Young's Modulus Of Elasticity Research Articles

The associations of depressive symptoms and perceived stress with arterial health in adolescents.

Cardiovascular and mental diseases are among the most important global health problems, but little is known on the associations between mental and arterial health in adolescents. Therefore, we investigated the associations of arterial health with depressive symptoms and perceived stress in adolescents. A total of 277 adolescents, 151 boys, 126 girls, aged 15-17 years participated in the study. Depressive symptoms were assessed using the Beck Depression Inventory and perceived stress by the Cohen Perceived Stress Scale. Arterial health was assessed by measures from carotid ultrasonography (carotid intima-media thickness, Young's Elastic Modulus, carotid artery distensibility, stiffness index), impedance cardiography (pulse wave velocity, cardio-ankle vascular index), and pulse contour analysis (reflection index, stiffness index). The data were analyzed using linear regression models adjusted for age and sex. Depressive symptoms or perceived stress were not associated with indices of arterial health in the whole study group (β = -0.08 to 0.09, p > 0.05), in boys (β = -0.13 to 0.10, p > 0.05) or in girls (standardized regression coefficient β = -0.16 to 0.08, p > 0.05). We found no associations of depressive symptoms and perceived stress with arterial health in adolescents. These observations suggest that the association between mental and arterial health problems develop in later life.

Elastic analytical method with machine learning for predicting the stratum displacement field induced by shallow tunneling

Support vector regression (SVR) with sparrow search algorithm (SSA) is developed as the machine learning (ML) model to predict maximum surface settlement smax caused by tunneling. A novel method for calibrating boundary conditions of analytical solution is proposed, where the maximum surface settlement derived by the analytical method is equal to smax predicted by SSA-SVR method. The elastic analytical solution for stratum displacement of a shallow tunnel is presented by the complex variable method, when the calibrated nonuniform displacement function is applied as the tunnel displacement boundary condition. The proposed analytical solution-machine learning (AM) method can predict the stratum displacement field prior to the tunnel excavation. Seventy-three tunnel engineering cases are employed to verify the rationality of the proposed SSA-SVR method in predicting smax. The value of R2 in the training and test process is 0.894 and 0.877, respectively. Taking Heathrow Express Trial Tunnel as an example, the potential of the proposed AM method in predicting stratum displacement is presented where the influence of cohesion strength, internal friction angle, Young's elastic modulus of stratum, tunnel radius and depth are considered. The proposed AM method can well predict the stratum surface settlement trough curve, vertical and horizontal displacement at different positions.

Influence of TiC contents on the microstructure, mechanical properties, and oxidation behavior of Mo–10Si–8B alloys

The microstructure, mechanical properties, and oxidation behavior of Mo–10Si–8B-xTiC (at.%, x = 0,5,10,15) alloys fabricated via oscillatory pressure sintering are studied. The phase constitution of three TiC-added alloys is α-Mo + Mo3Si + Mo5SiB2 + Mo2C + TiC; in 15TiC alloy α-Mo phase no longer maintains its contiguity as in the other three alloys. With further TiC addition, the microhardness improves by 60–90 % (up to 1500 HV), Young's elastic modulus increases from 328 to 368 GPa, and the fracture toughness decreases from 14.23 to 10.8 MPa m1/2, accounting for the less-ductile phase and newly introduced brittle phases. Thermogravimetric analysis indicates that the addition of TiC reduces the oxidation resistance. For isothermal oxidation at 800, 1000, and 1200 °C, the serious oxidation occurs for all TiC-added alloys except for 15TiC alloy at 1200 °C because the oxidation sequence changes to TiC → Mo5SiB2 → Mo3Si → α-Mo. The anomalous phenomenon for 15TiC alloy at 1200 °C could be attributed to the rapid formation and cover of protective SiO2–TiO2 layer on alloy surface after the transient MoO3 volatilization.

From stress concentrations between inclusions to probability of breakage: A two-dimensional peridynamic study of particle-embedded materials.

Particle-embedded materials consist of a dispersed phase of particles in a sticking matrix. We used a bond-based peridynamics method to investigate their elastic properties, rupture, and probability of failure. We performed an extensive two-dimensional parametric study where particles are disk-shaped inclusions diluted into a pore-filling matrix. Both particle and matrix are considered to be brittle elastic with a perfectly bonded interface. The inclusion volume fraction φ and the inclusion matrix toughness ratio β (β≥1) were varied from 0.254-0.754 (jamming point) and 1.5-100.0, respectively. A total of 5000 uniaxial tensile tests up to failure were performed. We showed that the Halpin-Tsai model fits well all Young elastic moduli even for nearly in-contact particles. The stress distribution strongly depends on φ and β. As the highest stresses (at the origin of crack nucleation) occur between neighboring particles, we analyzed the average stress in gaps. We found that, regardless of the particle volume fraction, the yield stress is a power law of a grain-scaled stress concentration factor. We also investigated the probability of failure of the samples. We found that whatever φ and β, this probability follows a classical Weibull law. Finally, we showed that Weibull modulus, normalized by its value for infinitely rigid particles, is inversely proportional to a function of the stress concentration factor.

Zinc as a potential bio-degradable temporary implant material

This paper discusses the possibility of developing metallic zinc (Zn) and its alloys as temporary bio-implants by improving its properties through alloying, mechanical deformations and surface modifications. Even though the research on Mg and Fe as potential temporary implant materials started over two decades ago, Zn is a comparatively newer candidate in this arena. The scope for Zn-based materials for bio-related applications is immense due to their metabolically essential status, ideal biodegradation rates and the possibility of proper excretion by the kidneys. This paper covers the unique favourable properties of Zn and its alloys, which can be explored for bio-applications, along with its limitations and possible options to overcome the limitations. The mechanical properties of Zn implants can be improved to the set standards of load-bearing applications by alloying and mechanical deformations like extrusion, rolling and severe plastic deformations. As a result, the microstructure of the metal alters by grain refinement, formation and redistribution of intermetallic phases, resulting in enhanced hardness, Young's modulus and elastic modulus of the material. The Zn implant surface can be made fully bioactive and corrosion-resistant by engineering its surfaces with biocompatible polymers, bioactive materials like hydroxyapatite and bio-inductive elements like Si. The biochemical treatments, sol–gel techniques and plasma electrolytic oxidation (PEO) processes are effective for surface modification of Zn-based materials. Alloying, mechanical treatments and surface modification techniques are reported to be effective in improving the function of Zn-based implant materials, as discussed in this paper.

Методика оцінки залежності власних частот коливань лопаток газових турбін від анізотропії монокристалу

The subject of study of this article is one of the key tasks that arises during the development and operation of aviation gas turbine engines, namely ensuring the strength of their parts. The turbine blade is one of the most heavily loaded parts of an aircraft engine. Therefore, at the stage of designing these blades, it is necessary to be able to identify and avoid possible resonance modes that appear during the flight cycle of an aircraft gas turbine engine. Such resonant oscillations of gas turbine blades can occur due to time-varying gas-dynamic forces from the action of the gas flow and are periodic in nature, as they are determined by the frequency of rotation of the rotor. In order to regulate the frequency characteristics of the blades to prevent dangerous resonant forms of oscillations that arise under the action of various harmonics of the exciting force during variable modes of operation of the aircraft engine, it is necessary to carry out a complex of various technological or structural changes. At the current stage, turbine blades of aircraft engines are manufactured by the method of single-crystal casting. As is known, single crystals have anisotropic properties, namely they manifest themselves as materials with the characteristics of cubic symmetry. A very urgent task is to investigate the effect of the anisotropy of the elastic characteristics of monocrystalline blades on their natural frequencies and forms of oscillations. In this research, the authors developed a method for determining the elastic characteristics of a single crystal, namely Young's modulus of elasticity, Poisson's ratio and pure shear modulus, which is based on available experimental data for typical heat-resistant alloys. With the help of finite element analysis on the example of a typical model of a cooled blade of a gas turbine, its modal analysis was carried out and its resonance diagram was constructed. The trend of changing the natural frequencies and forms of blade oscillations when the elastic constants of the single crystal change due to the rotation of the crystallographic system of directions was also investigated. The three-dimensional model of the blade was built using the capabilities of the NX graphics complex, all calculations were performed in the Maple computing complex, and the capabilities of the ANSYS software complex were used for finite element analysis.

Effect of water content and aging on the elastic properties of extruded pea protein isolate

The effects of water on the elastic properties of extruded pea protein isolate (PPI) are investigated transversally to the fiber direction in the water content range between 40% w/w to 60% w/w. Young's modulus of elasticity in the transversal direction was found to decrease linearly with the water content from 2.6 MPa at a water content of 40% w/w to 0.6 MPa at the water content of 60% w/w at T = 21 ± 1 °C. Matrices extruded at different water contents of which the water content was adjusted to 60 ± 1% w/w showed decreasing values of Young's modulus. This variation in the transversal Young's modulus correlates linearly with the specific mechanical energy, confirming the impact of processing on the development of the protein network. The kinetics of aging of the extruded PPI matrices at T = 4 °C were fitted using an exponential equation and were observed to be dependent on the water content. Characteristic aging rates varied from an aging rate of ∼0.1 h−1 for the matrices extruded at a water content of 40% w/w to ∼0.015 h−1 for the matrices extruded at a water content of 60% w/w. The degree of aging was found to be 43.2 ± 7.5%, independent of the protein content of the matrices. The current study is the first systematic investigation of the elastic properties of extruded plant protein matrices in the concentration range that is relevant for meat analogs and may serve in process optimization and product development as well as for fundamental studies into the properties of concentrated protein networks.

Characteristics estimation of natural fibre reinforced plastic composites using deep multi-layer perceptron (MLP) technique

Polymer Matrix Composite (PMC/Plastic Composite) often referred to as Plastic Composite with Natural fibre reinforcement has a huge interest in industries to manufacture components for various applications including medical, transportation, sports equipment etc. In the universe, different types of natural fibres are available which can be used for the reinforcement in PMC/Plastic Composite. So, the selection of appropriate fibre for the PMC/Plastic Composite/Plastic composite is a challenging task, but it can be done using an effective metaheuristic or optimization techniques. But in this type of optimal reinforcement fibre or matrix material selection, the optimization is formulated based on any one of the parameters of the composition. Hence to analyse the various parameter of any PMC/Plastic Composite/Plastic Composite without real manufacturing, a machine learning technique is recommended. The conventional simple or single-layer machine learning techniques were not sufficient to emulate the exact real-time performance of the PMC/Plastic Composite. Thus, a deep multi-layer perceptron (Deep MLP) algorithm is proposed to analyse the various parameter of PMC/Plastic Composite with natural fibre reinforcement. In the proposed technique the MLP is modified by including around 50 hidden layers to enhance its performance. In every hidden layer, the basis function is evaluated and subsequently, the sigmodal function-based activation is calculated. The proposed Deep MLP is utilized to evaluate the various parameters of PMC/Plastic Composite Tensile Strength, Tensile Modulus, Flexural Yield Strength, Flexural Yield Modulus, Young's Modulus, Elastic Modulus and Density. Then the obtained parameter is compared with the actual value and the performance of the proposed Deep MLP is evaluated based on the accuracy, precision, and recall. The proposed Deep MLP attained 87.2%, 87.18%, and 87.22% of accuracy, precision, and recall. Ultimately the proposed system proves that the proposed Deep MLP can perform better for the prediction of various parameters of PMC/Plastic Composite with natural fibre reinforcement.

Comparison of Parameters for Assessment of Carotid Stiffness and Their Association with Carotid Atherosclerosis in Rural Australian Adults: A Pilot Study.

Carotid stiffness has been associated with the development and progression of carotid artery disease and is an independent factor for stroke and dementia. There has also been a lack of comparison of different ultrasound-derived carotid stiffness parameters and their association with carotid atherosclerosis. This pilot study aimed to investigate the associations between carotid stiffness parameters (derived via ultrasound echo tracking) and the presence of carotid plaques in Australian rural adults. In cross-sectional analyses, we assessed forty-six subjects (68 ± 9 years; mean ± SD) who underwent carotid ultrasound examinations. Carotid stiffness was assessed by a noninvasive echo-tracking method, measuring and comparing multiple carotid stiffness parameters, including stroke change in diameter (ΔD), stroke change in lumen area (ΔA), β- stiffness index, pulse wave velocity beta (PWV-β), compliance coefficient (CC), distensibility coefficient (DC), Young's elastic modulus (YEM), Peterson elastic modulus (Ep), and strain. Carotid atherosclerosis was assessed bilaterally by the presence of plaques in the common and internal carotid arteries, while carotid stiffness was assessed at the right common carotid artery. β-stiffness index, PWV-β, and Ep were significantly higher (p = 0.006, p = 0.004, p = 0.02, respectively), whilst ΔD, CC, DC, and strain were lower among subjects with carotid plaques (p = 0.036, p = 0.032, p = 0.01, p = 0.02, respectively) comparing to subjects without carotid plaques. YEM and ΔA did not significantly differ among the groups. Carotid plaques were associated with age, history of stroke, coronary artery disease, and previous coronary interventions. These results suggest that unilateral carotid stiffness is associated with the presence of carotid plaques.

Adipose-Derived Stem Cells in Reinforced Collagen Gel: A Comparison between Two Approaches to Differentiation towards Smooth Muscle Cells.

Scaffolds made of degradable polymers, such as collagen, polyesters or polysaccharides, are promising matrices for fabrication of bioartificial vascular grafts or patches. In this study, collagen isolated from porcine skin was processed into a gel, reinforced with collagen particles and with incorporated adipose tissue-derived stem cells (ASCs). The cell-material constructs were then incubated in a DMEM medium with 2% of FS (DMEM_part), with added polyvinylalcohol nanofibers (PVA_part sample), and for ASCs differentiation towards smooth muscle cells (SMCs), the medium was supplemented either with human platelet lysate released from PVA nanofibers (PVA_PL_part) or with TGF-β1 + BMP-4 (TGF + BMP_part). The constructs were further endothelialised with human umbilical vein endothelial cells (ECs). The immunofluorescence staining of alpha-actin and calponin, and von Willebrand factor, was performed. The proteins involved in cell differentiation, the extracellular matrix (ECM) proteins, and ECM remodelling proteins were evaluated by mass spectrometry on day 12 of culture. Mechanical properties of the gels with ASCs were measured via an unconfined compression test on day 5. Gels evinced limited planar shrinkage, but it was higher in endothelialised TGF + BMP_part gel. Both PVA_PL_part samples and TGF + BMP_part samples supported ASC growth and differentiation towards SMCs, but only PVA_PL_part supported homogeneous endothelialisation. Young modulus of elasticity increased in all samples compared to day 0, and PVA_PL_part gel evinced a slightly higher ratio of elastic energy. The results suggest that PVA_PL_part collagen construct has the highest potential to remodel into a functional vascular wall.

A prediction of Young's modulus for tin containing phosphate glasses using quantitative structural information

A rigid unit packing fraction (RUPF) model was used to better understand the influence of local structural units on the Young's elastic modulus (E) of binary and ternary tin phosphate glasses. Quantitative analyses of the units that constitute the glass structure, obtained from X-ray/neutron diffraction and 31P MAS-NMR spectroscopy, were used to calculate polyhedral packing fractions that, with tabulated bond dissociation energies, were used to predict E based on a modification of the Makashima-Mackenzie relationship, which uses ion sizes to calculate packing fractions. Predictions based on the RUPF model are better than those based on ion sizes, and extending the RUPF model to all cation-polyhedra accounts for the compositional dependence of the Sn-coordination number.

Modelling of the Torsional Simple Shear Test with Randomized Tresca Model Properties in Midas GTS NX

The dynamic properties of soil obtained from the torsional simple shear test (TOSS) are assumed to be uniform throughout the specimen. For some exceptional soils, this may hold true, but for the most majority of soils that we examine, it is obviously not the case, and this level of non-uniformity depends on the conditions in which the soil was formed. In this paper, we discuss a method of modelling inherently non-uniform soil specimens by representing them with elements that have an elasto-plastic simple Tresca material model with different properties (Elastic young modulus and yield stresses). The combination of properties that can simulate the nonlinear behaviour of the soil is found and calibrated using a model of the TOSS test built in the finite element software Midas GTS NX. Furthermore, the influence of rigid inclusions in the soil is studied and the results show an increase in stiffness with the increasing percentage of inclusion in the soil.

SURFACE PROPERTIES OF FLUOROCARBON COATINGS PRODUCED BY LOW-FREQUENCY PLASMATRON AT ATMOSPHERIC PRESSURE

This paper presents the results of studies conducted on coatings based on thin fluorocarbon films obtained by plasma-enhanced chemical vapor deposition using low-frequency plasmatron and low-temperature plasma at atmospheric pressure. The possibility of forming thin fluorocarbon layers by supplying a cyclohexane/carbon tetrafluoride gas mixture to substrates made of polymeric materials (polyethylene terephthalate and polystyrene) has been demonstrated and the main technological modes of deposition process have been established. The absorption spectra of the obtained coatings were studied, the influence of the gas discharge energy contribution on the concentration of fluorocarbon compounds was established, and the band gap was calculated using the Tauc method. The surface relief of the obtained structures was considered using atomic force microscopy and the root-mean-square deviation of the surface roughness was calculated, which reached a maximum of 36 ± 3 nm. Using the Oliver-Pharr method, the nanohardness and Young's modulus of elasticity of the obtained coatings were calculated, which amounted to 0.447 ± 0.025 and 6.10 ± 0.39 GPa, respectively.

Electrospun polycaprolactone nanofibers functionalized with Achillea millefolium extract yield biomaterial with antibacterial, antioxidant and improved mechanical properties.

In this study, polycaprolactone (PCL), as a biocompatible polymer was functionalized by addition of medicinal plant extract- Achillea millefolium L. (yarrow). Nanofiber mats were fabricated from PCL solutions containing dry yarrow extract in four concentrations (5%, 10%, 15%, and 20% relative to the weight of the polymer) by using blend electrospinning method. The nanofibers were characterized for their biological, mechanical and drug release behavior. In vitro release of yarrow polyphenols from the electrospun PCL nanofibers over a period of 5 days showed the release of up to 98% of the total loaded polyphenols. The released polyphenols retained its antioxidant activity, which was determined by DPPH assay. Electrospun PCL/yarrow nanofiber mats exhibited the antibacterial effect against Staphylococcus aureus, but had no effect on the growth of Pseudomonas aeruginosa. All PCL/yarrow nanofiber mats had improved mechanical properties compared to the neat PCL nanofibers, as evident by an increase in Young's modulus of elasticity (up to 5.7 times), the tensile strength (up to 5.5 times), and the strain at break (up to 1.45 times). Based on our results, yarrow-loaded PCL nanofiber mats appeared to be multi-functional biomaterials suitable for the production of catheter-coating materials, patches, or gauzes with antibacterial and antioxidant properties.

Association of statin therapy with progression of carotid arterial stiffness: the Multi-Ethnic Study of Atherosclerosis (MESA).

Arterial stiffness progresses with age and is a predictor of adverse cardiovascular disease events. Studies examining associations of statin therapy with arterial stiffness have yielded mixed results. Associations between the duration and intensity of statin therapy and arterial stiffness have not been studied in a prospective multiethnic cohort. MESA participants (n = 1242) with statin medication use data at each exam (1-5) and who had undergone B-mode carotid ultrasound at baseline and at Exam 5 after (mean ± [SD]) 9.4 ± 0.5 years were analyzed. Carotid arterial stiffness was measured using the distensibility coefficient (DC) and Young's elastic modulus (YEM). Linear regression models were used to evaluate associations between DC and YEM and statin treatment duration and intensity. At baseline, participants were 66.5 ± 8.1 years old, 41% female, 36% White, 30% African American, 14% Chinese American, and 20% Hispanic. The mean baseline low-density lipoprotein cholesterol (LDL-C) was 149.5 ± 14.5 mg/dL. After adjusting for age, sex, race/ethnicity, and CVD risk factors, the percent changes in DC and YEM were found to not be significantly different in individuals on statin therapy at any combination of visits (1-4) compared to participants never on statin therapy (all p > 0.32). There were also no differences in the percent change in DC and YEM based on statin therapy intensity by quartile (all p > 0.14) over the 10-year follow-up period. Based on the aforementioned results, statin therapy was not associated with changes in carotid artery stiffness over nearly a decade of follow-up regardless of therapy duration or intensity.

Composition–structure–property relationships of transparent Ca–Al–Si–O–N oxynitride glasses: The roles of nitrogen and aluminum

AbstractWe explore the formation and composition–structure–property correlations of transparent Ca–Al–Si–O–N glasses, which were prepared by a standard melt‐quenching technique using AlN as the nitrogen source and incorporating up to 8 at.% of N. Their measured physical properties of density, molar volume, compactness, refractive index, and hardness—along with the Young, shear, and bulk elastic moduli—depended roughly linearly on the N content. These effects are attributed primarily to the improved glass‐network cross‐linking from N compared to O, rather than the formation of higher‐coordination AlO5and AlO6groups, where27Al magic‐angle‐spinning nuclear magnetic resonance experimentation revealed that aluminum is predominately present in tetrahedral coordination as AlO4units. Yet, several physical properties, such as the refractive index along with the bulk, shear, and Young's elastic moduli, increase concomitantly with the Al content of the glass. We discuss the incompletely understood mechanical–property boosting role of Al as observed both herein and in previous reports on oxynitride glasses, moreover suggesting glass‐composition domains that are likely to offer optimal mechanical properties.

Hygro-thermal vibration of bidirectional functionally graded porous curved beams on variable elastic foundation using generalized finite element method

The aim of this paper is to present the hygro-thermal vibration behavior of bidirectional functionally graded porous (BDFGP) curved beams resting on two-layer elastic foundations (EF) using the generalized finite element method (GFEM). In which, one of these two layers is composed of Winkler springs with the variation of modulus, while the other is composed of shear springs with a fixed modulus. The enrichment is accomplished by constructing the enriched mathematical space using an enriched FE shape function. Moisture causes tensile stresses in the x-axis direction without affecting mechanical characteristics of the material, while temperature changes Young's modulus of elasticity and thermal expansion coefficients. The free vibration equation for the curved beam is developed that relied on the k-order shear deformation beam theory and Hamilton's principle. The correctness of the proposed model is evaluated by comparing obtained numerical results of the present work to the findings of credible publications in the literature. By considering the free vibration responses of the curved beam, the effects of parameters such as the grading power indexes, the porosity coefficient, the temperature and moisture change, the opening angle of the curved beam, stiffness of the EF, boundary conditions, and the thickness-to-length ratio are investigated.

ANALYSIS OF THE CORRELATIONAL RELATIONSHIP BETWEEN THE RESULTS OF ULTRASOUND ELASTOGRAPHY AND THE VALUES OF THE MEASURED DIFFUSION COEFFICIENT IN ASSESSING UTERINE AND ADNEXAL STRUCTURES IN REPRODUCTIVE AGE WOMEN

The purpose of the study. To study the correlational relationship between the results obtained by examining the uterus and ovaries in healthy women of reproductive age using shear wave ultrasound elastography with elastometry and magnetic resonance imaging (MRI) and assessment of the measured diffusion coefficient (MDC) of diffusion-weighted images (DWI). Materials and methods. The study group consisted of 45 healthy women of reproductive age (the average age was 32.9±3.1 years). All of them underwent ultrasound examination with the technology of two-dimensional shear wave elastography with elastometry (Aixplorer, Supersonic Imagine, France) according to the method developed and implemented by us. The MRI of uterine and ovarian structures was performed using the DWI protocol (Excelart Vantage Atlas magnetic resonance tomograph, Toshiba, Japan, 1.5 T), the myometrium and the uterine mucosa in the body and cervix, ovaries were evaluated. In the automatic mode, the MDC of unaltered structures in the uterine body and cervix and their appendages was calculated in the area of interest on ADC-maps. The degree of correlational relationship between the results of ultrasound elastography with elastometry and magnetic resonance tomography with an estimate of the measured diffusion coefficient was calculated. Results. Correlation analysis of the relationship between rigidity and the MDC of uterine and adnexal structures showed a direct inverse relationship between these values and a high degree of connection by Cheddock scale (p = 0.000000). At this, lesser MDC values (mm2 /s) of similar structures of the organs under study corresponded to large quantitative values of the Young's elasticity modulus (kPa) of all uterine and ovarian structures. Conclusion. The obtained data make it possible to optimize the diagnostic algorithm and to supplement the standard protocols for ultrasound and magnetic resonance imaging studies of gynecological organs using two-dimensional shear wave elastography with elastometry and magnetic resonance tomography with an assessment of the measured diffusion coefficient of diffusion-weighted images.

STUDY ON THE TIME-FREQUENCY CHARACTERISTICS AND PROPAGATION LAW OF ACOUSTIC EMISSION LONGITUDINAL WAVES IN WOOD GRAIN DIRECTION

To study the propagation law of acoustic emission (AE) longitudinal waves in wood, therelationship among wave velocity, standing wave fundamental frequency and Young's modulus of elasticity was studied, and the energy decay model of AE longitudinal waves along the grain direction was established. Firstly, the propagation velocity of the longitudinal wave was calculated using the time-difference method. Then, the relationship between the wave velocity and Young's modulus of elasticity was analyzed and the method of calculating thelongitudinal wave velocity using the fundamental frequency was proposed. Finally, using different levels' pulse strings as AE sources, the attenuation law of AE signal energy with distance was studied. The results show that the longitudinal wave velocity can be estimated more accurately by using the standing wave fundamental frequency. The influence of Poisson's ratio needs to be considered when calculating the Young's modulus of elasticity by using thelongitudinal wave velocity.

Biodegradable Films from Spray Dried Starch Inclusion Complexes with Bioactive Compounds—The Effect of Glycerol and pH

AbstractIn the present study, thermoplastic films are prepared using spray dried starch‐bioactive compound systems powders with different concentrations of glycerol (20% or 40%). The starch‐based films are produced by casting after dissolution under neutral (pH 7) or alkaline conditions (pH 12). Results reveal that elevated glycerol contents lead to increased moisture and hygroscopicity which is related to the availability of more ─OH groups. ANOVA shows that the glycerol concentration, the pH value, and the interactions of bioactive compounds with glycerol, bioactive compounds with pH, and glycerol with pH, influence significantly the mechanical properties of the thermoplastic starch films. Young's modulus of elasticity increases alongside with glycerol content, indicating improved flexibility of the films. Stress decreases with higher glycerol contents and lower pH while strain on the contrary, increases as the glycerol and pH increase in the films. Significant differences are also observed in water adsorption and water vapor transmission rate values. As expected, water adsorption increases with increasing relative humidity (RH) with the glycerol content positively affecting the water uptake by the films. Microscopic examination indicates the homogeneous distribution of the bioactive compounds in the matrix of the films.