Waste oyster shells (WOS) have the potential to serve as a construction material, offering a sustainable alternative to traditional fine aggregates in the production of WOS concrete. This can play a critical role in reducing environmental issues resulting from the overexploitation of river sand and the haphazard disposal of WOS. Although existing research has predominantly focused on understanding the static mechanical characteristics of concrete when WOS is employed, the dynamic mechanical properties have still received less attention. To understand the impact of WOS as a substitute for fine aggregates on the dynamic mechanical properties of concrete, a series of tests employing Split Hopkinson Pressure Bar (SHPB) were carried out. The findings demonstrate that the peak stress and elastic modulus increase as the WOS substitution ratio (Sr) increases from 0 to 20% but exhibit an exponential decline as Sr increases from 20 to 100%. This response can be explained by the joint effects of the pore-filling effect caused by WOS sand and the increasing air content caused by WOS sand. As Sr increases from 0 to 20%, the pore-filling mechanism becomes predominant as the water absorption rate decreases slightly from 4.31 to 3.83%. However, for Sr increasing from 20 to 100%, the negative influence of the air content becomes the primary contributing factor, where the water absorption rate increases from 3.83 to 14.68%. Furthermore, under the same impact pressure, the concrete with Sr = 20% absorbed the most energy, providing the best dynamic mechanical performance. These findings highlight the potential use of WOS in concrete for improving its dynamic characteristics, promoting both sustainable construction and enhancing the material properties in impact-resistant structures.

The energy-absorbing capacity and friction phenomena of different closed-cell aluminium foam-filled Al tube types are investigated through experimental compression tests. Concerning the kind of investigation, free, radial-constrained and friction tests occurred. The radial-constrained compression test results confirm that the process requires significantly more compression energy than without the constrain. Pushing away different pre-compressed foams inside the aluminium tube, the static and kinematic frictional resistances can be determined and the energy required to move them can be calculated. Knowing the value of the energy required for the frictional resistance, we can obtain how much of the energy surplus in radially inhibited compression is caused by the friction phenomena. The main goal present study is to reveal the magnitude of friction between the foam and the wall of the tube during the radially constrained test. The investigation used 0.4 and 0.7 g/cm3 density closed-cell aluminium foam whilst a compressive test was applied where the force-displacement data were recorded to calculate the absorbed energy due to friction. Considering the results of the test, it can be stated that 18% of the invested energy was used to overcome friction in the case of lighter foam and almost 23% with 0.7 g/cm3 foam during the radial-constrained test.

In this research, we delve into the fascinating dynamics of projectiles and their interactions with materials, with a keen focus on residual velocity - the speed a projectile retains after striking a target. This parameter is pivotal, especially when considering the design of protective barriers in various environments. Traditional methods of gauging residual velocity have been cumbersome, resource-intensive, and occasionally inconsistent. To address these challenges, we introduce an innovative approach using an Artificial Neural Network (ANN) model through MATLAB R2021a. This computerized tool, trained on a rich dataset from prior research, can predict residual velocities by considering multiple factors, including the initial speed of the projectile, its material and shape, and the thickness of the target. This paper meticulously details the development, training, and validation of the ANN model, highlighting its superior accuracy when compared to traditional methods like the Recht-Ipson model. The developed ANN model demonstrated remarkable performance compared to the Recht-Ipson model. During training, it exhibited a Mean Absolute Percentage Error (MAPE) of 0.0259 and a Root Mean Squared Error (RMSE) of 1.5993. For validation, MAPE was 0.0295, and RMSE was 2.2056. In contrast, the Recht-Ipson model displayed higher errors, with MAPE and RMSE values of 0.2349 and 14.1791, respectively. Furthermore, we discuss the potential of the ANN model in predicting not just residual velocities but also absorbed energy, showcasing its versatility. The practical implications of our findings are vast. From designing safer infrastructures in urban settings to enhancing armour systems in military applications, the ANN model\'s predictions can be a cornerstone for innovation.

This study investigates the effects of incorporating various types of nanoparticles, both singularly and in hybrid form, on the low-velocity impact (LVI) response of glass fiber reinforced polymer (GFRP) composites. GFRP composites were fabricated using the hand lay-up method and different weight percentages (wt. %) of multi-walled carbon nanotubes (MWCNT), clay, TiO2, and CuO nanoparticles were added into the matrix of composites. To test the LVI response, 14 types of specimens were fabricated with single and hybrid nanoparticle loadings, and LVI tests were conducted using 5 and 10-cm span dimensions at two levels of subjected energy. The experimental results reveal that specimens with a single loading of MWCNT or nano-clay have a lower maximum contact force compared to pure specimens with fully rebounding behavior. This indicates that neither 5 nor 10 cm spans result in severe damages during the impact tests. Furthermore, incorporating more MWCNTs results in stiffer behavior and more brittleness. The study also explores the synergetic effect of adding hybrid nanoparticles in the fabricated composites and discusses the calculated results for absorbed energy. Finally, scanning electron microscopy (SEM) images are analyzed to evaluate the enhancement mechanisms resulting from the addition of nanoparticles to GFRP composite specimens.

暂无摘要。

Additive manufacturing (AM) enables the production of complex structured parts with tailored properties. Instead of manufacturing parts as fully solid, they can be infilled with lattice structures to optimize mechanical, thermal, and other functional properties. A lattice structure is formed by the repetition of a particular unit cell based on a defined pattern. The unit cell\'s geometry, relative density, and size dictate the lattice structure\'s properties. Where certain domains of the part require denser infill compared to other domains, the functionally graded lattice structure allows for further part optimization. This manuscript consists of two main sections. In the first section, we discussed the dual graded lattice structure (DGLS) generation framework. This framework can grade both the size and the relative density or porosity of standard and custom unit cells simultaneously as a function of the structure spatial coordinates. Popular benchmark parts from different fields were used to test the framework\'s efficiency against different unit cell types and grading equations. In the second part, we investigated the effect of lattice structure dual grading on mechanical properties. It was found that combining both relative density and size grading fine-tunes the compressive strength, modulus of elasticity, absorbed energy, and fracture behavior of the lattice structure.

Irradiance and temperature variations during tidal cycles modulate microphytobenthic primary production potentially by changing the radiative energy balance of photosynthetic mats between immersion and emersion and thus sediment daily net metabolism. To test the effect of tidal stages on the radiative energy budget, we used microsensor measurements of oxygen, temperature, and scalar irradiance to estimate the radiative energy budget in a coastal photosynthetic microbial mat during immersion (constant water column of 2 cm) and emersion under increasing irradiance. Total absorbed light energy was higher in immersion than emersion, due to a lower reflectance of the microbial mat, while most (> 97%) of the absorbed light energy was dissipated as heat irrespective of tidal conditions. During immersion, the upward heat flux was higher than the downward one, whereas the opposite occurred during emersion. At highest photon irradiance (800 μmol photon m-2 s-1), the sediment temperature increased ~ 2.5 °C after changing the conditions from immersion to emersion. The radiative energy balance showed that less than 1% of the incident light energy (PAR, 400-700 nm) was conserved by photosynthesis under both tidal conditions. At low to moderate incident irradiances, the light use efficiency was similar during the tidal stages. In contrast, we found an ~ 30% reduction in the light use efficiency during emersion as compared to immersion under the highest irradiance likely due to the rapid warming of the sediment during emersion and increased non-photochemical quenching. These changes in the photosynthetic efficiency and radiative energy budget could affect both primary producers and temperature-dependent bacterial activity and consequently daily net metabolism rates having important ecological consequences.

Attenuation coefficients of different varieties of gamma irradiated potato (Kufri Chandramukhi, Kufri Jyoti, and Kufri Sindhuri), mango (Himsagar, Langra, Dashehri and Fazli) and prawn (Tiger prawn and Fresh water prawn) of different storage time and physiological stages were determined. After six months storage attenuation coefficient of Kufri Chandramukhi was decreased by 30.8% with decrease of density and moisture content. Decreasing trend of attenuation coefficient during storage was more prominent (almost 50%) in other two varieties of potato. On the other hand in all four varieties, unripe mango consisted of significantly less (p ≤ 0.05) attenuation coefficient (around 11-14%) than the ripe one due to changes in physiological properties and density. Different varieties of prawn had different attenuation coefficients due to subtle differences in their proximate composition. Due to having different attenuation coefficients, different food components, even different varieties of same food component absorbed different gamma radiation energy though exposed to same radiation dose.

There is no consensus over the optimal criterion to define the fatigue life of bone cement in vitro. Fatigue testing samples have been made into various shapes using different surface preparation techniques with little attention being paid to the importance of these variations on the fatigue results. The present study focuses on the effect of test sample shape and surface production method on the fatigue results. The samples were manufactured with two cross sectional shapes: rectangular according to ISO 527 and circular according to ASTM F2118. Each shape was produced using two methods: direct moulding of the cement dough and machining from oversized rods. Testing was performed using two different bone cements: SmartSet GHV and DePuy CMW1. At least 10 samples of each category were tested, under fully reversed tension-compression fatigue stress at ±20MPa, to allow for Weibull analysis to compare results. The growth of fatigue cracks was observed by means of the changes in the absorbed energy and apparent modulus. It was found that fatigue crack growth can be altered by the sample shape and production method; however it is also dependent on the chemical composition of the cement. The results revealed that moulded samples, particularly those based on the ASTM F2118 standard, can lead to up to 5.5 times greater fatigue lives compared to the machined samples of the same cement. It is thus essential, when comparing the fatigue results of bone cement, to consider the effect of production method along with the shape of the test sample.