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1.
Sci Rep ; 13(1): 1186, 2023 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-36681752

RESUMO

Rocks deformed at low confining pressure are brittle, which means that after peak stress, the strength declines to a residual value established by sliding friction. The stress drop is the variation between peak and residual values. But no tension reduction takes place at high confining pressure. A proposed definition of the brittle-ductile transition is the transition pressure at which no loss in strength takes place. However, studies that consider information about the brittle-ductile transition, the criterion's range of applicability, how to determine mi, and how confining pressures affect mi's values are scarce. This paper aims to investigate the link between brittle-ductile transition stress, uniaxial compressive strength and Hoek-Brown material constant (mi) for different kinds of rock. It is essential to accurately determine the brittle-ductile transition stress to derive reliable values for mi. To achieve this purpose, a large amount of data from the literature was chosen, regression analysis was carried out, and brittle-ductile transition stress (σTR) was determined based on the combination of Hoek-Brown failure criteria and the recently used brittle-ductile transition stress limit of Mogi. Moreover, new nonlinear correlations were established between uniaxial compressive strength and Hoek-Brown material constant (mi) for different igneous, sedimentary and metamorphic rock types. Regression analyses show that the determination coefficient between σTR and UCS for gneiss is 0.9, sandstone is 0.8, and shale is 0.74. Similarly, the determination coefficient between σTR and mi for gneiss is 0.88. The correlation between Hoek-Brown material constant (mi) and σTR was not notable for sedimentary and metamorphic rocks, probably due to sedimentary rocks' stratification and metamorphic ones' foliation.


Assuntos
Força Compressiva , Fricção , Resistência à Tração
2.
J Mech Behav Biomed Mater ; 138: 105611, 2023 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-36563457

RESUMO

Hydroxyapatite-reinforced Poly Lactic Acid (PLA) thermoplastic composite is mainly used for scaffolding and bone implant applications. They are developed using the naturally derived hydroxyapatite particles from marine industry waste, which proves to be economical and has ecological benefits towards the composite development. The mechanical and dimensional stability of the 3D printed composite can be varied based on the mineralogical and structural characteristics of the added particle reinforcement into the matrix. The present work concentrates on developing thin-walled PLA/hydroxyapatite composite tubes using fused filament fabrication technology by the novel extruded PLA/hydroxyapatite composite filament. For the current study, the hydroxyapatite particles are derived from crab shell waste, and the tube was fabricated with a wall thickness of 4 mm. In this work, the prepared composite tube's crashworthiness behavior and dimensional stability are studied concerning various experimental parameters such as build orientation, line width, printing speed, nozzle temperature, and layer height. The experimental parameters were optimized using the Taguchi optimization technique. The results showed that the optimized parameters for the maximum compressive strength would be a build orientation of 90°, a lower layer height of 0.1 mm, a nominal printing speed of 20 mm/s, a moderate nozzle temperature of 220 °C, and a line width of 0.2 mm. The rank of influential experimental parameters for the output response, such as compressive strength, was nozzle temperature > build orientation > layer height > line width > printing speed. Macroscopic observation of the failure samples shows that 90° oriented composites are subjected to compressive loading, and the progressive mode of fracture takes place, leading to the crushing of composites. This progressive fracture mode develops the highest compressive strength compared to other fracture modes and build orientations.


Assuntos
Citoesqueleto , Fraturas Ósseas , Humanos , Força Compressiva , Durapatita , Poliésteres
3.
Sci Rep ; 12(1): 20969, 2022 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-36470991

RESUMO

In engineering practices, it is critical and necessary to either measure or estimate the uniaxial compressive strength (UCS) of the rock. Measuring the UCS of rocks requires comprehensive studies in the field and in the laboratory for the rock block sampling, coring, and testing. These studies are time-consuming, expensive and go through difficult processes. Alternatively, the UCS can either be estimated by empirical relationships or predictive models with various measured mechanical and physical parameters of the rocks. Previous studies used different methods to predict UCS, including least squares regression techniques (MLR), adaptive neuro-fuzzy inference system (ANFIS), Sequential artificial neuron networks (SANN), etc. This study is intended to estimate the UCS of the carbonate rock by using a simple, measured Schmidt Hammer (SHVC) test on core sample and a unit weight (γn) of carbonate rock. Principal components regression (PCR), MLR, SANN, and ANFIS are employed to predict the UCS. We are not aware of any study compared the performances of these methods for the prediction of the UCS values. Based on the root mean square error, mean absolute error and R2, the Sequential artificial neural network has a slight advantage against the other three models.


Assuntos
Lógica Fuzzy , Aprendizado de Máquina , Modelos Lineares , Força Compressiva , Análise dos Mínimos Quadrados , Carbonatos
4.
PLoS One ; 17(12): e0279293, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36574382

RESUMO

Every year, a large amount of solid waste such as fly ash and slag is generated worldwide. If these solid wastes are used in concrete mixes to make concrete, it can effectively save resources and protect the environment. The compressive strength of concrete is an essential indicator for testing its quality, and its prediction is affected by many factors. It is difficult to predict its strength accurately. Therefore, based on the current popular machine learning supervised learning algorithms: Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVR), three models established a nonlinear mapping between multi-factor features and target feature concrete compressive strength. Using the three completed training models, we validated the test set with 206 example sets, and the Root Mean Square Error (RMSE), fitting coefficient (R2), and Mean Absolute Error (MAE) were used as evaluation metrics. The validation results showed that the values of RMSE, R2, and MAE for the RF model were 0.1, 0.9, and 0.21, respectively; the values of XGBoost model were 0.05, 0.95, and 0.15, respectively. The values of SVR were 0.15, 0.86, and 0.3, respectively. As a result, Extreme Gradient Boosting (XGBoost) has better generalization ability and prediction accuracy than the other two algorithms.


Assuntos
Algoritmos , Cinza de Carvão , Força Compressiva , Benchmarking , Aprendizado de Máquina , Resíduos Sólidos
5.
Molecules ; 27(23)2022 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-36500710

RESUMO

Slaker grits (SG) and biomass fly ash (BFA), two waste streams generated in the pulp and paper industry, are commonly disposed of in landfills, a practice with a high economic and environmental burden. In this work, their individual valorization as fillers in a commercial screed mortar formulation was evaluated in order to achieve a more sustainable management practice. The waste streams were characterized in terms of true density, particle size and morphology, and chemical and mineralogical composition. The influence of their incorporation amount (5.0, 7.5, and 10.0 wt.% of the total solids) and pre-treatment (sieving and grinding) on the fresh (workability) and hardened state (density, water absorption by capillarity, and flexural and compressive strength) properties of the mortars were assessed. The results show that the addition of 10.0 wt.% of the SG after milling and sieving (<75 µm) and 7.5 wt.% of BFA in the as-received condition, or up to 10.0 wt.% after grinding and sieving (<63 µm), allowed for the production of mortar samples with properties within the recommended specifications and that were resistant to 25 consecutive freeze-thaw cycles. This waste valorization route could represent an economic benefit of up to 8.85 €/tmortar and 2.87 €/tmortar for mortar, and pulp and paper companies, respectively.


Assuntos
Cinza de Carvão , Materiais de Construção , Cinza de Carvão/química , Biomassa , Tamanho da Partícula , Força Compressiva
6.
Rev. int. med. cienc. act. fis. deporte ; 22(88): 863-875, dic. 2022. tab
Artigo em Espanhol | IBECS | ID: ibc-213729

RESUMO

El objetivo de este trabajo es evaluar en 36 corredores aficionados, la fuerza y las presiones del pie sobre tres superficies comúnmente empleadas para el entrenamiento de la carrera en el sitio (césped artificial, suelo técnico de caucho y trampolín plano). Los valores de fuerza y presión se registraron mediante plantillas instrumentadas (Gebiomized® Munster, Germany). Se obtuvieron los siguientes parámetros: Fuerza máxima (N) y picos de presión (N/cm2) en 6 zonas específicas del pie. Según los resultados, la fuerza máxima ejercida por el pie dominante en césped artificial (657 N) y en suelo técnico de caucho (692,5 N) fue significativamente superior al registrado sobre el trampolín (262 N). Respecto a la presión, la mayor parte de la presión ejercida por el pie en superficies duras (césped artificial y suelo técnico de caucho), se observó en las cabezas de los metatarsianos, mientras que en el trampolín la presión se repartió entre estas y el calcáneo. (AU)


The objective of this study is to evaluate the Maximum Force and Peak Pressure of the foot on three surfaces commonly used for running in place training (artificial turf, rubber floor and flat trampoline). Force and pressure were recorded in 36 amateur runners using instrumented insoles (Gebiomized® Munster, Germany). The following parameters were obtained: Maximum Force (N) and Peak Pressure (N/cm2) in 6 specific areas of the foot. According to the results, the maximum force exerted by the dominant foot on artificial turf (657 N) and rubber floor (692.5 N) was significantly higher than the recorded on the trampoline (262 N). Regarding the pressure, most of the pressure exerted by the foot on hard surfaces (artificial turf and technical floor), was observed in the heads of the metatarsals, while in the trampoline the pressure was distributed in the heads of the metatarsals and the calcaneus. (AU)


Assuntos
Humanos , Masculino , Feminino , Adulto , Pessoa de Meia-Idade , Corrida , , Força Compressiva , Fenômenos Biomecânicos , Entrevistas como Assunto
7.
Sci Rep ; 12(1): 21547, 2022 12 13.
Artigo em Inglês | MEDLINE | ID: mdl-36513740

RESUMO

Researchers have made headway against challenges of increasing cement infrastructure and low plastic recycling rates by using waste plastic in cementitious materials. Past studies indicate that microbially induced calcium carbonate precipitation (MICP) to coat plastic in calcium carbonate may improve the strength. The objective of this study was to increase the amount of clean and contaminated waste plastic that can be added to mortar and to assess whether MICP treatment enhances the strength. The performance of plastic-filled mortar was investigated at 5%, 10%, and 20% volume replacement for cement. Untreated, clean plastics at a 20% cement replacement produced compressive strengths acceptable for several applications. However, a coating of MICP on clean waste plastic did not improve the strengths. At 10% replacement, both MICP treatment and washing of contaminated plastics recovered compressive strengths by approximately 28%, relative to mortar containing oil-coated plastics. By incorporating greater volumes of waste plastics into mortar, the sustainability of cementitious composites has the potential of being improved by the dual mechanisms of reduced cement production and repurposing plastic waste.


Assuntos
Materiais de Construção , Plásticos , Força Compressiva , Biomineralização , Carbonato de Cálcio
8.
PLoS One ; 17(12): e0278782, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36516167

RESUMO

Rockburst physical model test, as one of the important means to study deep tunnel engineering, reflects the main influencing factors of rockburst into the model test through similar theory, so as to reveal the formation mechanism, influencing factors and evolution law of different types of rockburst in deep tunnels. In order to study the mechanical properties of white sandstone in deeply buried tunnels at high ground temperatures, materials suitable for conducting rockburst physical and mechanical tests were developed on the basis of the Daqian Shi Ling tunnel project, and similar material ratios were preferentially selected on the basis of white sandstone. Judged by the rock burst propensity, similar materials with low strength and high brittle characteristics, can better simulate the characteristics of white sandstone, and all show a strong propensity to rock burst, is the ideal rock burst similar materials. Uniaxial compressive tests were conducted on similar materials and the original rock at different temperatures, and comparative analysis was performed. Through the study of stress, displacement and modulus of elasticity, it was concluded that the compressive strength of similar materials gradually increased with temperature in the range of 20-100°C, and the vertical displacement at peak strength decreased with increasing temperature. The damage forms of white sandstone and similar materials at different temperatures were comparatively analyzed, and it was obtained that the damage forms of white sandstone and similar materials were basically the same, with a few specimens showing tensile and shear damage, and most specimens showing the form of combined tensile and shear damage. The study of rock burst similar materials and the development of the failure characteristics of rock burst under the action of thermal coupling are of great significance to the mechanism of rock burst generation and prediction.


Assuntos
Engenharia , Gastrópodes , Animais , Temperatura , Força Compressiva , Elasticidade
9.
PLoS One ; 17(12): e0278161, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36548370

RESUMO

The estimation of concrete characteristics through artificial intelligence techniques is come out to be an effective way in the construction sector in terms of time and cost conservation. The manufacturing of Ultra-High-Performance Concrete (UHPC) is based on combining numerous ingredients, resulting in a very complex composite in fresh and hardened form. The more ingredients, along with more possible combinations, properties and relative mix proportioning, results in difficult prediction of UHPC behavior. The main aim of this research is the development of Machine Learning (ML) models to predict UHPC flowability and compressive strength. Accordingly, sophisticated and effective artificial intelligence approaches are employed in the current study. For this purpose, an individual ML model named Decision Tree (DT) and ensembled ML algorithms called Bootstrap Aggregating (BA) and Gradient Boosting (GB) are applied. Statistical analyses like; Determination Coefficient (R2), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE) are also employed to evaluate algorithms' performance. It is concluded that the GB approach appropriately forecasts the UHPC flowability and compressive strength. The higher R2 value, i.e., 0.94 and 0.95 for compressive and flowability, respectively, of the DT technique and lesser error values, have higher precision than other considered algorithms with lower R2 values. SHAP analysis reveals that limestone powder content and curing time have the highest SHAP values for UHPC flowability and compressive strength, respectively. The outcomes of this research study would benefit the scholars of the construction industry to quickly and effectively determine the flowability and compressive strength of UHPC.


Assuntos
Inteligência Artificial , Compressão de Dados , Força Compressiva , Algoritmos , Aprendizado de Máquina , Veículos Farmacêuticos
10.
Int J Mol Sci ; 23(24)2022 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-36555114

RESUMO

Foam concrete is widely used for its excellent properties, such as light weight, heat insulation, fire resistance, and sound insulation. The stability of foam is the main factor that affects the mechanical performance of foam concrete. The experiments are designed from two perspectives: the foam's stability performance and the foam concrete's modification effect. The effects on foam volume, foam half-life, foam bleeding rate, and foam pore size were investigated based on different concentrations of foam stabilizer CMC (0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%). A combination of macroscopic testing and microscopic analysis, a comparative study of dry density, water absorption test, mechanical property test, and pore structure analysis were conducted after using the modified foam for foam concrete. It is shown that the addition of CMC has an enhanced effect on foam stability. Foaming volume, water secretion rate, and average pore size showed a decreasing trend with the increase of CMC admixture, while the foam half-life displayed an increasing trend. In addition, adding CMC reduces the dry density and improves water absorption and compressive strength. The pore structure development of foam concrete has a noticeable improvement effect, and the optimal amount of admixture is 0.4%. Research results provide a reference for applying thickening foam stabilizer CMC in foam concrete.


Assuntos
Carboximetilcelulose Sódica , Estro , Animais , Força Compressiva , Excipientes , Água
11.
ACS Appl Mater Interfaces ; 14(46): 51711-51727, 2022 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-36354323

RESUMO

PMMA bone cement has been clinically used for decades in vertebroplasty due to its high mechanical strength and satisfactory injectability. However, the interface between bone and PMMA is fragile and more prone to refracture in situ because PMMA lacks a proper biological response from the host bone with minimal bone integration and dense fibrous tissue formation. Here, we modified PMMA by incoporating borosilicate glass (BSG) with a dual glass network of [BO3] and [SiO4], which spontaneously modulates immunity and osteogenesis. In particular, the BSG modified PMMA bone cement (abbreviated as BSG/PMMA cement) provided an alkaline microenvironment that spontaneously balanced the activities between osteoclasts and osteoblasts. Furthermore, the trace elements released from the BSGs enhanced the osteogenesis to strengthen the interface between the host bone and the implant. This study shows the first clinical case after implantation of BSG/PMMA for three months using the dual-energy CT, which found apatite nucleation around PMMA instead of fibrous tissues, indicating the biological interface was formed. Therefore, BSG/PMMA is promising as a biomaterial in vertebroplasty, overcoming the drawback of PMMA by improving the biological response from the host bone.


Assuntos
Cimentos Ósseos , Vertebroplastia , Polimetil Metacrilato , Força Compressiva , Apatitas
12.
Sci Rep ; 12(1): 20565, 2022 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-36447015

RESUMO

The paper reviews the properties of cement composites reinforced with short fibres. The effect of natural fibres was investigated: cotton, sisal, jute, ramie, bamboo, and synthetic fibres: polymer and polypropylene. It was noticed that the fibres change the consistency of the mixture up to 15%. In the composite flexural strength tests, a change in strength by +/- 8% was observed, depending on the type of fibres used. The research shows that the use of natural fibres had a positive effect on the compressive strength by 27%, while the use of synthetic fibres caused its decrease by 4%. Additionally, it was noticed that the chemical composition, the diameter and the total length of the fibres in the element have an impact on the composite shrinkage. The fibre-containing composites showed an 8% higher water absorption compared to the non-fibre samples. The exception is the ramie fibres, which reduce water absorption. In general, a positive effect of natural fibers on the properties of cement composites has been noticed, however, in case of natural fibres application, a thorough further properties investigation is recommended.


Assuntos
Boehmeria , Cimentos de Ionômeros de Vidro , Materiais Dentários , Cimentos Ósseos , Resistência à Flexão , Força Compressiva
13.
Sci Rep ; 12(1): 17968, 2022 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-36289402

RESUMO

The comparative study of natural hydroxyapatite (NHAp) from bovine (B) and catfish (C) bones using different fabrication parameters has been extensively researched through traditional investigation. However, the quantitative effect optimization of a novel mix proportion of hydroxyapatite from these bones, and fabrication parameters have not been examined. Hence, this study presents the effect of the powder mixture, compaction pressure, and sintering temperature (as production parameters) on the experimental mechanical properties of naturally derived HAp. The bovine bone and catfish bone biowastes were used in mixed proportions to produce hydroxyapatite via the sol-gel synthesis protocol. The powders were calcined separately at 900 °C to convert the deproteinized biowaste. Next, the powders were combined chemically (sol-gel) in the appropriate ratios (i.e. 45 g of B: 15 g of C (B75/C25), 30 g of B: 30 g of C (B50/C50), and 15 g of B; 45 g of C (B25/C75)). Taguchi design supported by grey relational analysis was employed with an L9 orthogonal array. The Minitab 16 software was employed to analyze the Taguchi design. The result revealed an inconsistency in the powder mixture as the optimum state for individual mechanical properties, but the grey relational analysis (GRA) showed better mechanical properties with a powder mix of B50/C50, 500 Pa compaction pressure, and 900 °C sintering temperature. The obtained result further showed that the novel mix of these powders is a good and promising material for high-strength biomedical applications, having a contribution of 97.79% on hardness and 94.39% on compressive strength of HAp. The obtained experimental grey relational grade of 0.7958 is within the 95% confidence interval, according to confirmation analysis (CA). The optimum powder parameter was examined using X-ray diffraction (XRD), and its structure, size, and elemental makeup were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. The sample had a higher degree of crystallinity and mean crystallite size of 80.42% and 27.3 nm, respectively. The SEM images showed big, gritty grains that are not tightly packed.


Assuntos
Durapatita , Bovinos , Animais , Durapatita/química , Pós , Difração de Raios X , Microscopia Eletrônica de Varredura , Força Compressiva
14.
BMC Oral Health ; 22(1): 446, 2022 10 17.
Artigo em Inglês | MEDLINE | ID: mdl-36253744

RESUMO

BACKGROUND: Proper isolation and restoration of class V subgingival cavities are technique sensitive, thus the resin composite restoration is liable to contamination. This in vitro study was conducted to evaluate the surface microhardness and compressive strength of bulk-fill flowable resin composite after being contaminated during its packing. METHODS: Resin composite discs were prepared using split mold. The contaminated specimens were allocated into four groups (n = 20) according to the contaminant used: hemostatic agent (Group 1), alcohol (Group 2), artificial saliva (Group 3) and powdered gloves (Group 4). The non-contaminated specimens (n = 20) were used as control group. The surface microhardness and compressive strength of each group were tested 1-day post-photocuring (n = 5) and 1 month post-photocuring (n = 5). Values were presented as mean, standard deviation values and confidence intervals. RESULTS: The surface microhardness of all groups didn't show a significant difference for different tested groups except for alcohol which showed a significant reduction on surface microhardness compared to control at 1 day post-photocuring (p = 0.001). The highest compressive strength mean values at 1 day and 1 month post-photocuring were recorded in control groups (110.42 MPa and 172.87 MPa respectively), followed by alcohol groups, then hemostatic agent groups, followed by artificial saliva with the least value recorded in powdered gloves groups (56.71 MPa and 49.5 MPa respectively). CONCLUSIONS: Contamination of bulk-fill flowable resin composite with hemostatic agent, alcohol, artificial saliva, or powdered gloves during its packing decreased its compressive strength after 1 month post-photocuring rather than affecting its surface microhardness.


Assuntos
Resinas Compostas , Hemostáticos , Força Compressiva , Humanos , Teste de Materiais , Saliva Artificial
15.
PLoS One ; 17(10): e0275626, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36206282

RESUMO

To better understand the effect of the size of hole defects on the mechanical properties of a rock mass, the two-dimensional particle flow discrete element code (PFC2D) is applied to establish rock mass models with single circular hole defects of different diameters. Uniaxial compressive strength (UCS) tests are conducted on each model by only taking the defect size (area) as a variable. This study analyzes each model's stress-strain, contact force chain, crack evolution, meso-damage and failure, and mechanical properties. The results showed that with the size enlargement of the circular hole defects, each model's UCS and elastic modulus gradually decrease, and the defect size is negatively correlated with the mechanical strength of the rock samples. The size of the hole defects affects the entire process of contact force chain and crack evolution. The larger the aperture dimension of the circular hole defects in each model, the greater the concentration degree of the contact force chain, the earlier the crack initiation, and the higher the degree of crack coalescence in the post-peak stage. The number of cracks decreases as the hole size increases, and the model is more prone to failure. Rock models' strength and failure characteristics with different numbers and arrangements of hole defects are discussed under the same defect area condition.


Assuntos
Carbonato de Cálcio , Força Compressiva , Simulação por Computador , Módulo de Elasticidade , Estresse Mecânico
16.
Sensors (Basel) ; 22(19)2022 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-36236616

RESUMO

The topic of research included in this article was the evaluation of the influence of cenospheres on selected parameters of mortar cement. Samples were designed as CEM I 42.5 R Portland cement with the application of different additive amounts. In the experimental work, the consistency, compressive strength, and bending strength were tested after 28 and 56 days of maturation, and after heating temperatures of 20, 300, 500, and 700 °C. The compressive strength was tested on half beams (40 × 40 × 160 mm). Using the obtained results, the properties of the mortars were compared. The research confirmed the possibility of producing cenosphere-modified cement mortars. Cenospheres used in the preparation of cement mortar negatively affected the bending and compressive strength with increasing temperature (20, 300, 500, 700 °C) and increasing content of this additive (10, 20, 30%).


Assuntos
Materiais de Construção , Força Compressiva , Materiais de Construção/análise , Temperatura
17.
Med Eng Phys ; 108: 103882, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-36195367

RESUMO

Biomechanical CT (BCT), i.e., quantitative computed tomography-based finite element analysis (QCT-FEA), promises an improved technique over bone mineral density (BMD) in predicting bone strength and the risk of osteoporotic vertebral fractures. However, most of the BCT models only consider a uniform compressive loading condition and they have not been validated for Chinese subjects. This study examined the ability of BCT to predict wedge fracture-related vertebral flexion strength in a cohort of Chinese cadaveric vertebrae. Twelve human vertebrae were scanned with dual energy X-ray absorptiometry (DXA) and QCT to measure areal and volumetric BMD, respectively. To produce wedge fractures, the cadaveric vertebrae were experimentally loaded until failure under a 15° flexion. Vertebral flexion stiffness and strength were measured from the force-displacement curve. Voxel-based heterogeneous FE models of the vertebrae were created and virtually tested in uniform compression and 15° flexion to compute compressive and flexion strength (and stiffness), respectively. The predictions of vertebral flexion strength with BMD or BCT measures were evaluated with linear regression analyses. Results showed weak correlations between experimentally-measured flexion strength vs. DXA-aBMD (R2 = 0.26) or QCT-vBMD (R2 = 0.39). However, there were strong correlations between experimentally-measured flexion strength vs. BCT-computed vertebral strength under either flexion (R2 = 0.71) or compression (R2 = 0.70) loading conditions, although flexion reduced the BCT-computed vertebral strength by 9.2%. These results suggest that, regardless of whether a uniform compression or a flexion loading is simulated, BCT can predict in vitro vertebral flexion strength better than BMD.


Assuntos
Fraturas por Compressão , Fraturas por Osteoporose , Absorciometria de Fóton/métodos , Densidade Óssea , Cadáver , China , Força Compressiva , Análise de Elementos Finitos , Humanos , Vértebras Lombares , Testes Mecânicos , Coluna Vertebral , Tomografia Computadorizada por Raios X/métodos
18.
Int J Mol Sci ; 23(18)2022 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-36142380

RESUMO

Composites based on polylactide (PLA) and hydroxyapatite (HA) were prepared using a thermally induced phase separation method. In the experimental design, the PLA with low weight-average molar mass (Mw) and high Mw were tested with the inclusion of HA synthesized as whiskers or hexagonal rods. In addition, the structure of HA whiskers was doped with Zn, whereas hexagonal rods were mixed with Sr salt. The composites were sterilized and then incubated in phosphate-buffered saline for 12 weeks at 37 °C, followed by characterization of pore size distribution, molecular properties, density and mechanical strength. Results showed a substantial reduction of PLA Mw for both polymers due to the preparation of composites, their sterilization and incubation. The distribution of pore size effectively increased after the degradation process, whereas the sterilization, furthermore, had an impact on pore size distribution depending on HA added. The inclusion of HA reduced to some extent the degradation of PLA quantitatively in the weight loss in vitro compared to the control without HA. All produced materials showed no cytotoxicity when validated against L929 mouse skin fibroblasts and hFOB 1.19 human osteoblasts. The lack of cytotoxicity was accompanied by the immunocompatibility with human monocytic cells that were able to detect pyrogenic contaminants.


Assuntos
Durapatita , Poliésteres , Animais , Materiais Biocompatíveis/química , Força Compressiva , Durapatita/química , Humanos , Teste de Materiais , Camundongos , Poliésteres/química , Polímeros/química , Esterilização
19.
Sci Total Environ ; 852: 158516, 2022 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-36063952

RESUMO

Large volumes of carbon dioxide are released during mining and ore resource development, and cemented paste backfill (CPB) materials are placed in the mined-out stopes where can be discharged from polluted air containing CO2. The construction of green mines and the goal of achieving carbon neutrality have become an inevitable choice for the mining industry to achieve the harmonious development of rational exploitation of resources and environmental protection. Against this background, to minimize the carbon emissions from the mining industry and promote the efficient utilization of CPB, this study investigated the carbon-uptake characteristics and mechanical property of CPB in underground mined-out stopes with 1.5 % concentration CO2. The results show that the carbonation curing (CC) increased the carbonation rate by nearly 4 times compared to natural curing, while the samples exhibited total carbonation within 28 days. This indicates that CO2 uptake could occur within the CPB. The CO2 was absorbed as calcium carbonate minerals, and each ton of CPB can ideally absorb about 78.4 kg CO2 and treat 2600 m3 of dirty air in the mined-out stopes. The increase in early uniaxial compressive strength (UCS) during CC required a higher cement concentrate, and the CC would retard the development of later compressive strength. Microstructure analysis indicated that the CC refined the pore structure and reduced the porosity of the CPB. It also affected the crystal growth and distribution of hydration and carbonation products, further influencing the difference in strength. In summary, CPB technology can potentially be useful during carbon uptake and may assist in mitigating carbon emissions from the mining industry and promoting environment friendly development.


Assuntos
Dióxido de Carbono , Mineração , Força Compressiva , Carbonatos , Carbonato de Cálcio
20.
Comput Intell Neurosci ; 2022: 9541115, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35958762

RESUMO

Most building structures that are built today are built from concrete, owing to its various favorable properties. Compressive strength is one of the mechanical properties of concrete that is directly related to the safety of the structures. Therefore, predicting the compressive strength can facilitate the early planning of material quality management. A series of deep learning (DL) models that suit computer vision tasks, namely the convolutional neural networks (CNNs), are used to predict the compressive strength of ready-mixed concrete. To demonstrate the efficacy of computer vision-based prediction, its effectiveness using imaging numerical data was compared with that of the deep neural networks (DNNs) technique that uses conventional numerical data. Various DL prediction models were compared and the best ones were identified with the relevant concrete datasets. The best DL models were then optimized by fine-tuning their hyperparameters using a newly developed bio-inspired metaheuristic algorithm, called jellyfish search optimizer, to enhance the accuracy and reliability. Analytical experiments indicate that the computer vision-based CNNs outperform the numerical data-based DNNs in all evaluation metrics except the training time. Thus, the bio-inspired optimization of computer vision-based convolutional neural networks is potentially a promising approach to predict the compressive strength of ready-mixed concrete.


Assuntos
Aprendizado Profundo , Algoritmos , Força Compressiva , Redes Neurais de Computação , Reprodutibilidade dos Testes
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