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1.
Sci Total Environ ; : 174567, 2024 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-38981542

RESUMO

Coal spontaneous combustion (CSC) is disturbed by complex downhole conditions. However, current research by scholars mainly focuses on the impact of single conditional disturbances on CSC, which is difficult to comprehensively characterize the oxidation and spontaneous combustion characteristics of granular coal in a complex environment. For this reason, a temperature-programmed gas chromatographer (TP-GC) hyphenated instrument and a C600 high-precision microcalorimeter was used for analysis. The variation rules of derived gas and oxidizing thermodynamic parameters in the coal oxidizing and heating process under stress-heat-gas interaction were obtained. The intrinsic action mechanism of stress-heat-gas interaction to increase the risk of spontaneous combustion of granular coal is described. The results showed that as the level of air leakage (AL) rate increased, the concentration of derived gases in the coal sample showed a "˄"-shaped trend, and the heat release intensity and heat release varied in stages, both reaching their peak at a leakage rate of 150 mL/min. Under different stress conditions, the heat release intensity and heat release of coal also reach their maximum at 150 mL/min, indicating a higher risk of spontaneous combustion of coal at 150 mL/min. As the stress increases, the coal­oxygen reaction is inhibited, leading to a decrease in the concentration of derived gases and a reduction in the average heat release of the coal sample. This indicates that particulate coal is prone to spontaneous combustion when subjected to high air leakage rate and low stress conditions. The experimental results provide a theoretical basis for the prevention of CSC under complex conditions.

2.
Curr Res Food Sci ; 8: 100739, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38708103

RESUMO

Pumpkin seeds are rich in protein (24-36.5%). Some of them are consumed as nuts, while others are regarded as waste and used for feeding animals. Protein hydrolysates from pumpkin seeds possess some bioactive properties, such as anti-oxidant activity. In this work, various composite alginate hydrogels contain Aloe vera, CMC, and tragacanth have been employed to protect PSPH against degradation in simulated gastrointestinal digestion (SGI) and regulate its release rate. The encapsulation efficiency of PSPH in plain alginate and beads with Aloe vera, CMC, and tragacanth combinations was 71.63, 75.63, 85.07, and 80.4%, respectively. The release rate of the plain alginate beads was %30.23 in the SGF and %52.26 in the SIF, and decreased in the composite-based beads. The highest decreasing rate in the antioxidant activity during SGI was observed in free PSPH, and the decreasing rate slowed down in the alginate-based composites. The swelling rate in plain alginate was %-23.43 and %25.43 in the SGF and SIF, respectively, and increased in the composite-based beads. The FTIR spectra of hydrogels before and after loading with PSPH showed identical absorption patterns and were similar to each other. Based on the data for SEM, it was revealed that substituting other polymers in polymer combinations with alginates resulted in a porosity reduction of the beads and smoother and more uniform surfaces. Based on the results, the combination of polysacchared with alginate could protect and increase the applicability of PSPH as a functional component in the food industry.

3.
Materials (Basel) ; 17(10)2024 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-38793395

RESUMO

In engineering practice, layered rock masses often display obvious anisotropy while deforming and failing, and the failure mode directly impacts the engineering construction stability. In this study, the fracture failure load, fracture toughness, crack deflection angle, and failure mode of a layered rock mass under different fracture modes were analyzed by utilizing improved asymmetric semi-circular disc specimens. According to the constitutive model of transversely isotropic materials, the maximum tensile stress (MTS), maximum energy release rate (MERR), and maximum strain energy density (MSED) calculation formulas were modified, and the calculation formulas of the three prediction criteria under anisotropic materials were derived. The calculation results were compared with the experimental results. The results show that the fracture toughness and crack deflection angle were significantly affected by the weak bedding plane. As a result of applying the MTS criterion, the results are closer to the experimental results, providing a solid foundation for engineering deformation, failure, and fracture analyses.

4.
Polymers (Basel) ; 16(10)2024 May 17.
Artigo em Inglês | MEDLINE | ID: mdl-38794616

RESUMO

Efforts to tap into the broad antimicrobial, insecticidal, and antioxidant activities of essential oils (EOs) are limited due to their strong odor and susceptibility to light and oxidation. Encapsulation of EOs and subsequent drying overcome these limitations and extend their applications. This study characterized freeze-dried (lyophilized) emulsions of eugenol (EU) and thymol (TY) EOs, encapsulated by chemically unmodified cellulose, a sustainable and low-cost resource. High-resolution scanning electron microscopy showed successful lyophilization. While the observed "flake-like" structure of the powders differed significantly from that of the emulsified microcapsules, useful properties were retained. Fourier transform infrared spectroscopy confirmed the presence of EOs in their corresponding powders and thermo-gravimetric analysis demonstrated high encapsulation efficiency (87-88%), improved thermal stability and resistance to evaporation, and slow EO release rates in comparison to their free forms. The lightweight and low-cost cellulose encapsulation, together with the results showing retained properties of the dried powder, enable the use of EOs in applications requiring high temperatures, such as EO incorporation into polymer films, that can be used to protect agricultural crops from microbial infections.

5.
J Mech Behav Biomed Mater ; 155: 106577, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38759587

RESUMO

The present study simulates the fracture behavior of diabetic cortical bone with high levels of advanced glycation end-products (AGEs) under dynamic loading. We consider that the increased AGEs in diabetic cortical bone degrade the materials heterogeneity of cortical bone through a reduction in critical energy release rates of the microstructural features. To simulate the initiation and propagation of cracks, we implement a phase field fracture framework on 2D models of human tibia cortical microstructure. The simulations show that the mismatch between the fracture properties (e.g., critical energy release rate) of osteons and interstitial tissue due to high AGEs contents can change crack growth trajectories. The results show crack branching in the cortical microstructure under dynamic loading is affected by the mismatches related to AGEs. In addition, we observe cortical features such as osteons and cement lines can prevent multiple cracking under dynamic loading even with changing the mismatches due to high AGEs. Furthermore, under dynamic loading, some toughening mechanisms can be activated and deactivated with different AGEs contents. In conclusion, the current findings present that the combination of the loading type and materials heterogeneity of microstructural features can change the fracture response of diabetic cortical bone and its fragility.


Assuntos
Osso Cortical , Produtos Finais de Glicação Avançada , Suporte de Carga , Humanos , Osso Cortical/metabolismo , Produtos Finais de Glicação Avançada/metabolismo , Fenômenos Biomecânicos , Fraturas Ósseas/metabolismo , Tíbia/metabolismo , Análise de Elementos Finitos , Estresse Mecânico
6.
Bioresour Technol ; 402: 130829, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38734261

RESUMO

Most marine microalgae are typically cultivated in coastal areas due to challenges in inland cultivation. In this 185 days experiment, Nannochloropsis oceanica was semi-continuously cultivated inland using different photobioreactors (PBRs). The newly designed 700-liter (L) PBR exhibited tolerance to seasonal changes compared to the 150-L PBRs. The innovative in-situ oxygen release rate (ORR) measurement method results indicated that ORR was influenced by light intensity and temperature. The optimal temperature range for N. oceanica growth was 14-25 â„ƒ, demonstrated cold tolerance and lipid accumulation at low temperatures. The maximum lipid content in 700-L and 150-L PBRs was 29 % and 28 %, respectively. Based on the average biomass productivity, the price of N. oceanica was $11.89 kg-1 (or $3.35 kg-1 based on maximum biomass productivity), which is cheaper than the current market price of $20.19 kg-1. From results, smaller PBRs at the same hydro electricity price are more cost-effective.


Assuntos
Biomassa , Microalgas , Fotobiorreatores , Estramenópilas , Microalgas/crescimento & desenvolvimento , Microalgas/metabolismo , Estramenópilas/crescimento & desenvolvimento , Estramenópilas/metabolismo , Temperatura , Oxigênio , Luz
7.
Animals (Basel) ; 14(7)2024 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-38612258

RESUMO

The 2019-2020 Australian bushfire season had a devastating impact on native wildlife. It was estimated that 3 billion native animals were impacted by the fires, yet there are few estimates of the number of animals that were rescued and rehabilitated post-fire. Focusing on the state of New South Wales (NSW) and Kangaroo Island, South Australia, we used a case study approach to determine the number of marsupials that were reported rescued due to the 2019-2020 bushfires in these areas and analysed species-specific trends in rescue and release success. In NSW, we found 889 reports of fire-affected marsupials in 2019-2020, mostly comprising kangaroos and wallabies (macropods; n = 458), koalas (n = 204), and possums (n = 162), with a smaller number of wombats (n = 43) and other marsupial species. Most reports of fire-affected marsupials occurred 6-8 weeks after fire ignition, and there was no difference in temporal frequency of rescues between marsupial groups. For the three main groups, the probability of survival and subsequent release differed, with macropods having the lowest probability of release after rescue (0.15 ± 0.04) compared to koalas (0.47 ± 0.04) and possums (0.55 ± 0.10). The type of injury was the main predictor of survival during rehabilitation for all three marsupial groups, with those malnourished/moribund or with traumatic injuries less likely to survive rehabilitation. Death or euthanasia occurred on the day of rescue for 77% of macropods, 48% of possums and 15% of koalas. Koalas most often died during rehabilitation rather than on the day of rescue, with 73% either dying or being euthanised between day 1 and 30 post-rescue, representing a potential welfare concern. On Kangaroo Island, koalas were the most frequently rescued marsupial species; most euthanasia cases and deaths occurred in a hospital, whereas other marsupials were mostly euthanised at triage. In both jurisdictions, koalas were over-represented while possums were under-represented relative to baseline population densities and wildlife rescue trends in the years before the 2019-2020 bushfires. These species differences in presentation post-fire warrant further investigation, as do the differences in triage, survival and release outcomes. It is hypothesised that the high intensity and large scale of the 2019-2020 fires impeded marsupial fire evasion tactics, as evidenced by the small number of animals found for rescue, and the differing rates of presentation relative to underlying population densities for the main marsupial groups. Based on our findings, there is a need for detailed record keeping and data sharing, development of consistent and evidence-based triage, treatment and euthanasia guidelines and deployment of trained wildlife emergency rescue teams with advanced search techniques to minimise animal suffering where safe to do so.

8.
Artigo em Inglês | MEDLINE | ID: mdl-38658479

RESUMO

Aortic dissection, a critical cardiovascular condition with life-threatening implications, is distinguished by the development of a tear and its propagation within the aortic wall. A thorough understanding of the initiation and progression of these tears, or cracks, is essential for accurate diagnosis and effective treatment. This paper undertakes a fracture mechanics approach to delve into the mechanics of tear propagation in aortic dissection. Our objective is to elucidate the impact of geometric and material parameters, providing valuable insights into the determinants of this pivotal cardiovascular event. Through our investigation, we have gained an understanding of how various parameters influence the energy release rate for tear propagation in both longitudinal and circumferential directions, aligning our findings with clinical data.

9.
Polymers (Basel) ; 16(7)2024 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-38611202

RESUMO

Curcumin is an antioxidant that can effectively eliminate free radicals. However, as its oral bioavailability is low, an effective delivery method is required. Phospholipid-based liposomes can encapsulate lipophilic drugs, such as curcumin, while liposome, cholesterol, and gum Arabic (GA) can enhance the internal and external stability of drug membranes. This present study used concentrations of cholesterol (Cchol) and GA (CGA), ranging from 0 to 10, 20, 30, and 40% as well as 0 to 5, 10, 15, 20, 30, and 40%, respectively, to encapsulate curcumin in a GA-cocoliposome (CCL/GA) matrix and test its efficacy in simulated intestinal fluid (SIF) and simulated gastric fluid (SGF). The absence of new characteristic peaks in the Fourier transform infrared (FTIR) spectra results indicate the presence of non-covalent interactions in the CCL/GA encapsulation. Furthermore, increasing the Cchol decreased the encapsulation efficiency (EE), loading capacity (LC), and antioxidant activity (IR) of the CCL/GA encapsulation but increased its release rate (RR). Conversely, increasing CGA increased its EE and IR but decreased its LC and RR. The two conditions applied confirmed this. Liposomal curcumin had the highest IR in SIF (84.081%) and the highest RR in SGF (0.657 ppm/day). Furthermore, liposomes loaded with 10% Cchol and 20% CGA performed best in SIF, while those loaded with 10% Cchol and 30% CGA performed best in SGF. Lastly, the CCL/GA performed better in SIF than SGF.

10.
Heliyon ; 10(8): e29669, 2024 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-38681570

RESUMO

Because of their high protein content, easy access and low cost, pumpkin seeds are a valuable raw material for the preparation of antioxidant protein hydrolysates. Micro-coating is an effective method to protect bioactive compounds against destruction. In order to strengthen the alginate hydrogel network loaded with pumpkin seed protein hydrolysate (PSPH), CMC was added as part of its formulation in the first step, and chitosan coating was used in the second step. Then, swelling amount, release in the simulated gastrointestinal environment (SGI), antioxidant activity after SGI, Fourier transform infrared spectroscopy (FTIR), zeta potential, dynamic light scattering (DLS), polydispersity index (PDI) and scanning electron microscopy (SEM) of the samples were evaluated. The results showed that, the swelling amount of the chitosan-alginate hydrogel was lower than the chitosan-alginate-CMC sample, and with the increase in chitosan concentration, the swelling amount decreased. The release amount in the chitosan-alginate sample was higher than that in the chitosan-alginate-CMC sample, and with the increase in chitosan concentration, the release rate decreased. Also, the amount of release increased with the passage of time. The highest antioxidant activity belonged to the chitosan-alginate sample in SGI, and it increased with increasing the chitosan concentration. All findings demonstrated that the use of multi-component hybrid systems is a useful method for the protection of bioactive compounds against destruction, their antioxidant activities and their release behavior.

11.
Sci Rep ; 14(1): 7993, 2024 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-38580708

RESUMO

The current work aimed to improve the combustion behavior of a non-premixed twin-jet inlet. The effect of fuel and air inlet shape under different velocities was studied using ANSYS as the process takes place in species transport and finite rate/eddy dissipation, and the flow is considered to be turbulent. Two different shapes (circular-circular and circular-elliptic inlet jets) were investigated, and the results show that the behavior and intensity of the fire are affected by variations in the speed and, geometry of the inlet which affects temperature, heat release rate, combustion efficiency, and equivalent ratios. The optimum air/fuel velocities were found to be 2.5/1.5 with circular-circular inlet jets.

12.
Comput Methods Programs Biomed ; 247: 108102, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38447317

RESUMO

BACKGROUND AND OBJECTIVE: The effectiveness of current microwave ablation (MWA) therapies is limited. Administration of thermosensitive liposomes (TSLs) which release drugs in response to heat has presented a significant potential for enhancing the efficacy of thermal ablation treatment, and the benefits of targeted drug delivery. However, a complete knowledge of the mechanobiological processes underlying the drug release process, especially the intravascular drug release mechanism and its distribution in response to MWA needs to be improved. Multiscale computational-based modeling frameworks, integrating different biophysical phenomena, have recently emerged as promising tools to decipher the mechanobiological events in combo therapies. The present study aims to develop a novel multiscale computational model of TSLs delivery following MWA implantation. METHODS: Due to the complex interplay between the heating procedure and the drug concentration maps, a computational model is developed to determine the intravascular release of doxorubicin from TSL, its transvascular transport into the interstitium, transport in the interstitium, and cell uptake. Computational models can estimate the interplays among liposome and drug properties, tumor perfusion, and heating regimen to examine the impact of essential parameters and to optimize a targeted drug delivery platform. RESULTS: Results indicated that the synergy of TSLs with MWA allows more localized drug delivery with lower side effects. The drug release rate and tumor permeability play crucial roles in the efficacy of TSLs during MWA treatment. The computational model predicted an unencapsulated drug lime around the ablated zone, which can destroy more cancer cells compared to MWA alone by 40%. Administration of TSLs with a high release rate capacity can improve the percentage of killed cancer cells by 24%. Since the heating duration in MWA is less than 15 min, the presented combination therapy showed better performance for highly permeable tumors. CONCLUSION: This study highlights the potential of the proposed computational framework to address complex and realistic scenarios in cancer treatment, which can serve as the future research foundation, including advancements in nanomedicine and optimizing the pair of TSL and MWA for both preclinical and clinical studies. The present model could be as a valuable tool for patient-specific calibration of essential parameters.


Assuntos
Micro-Ondas , Neoplasias , Humanos , Micro-Ondas/uso terapêutico , Sistemas de Liberação de Medicamentos/métodos , Lipossomos/uso terapêutico , Doxorrubicina , Neoplasias/tratamento farmacológico
13.
Fire Mater ; 48(2)2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38525471

RESUMO

Exhaust flow measurements are a significant source of uncertainty for measurements of heat release rate in large-scale fire experiments. Irregular flow distributions are often present in the exhaust ducts making it difficult to measure flow accurately. Tracer gas dilution (TGD), a measurement method for volume flow, is not sensitive to flow distribution and has been applied to calibrate flow measurement devices at the exhaust ducts of a large-scale open calorimetry system. The in-line calibration reduced the bias in the exhaust flow measurement by as much as 6% improving the overall measurement accuracy of the heat release rate. Experimental results provide evidence that the flow calibration is an improvement over the accepted practice of developing a flow correction from the comparison of oxygen consumption calorimetry with the heat output from a gas burner. The flow calibration is valid for a wide range of flow conditions and decouples the oxygen consumption calorimetry measurement from any error in determining the heat release rate from the gas burner.

14.
Materials (Basel) ; 17(4)2024 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-38399130

RESUMO

Plant-derived selenium is an important source of selenium (Se) for humans, which, however, has been restricted by a low content of Se in soil. Traditional Se fertilizers have tended to result in low selenium utilization. Thus, it was necessary to develop a new slow-release material to control Se fertilizer release. In this study, biochar pyrolyzed at 300 °C and 800 °C was cross-linked with polyethyleneimine (PEI) after being treated with HNO3 or NaOH (which were labeled Acid-W300, Acid-W800, Alkali-W300, and Alkali-W800). The results showed that the maximum adsorption capacities of Acid-W300, Alkali-W300, Acid-W800, and Alkali-W800 were 329.16 mg/g, 321.93 mg/g, 315.04 mg/g, and 344.33 mg/g, respectively. Among them, Acid-W800 and Alkali-W800 were mainly imine- and amide-bonded with SO32-, while Acid-W300 and Alkali-W300 were loaded with SO32- by forming the C-Se bonding as well as through imine- and amide-bonding. The release of four biochar-based selenium fertilizers in the red soil and brown soil extracts conformed to the pseudo-second-order kinetic model. The release rate and release amount of four biochar-based selenium fertilizers in the red soil extract were higher than those in the brown soil extract. Alkali-W800-Se had a higher proportion of Se-exchangeable release, accounting for 87.5% of the total loaded selenium, while Acid-W300-Se had the lowest proportion at 62.2%. However, the Se releases of Alkali-W800-Se were more than 42.49% and 37.67% of the total Se-loading capacity during 5 days of continuous red soil extraction and brown soil extraction, respectively. Acid-W300-Se released less than 20% of the total Se-loading capacity. Thus, Acid-W300-Se was the recommended slow-release Se fertilizer in red soil and brown soil.

15.
J Hazard Mater ; 466: 133627, 2024 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-38301440

RESUMO

Aqueous film forming foam (AFFF)-impacted asphalt and concrete may serve as potential secondary sources of per- and polyfluoroalkyl substances (PFAS) to the environment through surficial leaching. We aimed to understand the vertical distribution and surficial release of PFAS from AFFF-impacted asphalt and concrete cores collected from various locations (∼10-70 m distance between samples). Among the PFAS analyzed, 6:2 FTS was observed as having the highest concentration in the surface layer (0 - 0.5 cm) of concrete (225 µg kg-1) and in the runoff from the concrete (2600 ng L-1). PFOS was detected at the highest concentration in the surface layer (0 - 0.5 cm) of asphalt (47 µg kg-1) and associated runoff (780 ng L-1). The total mass of PFAS released during three rainfall simulations accounts for a fraction of the total mass in the surface layer (0 - 0.5 cm), ranging from 0.10 - 9.8% and 0.078 - 2.4% for asphalt and concrete cores, respectively. Asphalt exhibited a higher release rate than concrete, demonstrated by the higher total release coefficient of PFAS (4 - 16 m-2) compared to that of concrete cores (1 - 5 m-2). These results suggested that, similar to concrete, AFFF-impacted asphalt may be a secondary source of PFAS to the environment.

16.
Int J Solids Struct ; 286-2872024 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-38130319

RESUMO

Fibrous gels such as cartilage, blood clots, and carbon-nanotube-based sponges with absorbed oils suffer a reduction in volume by the expulsion of liquid under uniaxial tension, and this directly affects crack-tip fields and energy release rates. A continuum model is formulated for isotropic fibrous gels that exhibit a range of behaviors from volume increasing to volume decreasing in uniaxial tension by changing the ratio of two material parameters. The motion of liquid in the pores of such gels is modeled using poroelasticity. The direction of liquid fluxes around cracks is shown to depend on whether the gel locally increases or decreases in volume. The energy release rate for cracks is computed using a surface-independent integral and it is shown to have two contributions - one from the stresses in the solid network, and another from the flow of liquid. The contribution to the integral from liquid permeation tends to be negative when the gel exhibits volume decrease, which effectively is a crack shielding mechanism.

17.
Front Bioeng Biotechnol ; 11: 1283293, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37929200

RESUMO

Introduction: When an intraocular lens (IOL) injector is inserted through a pre-cut corneal incision (e.g., an empirical size of 2.2 mm) during small incision cataract surgery, uncontrollable tearing to the corneal tissue may occur, which is highly associated with the incision shape, size, and location. The goal of this numerical study was to investigate the optimal incision scheme amongst three typical shapes, i.e., straight, frown, and chevron incisions using mechanical modeling and finite element analysis. Methods: Assuming that the damage is caused by the tissue fracture at the incision tips and is governed by the classical energy release rate (ERR) theory which compares the current ERR value subject to IOL injection and the material's intrinsic parameter, critical ERR G c. Results: It was found that for chevron incisions, the incision shape with an angle of 170° was superior which induced minimal ERR value, while for frown incisions, the shape with a central angle of 6° was optimal. Both chevron and frown incisions could allow a larger size of injector to inject through than a straight pre-cut. In particular, the frown incision performed the best due to its lowest corresponding ERR and easy operation. Discussion: It was also observed that regions where the embedded fibrils are more dispersed and exhibit high isotropy were more favorable. If necessary, the chevron incision was recommended to be more aligned with the direction exhibiting a larger modulus, for example, along the circumferential direction near the limbus. This study provides useful knowledge in operation design and a deep insight into mechanical damage to corneal wounds in small incision cataract surgery.

18.
Philos Trans A Math Phys Eng Sci ; 381(2263): 20230232, 2023 Dec 25.
Artigo em Inglês | MEDLINE | ID: mdl-37926205

RESUMO

In a seminal paper in the Philosophical Transactions of the Royal Society (A244, 87-112). Eshelby (Eshelby 1951 Phil. Trans. R. Soc. Lond. A 244, 87-112. (doi:10.1098/rsta.1951.0016)) introduced the concept of 'the force on an elastic singularity' and suggested that the extensions to dynamics include the application of the momentum flux. In this direction, it is shown that, in the non-uniformly motion of a dislocation there is a loss in quasi-momentum (or pseudo-momentum) across the scales ε to ε2, which induces an effective mass of the dislocation, and a loss in kinetic energy across the scales. It is shown through Noether's theorem that the rate of change of quasi-momentum in the volume enclosing the dislocation is equal to the flux of it through the surface minus a quasi-force, which is the dynamic J integral. The connection between the variation in the Hamiltonian and in the Lagrangian relates the quasi-force to the energy-release rate, yielding the same effective mass, while providing physical meaning both through momentum and energy. The effective mass of a dislocation is important in relating the energetics of defects from the micro to the macro scales, and the loss of quasi-momentum can have wider applications in continua. This article is part of the theme issue 'Foundational issues, analysis and geometry in continuum mechanics'.

19.
Comput Methods Programs Biomed ; 242: 107873, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37863011

RESUMO

BACKGROUND AND OBJECTIVE: Critical energy release rate is a global fracture parameter that could be measured during the failing process, and its value may change under different failure conditions even in the same bone structure. The aim of this study was to propose an approach that combined the experimental test and finite element analysis to predict the critical energy release rates in the femoral cortical bone structures under compression and three-point bending loads. METHODS: Three-point bending and compression experiments and the corresponding fracture simulations were performed on the rat femoral cortical bone structures. Different values of energy release rate were repeatedly assigned to the finite element models to perform fracture simulations, and then the load-displacement curves predicted in each simulation were compared with the experimental data to back-calculate the critical energy release rate. RESULTS: The predicted data were similar to the experimental results when the calibrated energy release rate was suitable. The results showed that the cortical bone structure occurred shear open failure under compression load, and the predicted critical energy release rate was 0.12 N/mm. The same cortical bone structure occurred tensile open failure under three-point bending load, and the predicted critical energy release rate was 0.16 N/mm. CONCLUSIONS: The critical energy release rates were different under various failure conditions in one cortical bone structure. A comprehensive analysis from the perspectives of material mechanical properties, failure mode, and damage fracture mechanism was conducted to reveal the reasons for the differences in the critical energy release rate in the cortical bone structure, which provided a theoretical basis for the measurement of the critical energy release rate and the accurate fracture simulation.


Assuntos
Osso Cortical , Fraturas Ósseas , Animais , Ratos , Estresse Mecânico , Fêmur , Análise de Elementos Finitos
20.
Polymers (Basel) ; 15(17)2023 Sep 02.
Artigo em Inglês | MEDLINE | ID: mdl-37688261

RESUMO

The increased demand for cladding in high-rise buildings has prompted engineers to explore alternative products utilizing recycled materials. However, ensuring fire compliance in these alternative claddings, which are predominantly composed of low-volume polymer-based composites, poses a critical challenge. Traditional experimental methods for fire evaluation are costly, time consuming, and environmentally impactful. Considering this, a numerical approach was proposed for evaluating the fire performance of glass-polymer composite materials, which contain a high proportion of recycled glass and a lower percentage of rigid polyurethane. A cone calorimeter test was simulated using Computational Fluid Dynamics (CFD) software to investigate the flammability of the novel glass-polymer composite material. This validated numerical model was employed to assess the combustibility of the glass-polyurethane composite materials and identify influential parameters using the Design of Experiments (DoE) method. Statistical analysis revealed that three material properties, namely, the heat of combustion, the absorption coefficient, and the heat of reaction, significantly influenced the peak heat release rate (pHRR) of the glass-polyurethane composite materials compared to other properties. Based on these findings, an empirical equation was proposed that demonstrates a reasonable correlation with the pHRR of low-polymer recycled glass composite materials. The outcomes of this study hold considerable importance for understanding and predicting the combustibility behaviour of low-polymer-glass composites. By providing a validated numerical model and identifying critical material properties, this research contributes to the development of sustainable fire safety solutions for buildings, enabling the use of recycled materials and reducing reliance on conventional claddings.

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