Correlation In Conjunction Research Articles

A study on residual stress measurement by DIC approach in FSW welded AA6082 joints

Aluminum Alloy is extensively used in aerospace and automotive industry due to its light weight and high strength properties. It is generally joined using Friction Stir Welding, which is a solid-state process. During this process residual stresses are developed in the welded region. It is a critical factor affecting the performance and lifespan of welded parts. Accurate measurement of residual stress is very important for ensuring the structural integrity of welded components. The conventional blind hole drilling method for residual stress estimation using the strain rosette, results error in the strain data capturing and compensating it is a challenging task. The omission of strain rosette is possible using the recently developed Digital Image Correlation in conjunction with Blind Hole Drilling. This paper focuses on the feasibility study of DIC in residual stress measurement. To accomplish this, Aluminum alloy AA6082 friction stir welded butt-joints are prepared. The residual stresses were measured at the top side of the weld joint using the DIC-BHD approach. At the weld top position, the transverse residual stress of -100 MPa approx. and the longitudinal residual stress of 118 MPa approx. were estimated.

Bloodstain tails: Asymmetry aids reconstruction of oblique impact

In the field of forensic science, elongated bloodstains formed from oblique impact of droplets are sometimes used to reconstruct aspects of a bloodletting event. For low impact angles, these stains can include an asymmetric tail that bloodstain analysts can use qualitatively to establish directionality. Quantitative analysis of these bloodstain tails, and any insight that they can provide into the impact dynamics, is lacking due to experimental challenges. Previous studies of bloodstain shapes have predominantly focused on relatively large drip drops that fall vertically on flat and inclined surfaces; yet, for inclinations that produce low impact angles, gravitational effects can reshape and obscure tails, preventing insight into how tails develop on horizontal surfaces. Here, we carry out systematic experiments in which human blood droplets with diameters less than a millimeter impact a horizontal surface at impact angles ranging from 16° to 65°. High-speed imagery confirms that the tail is not part of a prompt splashing event, but rather forms at the last moments of spreading, maintaining its shape as it dries. For each stain, we link the tail length and elliptical geometry to the blood drop size and impact velocity vector that created it. Additionally, we report a power-law correlation of the dimensionless tail length with the angle and Weber and Reynolds numbers, and we describe how this correlation in conjunction with other existing correlations can improve reconstruction of the droplet size and impact velocity.

Examining power dynamics in global health governance using topic modeling and network analysis of Twitter data

ObjectivesDespite increases in global health actors and funding levels, health inequities persist. We empirically tested whether global health governance (GHG) operates under the rational actor model (RAM) and characterised GHG...

Damage accumulation mechanisms during dynamic compressive failure of boron carbide

This paper explores the compressive response of two grades of boron carbide across a range of strain rates between 102 to 103 s−1. Using ultra-high-speed photography to perform digital image correlation in conjunction with strain gauges, the evolution of apparent elastic moduli was tracked through the failure process. Analysis of damage metrics shows that the two most important measures of damage accumulation in these materials are apparent changes to shear modulus and Poisson’s ratio, rather than only apparent changes to Young’s modulus as is commonly assumed in the literature. For one grade of the boron carbide the range of strain-rates studied also included a transition from quasi-static-type failure behavior where bulking was not a significant factor, to dynamic-type failure where bulking became a significant influence on failure; this transition was linked to material-specific fracture mechanisms. For the other grade of boron carbide, only dynamic-type failure was seen in this strain-rate range, suggesting that the transition point was at a lower strain-rate.

Modeling of liftoff heights of non-premixed turbulent flames in co-flows having various temperatures and O2 concentrations

Lifted flames in combustion furnaces are diluted with burned gas entrained into the fuel jet. The reduced concentrations of reactants resulting from this dilution increase the liftoff height, while the associated temperature increase decreases the height. The aim of the present study was to develop a premixed model capable of predicting the variation in the liftoff height resulting from entrainment. A triple concentric burner incorporating fuel gas, oxidizer and co-flow gas nozzles was employed to simulate a combustion furnace. Prior to combustion tests, the fraction of the fuel gas in the non-reactive jets forming on the burner was determined, to allow an evaluation of parameters affecting the entrainment rate of the co-flow gas. The flame liftoff height above the burner was found to increase with decreases in the O2 concentration in the co-flow gas and was decreased with increases in temperature. Three premixed models were examined: a conventional premixed model, a DP1 model including only the effect of decreasing reactant concentrations and a DP2 model including the effects of both decreasing concentrations and temperature increases. Validations of these models demonstrated that the conventional model failed to predict variations in the liftoff height at a variety of co-flow gas O2 concentrations and temperatures. The DP1 model also provided insufficient correlations between the bulk velocity and liftoff height, such that the correlation line at a high co-flow gas temperature separated from that at room temperature. In contrast, the DP2 model provided excellent correlations in conjunction with different virtual origin positions.

Knowledge of Artificial Fruit Ripening Among Consumers in Rivers State

The study investigated the knowledge of artificial fruit ripening among consumers in Rivers State. The study adopted a descriptive cross-sectional survey design. Four research questions and three null hypotheses tested at .05 alpha level guided the study. The population for the study was 2,617,600 respondents in fruit markets in Rivers State. A sample size of 1,024 fruit consumers was drawn suing multistage sampling procedure. Data were collected using a validated self-structured questionnaire titled "Knowledge of Artificial Fruit Ripening (KAFR)”. Guttman Split-Half Coefficient of 0.881 was obtained using Pearson Product Moment Correlation in conjunction with Spearman Brown correction statistics. Data were analyzed using percentage, mean, standard deviation, Chi-square, z-test, and One way Analysis of Variance. It was found that consumers had moderate knowledge of artificial fruit ripening in Rivers State. Also, male consumers, those within 31-40 years and those with tertiary education had higher knowledge of artificial fruit ripening. More so, the study revealed significant difference in knowledge among consumers in Rivers State based on gender, age and level of education. Based on the findings, the study recommended among others that; community health workers in Rivers State should organize regular heath education campaigns concerning the dangers of using chemicals for fruit ripening among consumers in Rivers State. 

Default mode network connections supporting intra-individual variability in typically developing primary school children: An EEG study.

Objective: Intraindividual variability in response time (RT) provides information about attention abilities beyond accuracy and mean RT. It could be an endophenotype for a wide range of clinical disorders and a general marker of neurological health or maladaptation. The default mode network (DMN) and the central executive and the salience networks (CEN + SN) support response stability in adults. The aim of this study was to explore the associations of resting-state connectivity of the DMN and the CEN + SN with lapses of attention in typically developing primary schoolchildren. Method: RT variability was measured by RT standard deviation in the self-paced Stroop-like Animal Size Test in 137 children aged 6-11 years. Electrophysiological signatures of the DMN and the CEN + SN were obtained using a seed-based oscillatory power envelope correlation in conjunction with beamformer spatial filtering. Results: Statistical nonparametric mapping showed that RT variability was positively associated with connectivity between the DMN and the posterior insula and the right temporal cortex (PFWE-corr < .006), suggesting that a greater focus of self-reflective internal attention may be associated with obstructed transition to an active processing mode. RT variability was negatively associated with connectivity between the DMN and the anterior cingulate and the anterior insula (PFWE-corr = .001) overlapping with the SN, which handles top-down cognitive regulation. These associations were specifically found for the anterior DMN seed in the medial prefrontal cortex, which is involved in emotion and motivational circuits. Conclusions: Default network connectivity supporting RT variability may be involved in the development of internalizing and externalizing problems in childhood. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Bottom-current depositional model and characterization of the Paraburdoo Member surrounding the Paraburdoo Spherule Layer, Hamersley Basin, Western Australia

The stratigraphy within the Wittenoom Formation’s Paraburdoo Member of the Hamersley Basin in Western Australia has lacked a significant and identifiable marker bed until the recent discovery of the Paraburdoo Spherule Layer (PSL). In this paper, we correlate this stratigraphy residing at the three known exposed locations of the PSL within the Hamersley Basin and use these correlations in conjunction with detailed observations and analyses to assess the type of sedimentation recorded by these alternating ‘sand’ and ‘mud’ beds. We also characterize in detail these same several meters of stratigraphy using the PSL as a distinctive marker bed and add to the existing depositional model of the Hamersley Basin. We find that (1) the strata surrounding the PSL was not deposited by sediment gravity flows, but rather long-acting deep-marine bottom current(s), (2) the rhythmicity recorded as alternating ‘sand’ and ‘mud’ beds is the result of increasing and decreasing current velocities, (3) grain size decreases while mud content increases to the east within the basin, (4) bed thinning occurs to the west within the basin, (5) microbial activity may be recorded in laminations in the finer-grained mud beds present within these strata, and (6) the diagenetic history changes across the Hamersley Basin.

Dynamic response of closed cell PVC foams subjected to underwater shock loading

A dynamic loading facility is developed to investigate the underwater shock response of poly vinyl chloride foams of varying densities. The shock loading facility consists of a water filled hollow cylindrical structure, with one end fully closed and the other end fitted with a nylon piston. A rigid striker is used to impact the piston, which creates an underwater shockwave. The facility is comprised of four separate sections, where the middle section is an optically clear acrylic window, and the other three sections are aluminum. The optically clear acrylic window is utilized for the employment of three-dimensional Digital Image Correlation in conjunction with high-speed photography (90,000–100,000 frames per second) to obtain full-field deformation data of the foams during shock loading. Pressure data is recorded using piezoelectric pressure sensors at different locations along the underwater shock tube. Peak pressures in the range of 1–10 MPa with exponential decays are generated by changing the striker velocity. Furthermore, quasi-static hydrostatic response of pre shocked foams is evaluated using a previously developed underwater loading facility. Strain rate of 103s − 1 is obtained in foam specimens during the experiments. Findings showed substantial delay between the underwater shock loading and material response. Polyvinyl chloride foams recovered 80–90% of their original shape after underwater shock loading and also retained much of their energy absorption capacity.

Hyfraxins A and B, cytotoxic ergostane-type steroid and lanostane triterpenoid glycosides from the invasive ash dieback ascomycete Hymenoscyphus fraxineus

A virulent culture of Hymenoscyphus fraxineus, the causal agent of ash dieback, was investigated for its production of secondary metabolites in a 70 L batch fermentation. Chemical analysis of the mycelial extract by means of flash chromatography and preparative HPLC led to the isolation of a new ergostane-type steroid (1) and a new related lanostane triterpenoid (2), both revealing the same glycosylation pattern. While their planar structures were elucidated by HR-ESIMS and NMR data, relative stereochemistry was assigned by ROESY correlations in conjunction with H,H and C,H coupling constants. Absolute configuration was determined based on ROESY correlations between the aglycons and the sugar moieties, which were identified in both cases as d-mannose by GC/MS analysis of the trimethylsilylated derivatives. The isolated compounds, for which we propose the trivial names hyfraxins A (1) and B (2), were found to be cytotoxic against the mouse fibroblast cell line L929 and exhibited moderate to weak activity against Gram-positive bacteria.

Effortful control and resting state networks: A longitudinal EEG study

Resting state networks’ (RSNs) architecture is well delineated in mature brain, but our understanding of their development remains limited. Particularly, there are few longitudinal studies. Besides, all existing evidence is obtained using functional magnetic resonance imaging (fMRI) and there are no data on electrophysiological correlates of RSN maturation. We acquired three yearly waves of resting state EEG data in 80 children between 7 and 9years and in 55 adults. Children’s parents filled in the Effortful Control (EC) scale. Seed-based oscillatory power envelope correlation in conjunction with beamformer spatial filtering was used to obtain electrophysiological signatures of the default mode network (DMN) and two task-positive networks (TPN). In line with existing fMRI evidence, both cross-sectional comparison with adults and longitudinal analysis showed that the general pattern of maturation consisted in an increase in long-distance connections with posterior cortical regions and a decrease in short connections within prefrontal cortical areas. Latent growth curve analysis showed that EC scores were predicted by a linear increase over time in DMN integrity in alpha band and an increase in the segregation between DMN and TPN in beta band. These data confirm the neural basis of observed in fMRI research maturation-related changes and show that integrity of the DMN and sufficient level of segregation between DMN and TPN is a prerequisite for appropriate attentional and behavioral control.

High level of serum cholesteryl ester transfer protein in active hepatitis C virus infection.

To determine the significance of cholesteryl ester transfer protein (CETP) in lipoprotein abnormalities in chronic hepatitis C virus (HCV) infection. We evaluated the significance of the serum concentration of CETP in 110 Japanese patients with chronic HCV infection. Fifty-five patients had active HCV infection, and HCV eradication had been achieved in 55. The role of CETP in serum lipoprotein abnormalities, specifically, in triglyceride (TG) concentrations in the four major classes of lipoproteins, was investigated using Pearson correlations in conjunction with multiple regression analysis and compared them between those with active HCV infection and those in whom eradication had been achieved. The serum CETP levels of patients with active HCV infection were significantly higher than those of patients in whom HCV eradication was achieved (mean ± SD, 2.84 ± 0.69 μg/mL vs 2.40 ± 1.00 μg/mL, P = 0.008). In multiple regression analysis, HCV infection status (active or eradicated) was an independent factor significantly associated with the serum CETP level. TG concentrations in low-density lipoprotein (mean ± SD, 36.25 ± 15.28 μg/mL vs 28.14 ± 9.94 μg/mL, P = 0.001) and high-density lipoprotein (HDL) (mean ± SD, 25.9 ± 7.34 μg/mL vs 17.17 ± 4.82 μg/mL, P < 0.001) were significantly higher in patients with active HCV infection than in those in whom HCV eradication was achieved. The CETP level was strongly correlated with HDL-TG in patients with active HCV infection (R = 0.557, P < 0.001), whereas CETP was not correlated with HDL-TG in patients in whom HCV eradication was achieved (R = -0.079, P = 0.56). Our results indicate that CETP plays a role in abnormalities of lipoprotein metabolism in patients with chronic HCV infection.

A mixed Euler–Euler/Euler–Lagrange approach to erosion prediction

Providing quantitative assessment of erosion in the various parts of a piping system is of considerable importance in the oil&gas industry. Field and lab erosion testing are extremely onerous and, for this reason, this task is typically achieved by means of algebraic erosion correlations in conjunction with CFD two-phase models based on the Euler–Lagrange approach for flow computation. However, the high computational burden makes this approach onerous even for relatively simple benchmark cases, and it cannot be actually applied in many practical applications. In this paper, we present an innovative approach to erosion prediction, which relies on the combined use of Euler–Euler and Euler–Lagrange CFD two-phase models. The strength of the proposed approach, compared to the standard practice, resides in its numerical efficiency, arising from the fact that the Lagrangian description of the solid phase is restricted to certain subdomains bounded by the surfaces most vulnerable to erosion. The outcomes of two application cases, namely an abrasive jet impingement test and a simplified model of a needle and seat choke valve, demonstrate that the new approach allows considerable reduction of the computational burden for particle tracking and wear estimation. This will open the way for addressing more complex flows of considerable interest in practical applications, which are actually precluded at present.

Electromagnetic gauge field interpolation between the instant form and the front form of the Hamiltonian dynamics

We present the electromagnetic gauge field interpolation between the instant form and the front form of the relativistic Hamiltonian dynamics and extend our interpolation of the scattering amplitude presented in the simple scalar field theory to the case of the electromagnetic gauge field theory with the scalar fermion fields known as the sQED theory. We find that the Coulomb gauge in the instant form dynamics (IFD) and the light-front gauge in the front form dynamics, or the light-front dynamics (LFD), are naturally linked by the unified general physical gauge that interpolates between these two forms of dynamics and derive the spin-1 polarization vector for the photon that can be generally applicable for any interpolation angle. Corresponding photon propagator for an arbitrary interpolation angle is found and examined in terms of the gauge field polarization and the interpolating time ordering. Using these results, we calculate the lowest-order scattering processes for an arbitrary interpolation angle in sQED. We provide an example of breaking the reflection symmetry under the longitudinal boost, $P^z \leftrightarrow -P^z$, for the time-ordered scattering amplitude in any interpolating dynamics except the LFD and clarify the confusion in the prevailing notion of the equivalence between the infinite momentum frame (IMF) and the LFD. The particular correlation found in our previous analysis of the scattering amplitude in the simple scalar field theory, coined as the J-shaped correlation, between the total momentum of the system and the interpolation angle persists in the present analysis of the sQED scattering amplitude. We discuss the singular behavior of this correlation in conjunction with the zero-mode issue in the LFD.

An Experimental Investigation into Additive Manufacturing-Induced Residual Stresses in 316L Stainless Steel

Additive manufacturing (AM) technology provides unique opportunities for producing net-shape geometries at the macroscale through microscale processing. This level of control presents inherent trade-offs necessitating the establishment of quality controls aimed at minimizing undesirable properties, such as porosity and residual stresses. Here, we perform a parametric study into the effects of laser scanning pattern, power, speed, and build direction in powder bed fusion AM on residual stress. In an effort to better understand the factors influencing macroscale residual stresses, a destructive surface residual stress measurement technique (digital image correlation in conjunction with build plate removal and sectioning) has been coupled with a nondestructive volumetric evaluation method (i.e., neutron diffraction). Good agreement between the two measurement techniques is observed. Furthermore, a reduction in residual stress is obtained by decreasing scan island size, increasing island to wall rotation to 45 deg, and increasing applied energy per unit length (laser power/speed). Neutron diffraction measurements reveal that, while in-plane residual stresses are affected by scan island rotation, axial residual stresses are unchanged. We attribute this in-plane behavior to misalignment between the greatest thermal stresses (scan direction) and largest part dimension.

Morphometric growth relationships of the immature human mandible and tongue

The masticatory apparatus is a highly adaptive musculoskeletal complex comprising several relatively independent structural components, which assist in functions including feeding and breathing. We hypothesized that the tongue is elemental in the maintenance of normal ontogeny of the mandible and in its post-natal growth and development, and tested this using a morphometric approach. We assessed tongue and mandibular measurements in 174 (97 male) human cadavers. Landmark lingual and mandibular data were gathered individuals aged between 20 gestational weeks and 3 yr postnatal. In this analysis, geometric morphometrics assisted in visualizing the morphometrical growth changes in the mandible and tongue. A linear correlation in conjunction with principal component analysis further visualized the growth relationship between these structures. We found that the growth of the tongue and mandible were intrinsically linked in size and shape between 20 gestational weeks and 24 months postnatal. However, the mandible continued to change in shape and size into the 3rd yr of life, whereas the tongue only increased in size over this same period of time. These findings provide valuable insights into the allometric growth relationship between these structures, potentially assisting the clinician in predicting the behaviour of these structures in the assessment of malocclusions.

Even-parity spin-triplet pairing by purely repulsive interactions for orbitally degenerate correlated fermions

We demonstrate the stability of the spin-triplet paired s-wave (with an admixture of extended s-wave) state for the limit of purely repulsive interactions in a degenerate two-band Hubbard model of correlated fermions. The repulsive interactions limit represents an essential extension of our previous analysis (2013 New J. Phys. 15 073050), regarded here as I. We also show that near the half-filling the considered type of superconductivity can coexist with antiferromagnetism. The calculations have been carried out with the use of the so-called statistically consistent Gutzwiller approximation (SGA) for the case of a square lattice. We suggest that the electron correlations in conjunction with the Hund's rule exchange play the crucial role in stabilizing the real-space spin-triplet superconducting state. A sizable hybridization of the bands suppresses the homogeneous paired state.

Characteristic effectiveness curves for falling-film drain water heat recovery systems

Falling-film drain water heat recovery systems have proven to be a cost-effective and reliable class of heat exchanger for reducing primary energy consumption in residential and commercial buildings and in industrial buildings and processes. It is fitting, therefore, that regulatory bodies are preparing standards by which various products can be characterized, both for rating purposes and to provide data for building energy simulation. Unfortunately, standards development is progressing in the absence of measured performance data that characterize how these heat exchangers perform. The intention of the current work is to examine drain water heat recovery performance at various equal-flow conditions. The effectiveness of three drain water heat recovery systems was examined in a counter flow as a function of volumetric flow rate. The drain water heat recovery systems represented products from two manufacturers and two lengths. One of the drain water heat recovery systems was also tested in parallel flow. While the performance characteristics generally mirrored theoretical performance, there were some key differences. For the units tested, there was a clear transition region occurring between flow rates of 5 and 10 L/min (1.3 and 2.6 gpm). While the presence of this region did not impact the proposed rating process, it could significantly impact the applicability of the data analysis to building simulation. It was also shown that the number of transfer units for the collector changed significantly with flow rate, but in a predictable manner. By fitting the number of transfer units versus flow rate data, and using this correlation in conjunction with theoretical ϵ–number of transfer units equations, the drain water heat recovery performance could be well predicted over the entire range of operation.

Dynamics of Nonclassical Light from a Single Solid-State Quantum Emitter

We measure the dynamics of a nonclassical optical field using two-time second-order correlations in conjunction with pulsed excitation. The technique quantifies single-photon purity and coherence during the excitation-decay cycle of an emitter, illustrated here using a quantum dot. We observe that for certain pump wavelengths, photons detected early in the cycle have reduced single-photon purity and coherence compared to those detected later. A model indicates that the single-photon purity dynamics are due to exciton recapture after initial emission and within the same pulse cycle.

Fatigue and Serviceability Limit State Model Basis for Assessment of Offshore Wind Energy Converters

This paper develops the models for the structural performance of the loading and probabilistic characterization for the fatigue and the serviceability limit states for the support structure of offshore wind energy converters. These models and a sensitivity study are part of a risk based assessment and monitoring framework and will be applied for establishing the “as designed and constructed” reliability as prior information for the assessment and the design of monitoring systems. The constitutive physical equations are introduced in combination with the fatigue and serviceability limit state requirements as the starting point for the development of the structural performance and loading models. With these models introduced in detail, several modeling aspects for both limit states are analyzed. This includes analyses of the influence on the hot spot stresses by applying a contact formulation for the pile guide brace connection and the application of a finite element formulation using solid elements. Further, the comparison of the natural frequencies of a discrete rotor model with a continuous rotor model is documented. To account for uncertainties associated with the structural and loading models, a probabilistic model is derived on the basis of literature review and measurement data from a prototype Multibrid M5000 support structure. The sensitivity study is based on the calculation of a nonlinear coefficient of correlation in conjunction with predetermined designs of experiments. This is conducted by a systematic analysis of the influence of the random variables on limit state responses and hence on the structural reliability. Integrating the analyses and sensitivity studies of the fatigue and serviceability limit state models developed in this paper as well as the ultimate limit state models in Thöns et al. (“Ultimate Limit State Model Basis for Assessment of Offshore Wind Energy Converters,” ASME J. Offshore Mech. Arct. Eng.), the model basis for the assessment is completed. The process of establishing and analyzing such a model basis contributes to a detailed understanding of the deterministic and probabilistic characteristics of the structure and provides valuable insights in regard to the significance of available data.