time energy injection with coefficient $q = 0.24 ^{+0.24} _{-0.18}$. The jet half opening angle lower limit (θj ≥ 16°) is inferred from the non-detection of a jet break. The launch of SVOM and Einstein Probe in 2023 should enable detection of more low-luminosity events like this, providing a fuller picture of the variety of GRBs.

What Can We Learn about Compton-thin AGN Tori from Their X-Ray Spectra?&lt;sup&gt;1&lt;/sup&gt;

We have developed a Monte Carlo code for simulation of X-ray spectra of active galactic nuclei (AGN) based on a model of a clumpy obscuring torus. Using this code, we investigate the diagnostic power of X-ray spectroscopy of obscured AGN with respect to the physical properties and orientation of the torus, namely: the average column density, \(\langle N_{\textrm{H}}\rangle\), the line-of-sight column density, \(N_{\textrm{H}}\), the abundance of iron, \(A_{\textrm{Fe}}\), the clumpiness (i.e. the average number of gas clouds along the line of sight), \(\langle N\rangle\), and the viewing angle, \(\alpha\). In this first paper of a series, we consider the Compton-thin case, where both \(\langle N_{\textrm{H}}\rangle\) and \(N_{\textrm{H}}\) do not exceed \(10^{24}\) cm\({}^{-2}\). To enable quantitative comparison of the simulated spectra, we introduce five measurable spectral characteristics: the low-energy hardness ratio (ratio of the continuum fluxes in the 7–11 keV and 2–7 keV energy bands), the high-energy hardness ratio (ratio of the continuum fluxes in the 10–100 keV and 2–10 keV energy bands), the depth of the iron K absorption edge, the equivalent width of the Fe K\(\alpha\) line, and the fraction of the Fe K\(\alpha\) flux contained in the Compton shoulder. We demonstrate that by means of X-ray spectroscopy it is possible to tightly constrain \(\langle N_{\textrm{H}}\rangle\), \(N_{\textrm{H}}\) and \(A_{\textrm{Fe}}\) in the Compton-thin regime, while there is degeneracy between clumpiness and viewing direction.

The Comparative Effect of MOCAF (Modified Cassava Flour) and Corn (Zea mays L.) Flour on the Characteristics of Chiffon Cake

MOCAF is the result of processing cassava flour by fermentation, so it has better physicochemical characteristics than cassava flour. Often used as a substitute for flour in food processing, but the protein content is low. The use of MOCAF to make cakes needs to be mixed with other flour, such as corn flour to increase the protein content of cakes. This study aims to determine the effect of a mixture of MOCAF and corn flour on the characteristics of the resulting chiffon cake. Observations were made on the physical, chemical, sensory, and microbiological properties. Based on the analysis of physical, chemical, and sensory tests (color, aroma, taste, and texture) chiffon cake with a ratio of 70% MOCAF and 30% corn flour was the best treatment with moisture content (32.96%), ash (1.31). %), protein (6.34%), fat (17.14%), carbohydrates (42.20%), fiber (2.64%), a ratio of chiffon cake (93.76%), swelling power (78, 82%), color (83.45oHue), hardness (4.25 N/Cm2), microbes (3.83 log CFU/g), and mold (2.46 log CFU/g).

Study of Spectral State Transitions in Black Hole Binaries

The aim of our work is to study the origin of the spectral transitions of transient black hole binaries. In this work, we find signatures of spectral state transition (hard to soft state) while studying the radiative shock for the accretion flow. The gradient of the energy dissipation curve shows a sudden break for certain critical flow parameters when the post-shock dissipation is maximum. This particular feature is common to all spins, and the transitions are well observed. We have identified all the critical flow parameters for different black hole spins. With the dissipation, the inner edge of the disk or the geometry of the post-shock corona reduces progressively and attains a minimum for maximum dissipation. The spin enhances the maximum dissipation further. Using the exact general relativistic framework, we therefore systematically study the various dynamical properties of radiative/dissipative shocks in accretion flows to understand the observed phenomena, namely, the variation of the hard intensity emitted from the evolving Comptonizing medium, the spectral transitions, and their entanglement with the inner edge of the disk, etc. The results presented here might be useful in finding the variation of the hardness ratio and could be a first step to procuring the “q” diagram theoretically.

Bottom/top hardness ratio and dentin bonding stability of conventional and bulk-fill resin composites

Aim: To evaluate the bottom/top hardness ratio (B/T) and the dentin bonding stability of conventional and bulk-fill resin composites in high c-factor preparations. Methods: Regular conventional (Tetric N-Ceram – TNC, and Polofil Supra – PFS), regular bulk-fill (Tetric N-Ceram Bulk fill – TBF, and Admira Fusion X-tra – AFX), and low viscosity bulk-fill resin composites (Tetric N-flow – TNF, and X-tra Base – XTB) were used to restore 180 dentin conical preparations. The specimens were randomly distributed in 12 groups (n = 15) according to the resin composites and storage time-points (24 h and six months) tested. After 24 h storage, all specimens were subjected to the bottom/top hardness ratio analysis. Then, the push-out bond strength test was performed in half of the specimens and the other half were maintained for six months on water storage before testing. The failure modes were analyzed in a stereomicroscopic. The data were analyzed statistically using one- and two-way ANOVA and Tukey post-test (p &lt;0.05). Results: There were no statistically significant differences for the bottom/top hardness ratio among the resin composites (p&gt;0.05). Regardless of the storage timepoint, regular bulk-fill resin composites showed the highest bond strength values statistically (p&lt;0.05). Only conventional resin composites showed statistically lower bond strength values at six-month storage (p&lt;0.05). Adhesive failures were more predominant for low-viscosity bulk-fill resin composites. Conclusion: Although the DoC was not affected by different materials tested, only bulk-fill resin composites did not present dentin bond strength loss after six-month of water storage.

Polymerization shrinkage of light-cured conventional and bulk-fill composites -The effect of cavity depth and post-curing.

Volumetric shrinkage (VS) of conventional, bulk-fill, and core build-up resin-based composites (RBCs) of various thickness (1-5 mm) was measured using the modified bonded-disk method with confocal laser scanning microscopy. Additionally, the bottom-to-top ratio of Vickers hardness (%VH) was measured. Conventional RBCs exhibited significantly higher VS than bulk-fill and core build-up RBCs (p<0.05). As specimen thickness increased, VS relative to volume (%VS) and difference in VS at each depth (VSdepth) decreased. For conventional RBCs, there was a significant drop in VSdepth between 1 mm and 2 mm (p<0.05), and another drop was observed between 3 mm and 4 mm (p<0.05) where %VH decreased below 90%. For bulk-fill and core build-up RBCs, VSdepth decreased significantly between 2 mm and 3 mm (p<0.05), but %VH exceeded 90% even in 5 mm deep cavities. These results indicated that post-curing contributed to lower shrinkage in deeper layers, and that conventional RBCs were not adequately polymerized at the depth of over 3 mm.

Wear Resistance Prediction of AlCoCrFeNi-X (Ti, Cu) High-Entropy Alloy Coatings Based on Machine Learning

In order to save the time and cost of friction and wear experiments, the coating composition (different contents of Al, Ti, and Cu elements), ratio of hardness and elastic modulus (H3/E2), vacuum heat treatment (VHT) temperature, and wear form were used as input variables, and the wear rates of high-entropy alloy (HEA) coatings were used as output variables. The dataset was entirely obtained by experiment. Four machine learning algorithms (classification and regression tree (CART), random forest (RF), gradient boosting decision tree (GBDT), and adaptive boosting (AdaBoost)) were used to predict the wear resistance of HEA coatings based on a small amount of data. The results show that except for the GBDT model, the other three models had good performance. Because of the small amount of data, the CART model demonstrated the best prediction performance and can provide guidance for predicting the wear resistance of AlCoCrFeNi-X (Ti, Cu) HEA coatings for drilling equipment. Furthermore, the contribution of different factors to the wear rate of AlCoCrFeNi-X (Ti, Cu) HEA coatings was obtained. Al content had the greatest influence on wear rate, followed by H3/E2, wear form, and VHT temperature.

Tribological Behavior of Doped DLC Coatings in the Presence of Ionic Liquid Additive under Different Lubrication Regimes

Diamond-like carbon (DLC) coatings are widely used in industries that require high durability and wear resistance, and low friction. The unique characteristics of DLC coatings allow for the possibility of creating adsorption sites for lubricant additives through the doping process. In this study, the combined use of europium-doped diamond-like carbon (Eu-DLC), gadolinium-doped diamond-like carbon (Gd-DLC), and pure DLC coatings and an ionic liquid (IL) additive, namely, trihexyltetradecylphosphonium bis (2-ethylhexyl) phosphate [P66614] [DEHP], with a 1 wt.% concentration in polyalphaolefin (PAO) 8 as a base lubricant was investigated. Higher hardness, higher thin-film adhesion, a higher ratio of hardness to elastic modulus, and a higher plastic deformation resistance factor were achieved with the Gd-DLC coating. The CoF of the Gd-DLC coating paired with the IL was superior compared to the other pairs in all lubrication regimes, and the pure DLC coating had a better performance than the Eu-DLC coating. The wear could not be quantified due to the low wear on the surface of the DLC coatings. The friction reduction demonstrates that tribological systems combining Gd-DLC thin films with an IL can be a potential candidate for future research and development efforts to reduce friction and increase the efficiency of moving parts in internal combustion engines, for instance.

Machine Learning Applied to X-Ray Spectra: Separating Stars in Orion Nebula Cluster from Active Galactic Nuclei in CDFS

Modern X-ray telescopes have detected hundreds of thousands of X-ray sources in the universe. However, current methods to classify these sources using the X-ray data themselves suffer problems—detailed X-ray spectroscopy of individual sources is too time consuming, while hardness ratios often lack accuracy, and can be difficult to use effectively. These methods fail to use the power of X-ray CCD detectors to identify X-ray emission lines and distinguish line-dominated spectra (from chromospherically active stars, supernova remnants, etc.) from continuum-dominated ones (e.g., compact objects or active galactic nuclei, AGN). In this paper, we probe the use of artificial neural networks (ANN) in differentiating Chandra spectra of young stars in the Chandra Orion Ultradeep Project (COUP) survey from AGN in the Chandra Deep Field South (CDFS) survey. We use these surveys to generate 100,000 artificial spectra of stars and AGN, and train our ANN models to separate the two kinds of spectra. We find that our methods reach an accuracy of ∼92% in classifying simulated spectra of moderate-brightness objects in typical exposures, but their performance decreases on the observed COUP and CDFS spectra (∼91%), due in large part to the relatively high background of these long-exposure data sets. We also investigate the performance of our methods with changing properties of the spectra such as the net source counts, the relative contribution of background, the absorption column of the sources, etc. We conclude that these methods have substantial promise for application to large X-ray surveys.

Magnetic exchange coupling and effect of grain and grain boundaries on conduction mechanism of (MgFe2O4)100-x /(BaFe12O19)x nanocomposites

(MgFe2O4)100-x/(BaFe12O19)x, soft/hard nanocomposites (NCs) having different hard ferrite ratio i.e. x = 0, 25, 50, 75 and 100 have been synthesized via in-situ auto-combustion sol-gel method. XRD patterns ensured the co-existence of both hexaferrite and spinel ferrite phases without any impure phase and no significant difference in average crystallite size was observed. The FTIR and Raman spectra confirmed the fabrication of desired material without any impurity. The absence of blocking peak in the ZFC measurements revealed that the blocking temperature of these NCs lie above room temperature. The M-H loops taken at different temperatures resulted into single smooth curve indicating strong interphase exchange-coupling among hard-soft ferrite phases. The occurrence of shoulder peak in dM/dH versus H curve for molar ratio x = 50 is indication of weak exchange coupling between the two phases. From modified Block's law fitting, the Block's constant (B) exponentially declined with the addition of hard phase that revealed higher value of exchange-coupling constant J. The complex impedance analysis (Nyquist/Cole-Cole plots) and its simulation using an equivalent model circuit revealed the major contribution of both grains and grin-boundaries toward the total conduction mechanism of the NCs. These findings indicate that the higher value of impedance makes these NCs favorable candidates for numerous technological areas like electromagnetic shielding and high band-pass filters.

Influence of contact compliance of parts and the ratio of hardness of their materials on the load capacity of a bolted joint

The influence of the contact compliance of the joint of parts under different conditions of deformation of a rough surface, as well as the ratio of the hardness of the materials of the parts on the load capacity of a pre-tightened bolted joint, is considered. Keywords: surface roughness, penetration, flattening, material hardness ratio, plastic hardness. matlin@vstu.ru, kazankin_vmn@mail.ru