Hasil untuk "Materials of engineering and construction. Mechanics of materials"

Abeer Syed, Enshirah Da’na, Amel Taha et al.

Heavy metal contamination is a serious threat to water resources as it has been associated with carcinogenicity, mutagenicity, and toxicity. With the presence of heavy metals in water bodies reported from all over the globe, there is an urgent need for innovative water treatment strategies. The main goal of this study is to enhance the adsorption affinity of poly(acrylonitrile-co-methyl methacrylate) (P(AN-co-MMA)) nanofiber membrane for heavy metals by decorating the nanofiber membrane with greenly synthesized CoFe _2 O _4 nanoparticles. Field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM) images confirmed the uniform dispersion of 30–40 nm CoFe _2 O _4 nanoparticles within the P(AN-co-MMA) nanofiber membrane, having an average fiber diameter of 269 nm. x-ray diffraction (XRD) analysis showed the formation of highly crystalline CoFe _2 O _4 nanoparticles without impurities. The CoFe _2 O _4 nanoparticles exhibited type-IV isotherm, indicating the formation of mesoporous/macroporous materials with a specific surface area of 36.8 m ^2 g ^−1 . Thermal gravimetric analysis (TGA) demonstrated that both P(AN-co-MMA) and P(AN-co-MMA)CoFe _2 O _4 begin to decompose at around 340 °C. The competitive adsorption behavior of the CoFe _2 O _4 , P(AN-co-MMA), and P(AN-co-MMA)CoFe _2 O _4 was studied to determine their selectivity towards Pb ^2+ , Hg ^2+ , and Cd ^2+ . The results showed a superior affinity of CoFe _2 O _4 nanoparticles for Cd ^2+ , with 100% removal within a concentration range of 20–80 ppm, compared to 50% removal using P(AN-co-MMA)CoFe _2 O _4 , and zero removal with P(AN-co-MMA). For Hg ^+ , the efficiency of removal by the CoFe _2 O _4 was the highest followed by P(AN-co-MMA), and then P(AN-co-MMA) CoFe _2 O _4 . Pb ^2+ showed exclusive affinity for the CoFe _2 O _4 nanoparticles only. The presented eco-friendly nanocomposite presents a promising, efficient, and selective adsorbent for heavy metal removal from wastewater to address water pollution.

Shan-Ju Yeh, Yi-Chuan Wang, Wei-Chien Fang et al.

Impairment of upper limb function is common after a stroke and is closely linked to decreased functional independence in activities of daily living. Robot-assisted training has been used in clinical settings to improve hand function in stroke patients; however, many existing devices are costly and require specialized training to operate. This study aimed to propose a novel powered hand exoskeleton (EO) and verify its effectiveness on upper extremity function in people with chronic stroke. Thirty participants were randomly assigned to either the experimental group or the control group. Each participant underwent 30 min interventions twice a week for 8 weeks. The experimental group received 15 min of conventional therapy followed by 15 min of training with the powered hand EO, while the control group received 30 min of conventional therapy. The primary outcome measures included the Fugl-Meyer Assessment for upper extremity function (FMA-UE), the Box and Block Test (BBT), and handgrip dynamometer. Assessments were conducted at baseline and then at 4-week intervals throughout the 8-week period. Results showed that, after the 8-week intervention, the average changes in FMA-UE scores for the experimental group were significantly greater than those for the control group (<i>p</i> < 0.01). A clear upward trend in both FMA-UE and BBT scores was observed in the EO group. Statistical analysis revealed significant improvements in the overall, proximal, and distal components of the FMA-UE scores (all <i>p</i> < 0.01) and in BBT scores (both <i>p</i> < 0.05) in the EO group compared to the control group at 4 and 8 weeks, respectively. However, no significant differences in grip strength were observed between the groups at either time point. Our findings suggest that the proposed powered hand EO is both feasible and safe for training the impaired hand in stroke survivors. Given the characteristics of the device, it has potential for use in hand rehabilitation aimed at regaining upper extremity function.

Brandon K. Phan, Kuan-Hsuan Shen, Rishi Gurnani et al.

Yang Li, Jingwei Guo, Jie Yang et al.

Reducing the interface damage of Cu-Al friction pairs under extreme conditions is a problem that urgently needs to be solved. In this work, a strategy of 5 wt% MnS/7075 Al fabricated via powder metallurgy was proposed to break off the predicament. Comprehensive evaluation was conducted on the friction and wear performance of the oxide-dispersion-strengthened copper (ODS-Cu) friction pair under 0-30A current carrying conditions at peak electrical loading (30 A), the MnS/7075 Al composite reduced the friction coefficient from 0.393 to 0.320 (−18.3%) and the wear rate from 0.022% to 0.0015% (−93%) relative to powder metallurgy (PM) 7075 Al. The lubrication mechanism is attributed to the formation of a continuous MnS-derived lubricating layer at the tribo-interface, which synergistically interacts with Al _2 O _3 generated through Al matrix surface oxidation during frictional processes, establishing a composite protective structure that effectively suppresses Al adhesive transfer phenomena. The composite achieves synergistic optimization of friction reduction and wear resistance, providing theoretical insights for designing highly reliable Cu-Al friction pairs in extreme environments.

Karthik Adiga, Mervin A Herbert, Shrikantha S Rao et al.

Friction Stir Processing is a state-of-the-art technology for microstructure refinement, material property enhancement, and fabrication of surface composites. Machine learning approaches have garnered significant interest as prospective models for modeling various production systems. The present work aims to develop four machine learning models, namely linear regression, support vector regression, artificial neural network and extreme gradient boosting to predict the influence of FSP parameters such as tool rotational speed, tool traverse speed and groove width on ultimate tensile strength of friction stir processed AA8090/SiC surface composites. These models were developed through Python programming and the original dataset was divided into 80% for the training phase and 20% for the testing phase. The performance of the models was evaluated by root mean squared error, mean absolute error and R ^2 . Based on the results and graphical visualization, it was observed that the XGBoost model outperformed other models with high accuracy in predicting UTS of AA8090/SiC surface composites.

Hangming Shen, Xingzhe Zhao, Lihong Yang et al.

In this study, a novel methodology for the fabrication of gradient porous structures is introduced, predicated upon the phase evolution characteristics of immiscible polymer blends. Initially, a comprehensive flow-phase field dynamics model is developed. This model couples the principles of phase field theory and the dynamics of fluid flow to the two-phase evolution process, facilitating a numerical simulation of the phase evolution. Subsequently, the phase field parameters of model are determined and combined with the temperature field, thereby enabling a targeted and controlled fabrication of gradient porous structures. Finally, the efficacy and practical applicability of the proposed methodology are substantiated through the construction of illustrative examples. This approach, as delineated herein, provides a robust framework for the efficient design and realization of intricate, interconnected gradient porous structures with potential applications in various scientific and engineering domains.

Shagun Kainth, Piyush Sharma, O.P. Pandey

Rapid growth in socio-economic requirements and climatic change has put much pressure on the quality of water resources. To prevent the future shortage of fresh water and to keep up with the current demand for water, wastewater reuse, and recycling are among the most pressing issues that must be addressed immediately. So far, many technologies have been used to remove both inorganic and organic pollutants from wastewater. Unfortunately, modern water treatment technologies are still out of reach financially for many developing nations, making it difficult for them to eliminate these toxins. Moreover, increasing environmental toxicity from solid waste exposures is also a major cause of worry. Intending to combat these issues, research efforts have increased to develop an efficient, eco-friendly and low cost biosorbent from agricultural waste to treat wastewater. As a result, there has been an increased focus on identifying locally and regionally accessible agriculture wastes for the removal of heavy metals/metalloids and dyes. This article aims to review a multidisciplinary approach to handle agriculture waste as a potential resource for wastewater treatment. A comprehensive discussion is included on the fundamentals of the biosorption and the involved mechanism. The strategies to improve the efficiency of biosorbents are discussed. In addition, current developments in various biosorbents derived from different agricultural waste and their application to remove toxic elements using diverse methods have been reviewed to set the stage for further investigation. Finally, regeneration of biosorbents and current challenges to implement biosorbents are addressed. This article will help to bridge the gap between laboratory findings and industrial application, leading to the development of more efficient systems for removing pollutants.

Advances in Materials Science and Engineering

Advances in Materials Science and Engineering

Amjad Saleh El-Amoush, Salman A. Al-Duheisat

Abstract High-carbon structural steel wires were prestressed to various levels in a plasma hydrogenation environment and then pulled in a slow strain rate test (SSRT). The effect of plasma hydrogenation under different prestressing levels on the material's tensile response and hydrogen embrittlement was noted. It was found that the ultimate tensile strength (UTS), yield strength, and ductility of the steel wire samples are decreased by plasma hydrogenation and prestressing levels. The more drastic decrease in the UTS, yield strength, and ductility is found in the plasma hydrogenated prestressing steel to a higher prestressing level. Moreover, the hydrogen embrittlement index of the steel wire samples is significantly increased by plasma hydrogenation and prestressing level. The highly plasma hydrogenated prestressing steel wire samples exhibit complete brittle fracture. A mixed mode of fracture, i.e., ductile and brittle, was observed at the surface of the plasma hydrogenated prestressing steel wire samples at lower levels. The hydrogen embrittlement areas at the fracture surfaces of steel wire samples are observed to increase with plasma hydrogenation and prestressing levels. More severe hydrogen cracking and blistering resulted in the fracture surfaces of plasma-hydrogenated prestressing steel wire samples with higher levels.

Mohammad Idris Rasuli

Low-calcium Fly ash-based alkali-activated materials (AAM) have some extraordinary properties such as high fire resistance and low shrinkage. However, they have lower strength and high setting time when curing at ambient temperature conditions. Therefore, this research aimed to improve the strength and setting time of low-calcium fly ash-based AAM curing at ambient temperature conditions. The effect of the changes in concentration and modulus of sodium silicate and curing condition of the materials were studied on the properties of the AAM. Fly ash type II, 32% sodium metasilicate pentahydrate, 32 and 56% sodium disilicate solution, 8M sodium hydroxide, and standardized were used. Using 32% sodium disilicate solution significantly improved the flowability of mortar. Moreover, it increased the compressive strength and remarkably decreased the setting time of AAM at ambient temperature curing. The decrease in the concentration of sodium disilicate has a significant influence on the reactivity of fly ash.

Morvan, Dominique, Accary, Gilbert, Meradji, Sofiane et al.

The aim of this short review is to present the progress made in wildland fire modelling during the last 50 years and the intellectual track followed by wildland fires models, from fully empirical models in the 60s, to semi-empirical ones in the 70s, to fully physical models at the end of the 90s. During the last period, the large diffusion of HPC methods substantially contributed to the development of multiphase formulations applied to wildland fire modelling. Many studies have particularly focused on the effects of various parameters (vegetation, topography, atmosphere) affecting the behaviour of a fire front propagating through a forest fuel layer.

DUAN Peng, LIU Zong-de, TAO Xiang-qian, GU Shu-chao

At present, the changes of microstructure and mechanical properties of T23 steel after served for more than 50 000 h have been less studied.In this work, with using the heat-delivery surface tubes of a 600 MW super-critical boiler as research object, the T23 steel final reheater tubes at various positions after about 80 000 h of service time were tested by microstructure analysis, tensile properties tests at room temperature and 525 ℃ temperature, and the deterioration degree and difference in mechanical properties between back and meet smoke side of tubes after long-term service were investigated further.Results showed that the coarse M6C carbide apparently grew and precipitated at grain boundary, and the microstructure of samples presented obvious aging characteristics.As for the mechanism properties, all T23 tube samples showed badly degradation in tensile properties, and they could not meet the usage requirement.Moreover, there was no significant difference in microstructure between the tubes at the front and back of smoke side, but the sample at the front smoke side showed an obvious decline in tensile properties in the comparison of that at the back smoke side, indicating that the long-term high temperature flue gas scour in the furnace had a significant effect on the performance of samples at the front smoke side.

Xilin ZHAO, Daheng ZHANG, Hang MING

A strategy of compensating DC tie line inertia by differential control of energy storage was proposed in this paper. First, through the analysis of AC/DC transmission model and the inertia characteristics of DC tie line, a two zone AC/DC hybrid AGC system model considering inertia compensation was constructed. Then, energy storage output control was proposed to change the transmission power of DC tie line to form the inertia performance of tie line power change. On this basis, aiming at the negative effect of capacitance value on DC voltage in the process of energy storage extraction, the inertia compensation control strategy with superimposed energy storage differential was designed to improve the inertial response ability of the system. Finally, the feasibility and effectiveness of the proposed method were verified by comparing the simulation results of different load disturbance deviations and tie line overload rates.

Yukari Katsura, Masaya Kumagai, Takushi Kodani et al.

Data mining from published papers can generate large experimental datasets that have been overlooked in computational materials informatics. We developed an open web system Starrydata2 to accelerate a comprehensive digitization of data of materials from as-reported plot images in published papers, without sample selection based on performance. By plotting results obtained from our dataset on experimental thermoelectric properties of 434 samples of rock-salt-type (PbTe-type) thermoelectric materials, we revealed differences in electronic structure of parent compounds PbTe, PbSe, PbS, and SnTe from just experimental data. We observed that the calculated Seebeck coefficients were fairly consistent with experimental data for n-type PbTe but not for p-type PbTe, indicating possible modifications in its valence-band electronic structure. We evaluated the electron relaxation time τel from 207 reported samples of n-type PbTe by combining calculations and experimental data. We found that τel is not a constant but varies by at least two orders of magnitude. Achieving long τel was suggested to be critical in increasing the thermoelectric figure of merit ZT.

E. V. Shagilova

Introduction. The possibility of automated checking the works of participants of the Olympiads in programming is considered. The architecture and operation of the server part of the check system of performing the Olympiad programming tasks is described. Materials and Methods. The technologies of MySQL, PHP, C ++, JavaScript, HTML, and CSS are considered as the application framework. The test program is implemented in C ++ for operating systems of the Windows NT family. Research Results. The opportunity of the automated check of the Olympiad participants’ works in a real-time mode is fulfilled. A program-tester of the system is developed to check the programming Olympiad works. Discussion and Conclusions. As a result of the analysis of the global network and client/server technology operation, capabilities for the organization of interaction of the application with Internet-resources are defined. The developed application has proved expediency and efficiency of the interoperability of the application and Internet-resources.

Bogdan I. Tsykaniuk, Andrii S. Nikolenko, Viktor V. Strelchuk et al.

李德军, 李泽林, 赵志刚 et al.

The effect of single roll soft reduction (6~20mm) and reduction position (1^#〜6^#roll) on central carbon segregation and macrostructure of 180mmx180mm casting billet of high carbon steel SWRH92B (/%: 0.71C, 0.22Si, 0.64Mn, 0.010P, 0.006S) has been tested and studied. Results show that as solid fraction fs is 0.45~0.63 the soft reduction is available to decrease central carbon segregation of casting billet, and as the solid fraction fs is more than 0.82 the shrinkage cavity of billet can not be eliminated and the central carbon segregation can not be decreased； in condition of soft reduction 6~20mm, with increasing reduction the central carbon segregation decreases from 1.15 to 1.04, and the cracks occur easily in billet as the soft reduction is more than 15mm；compared with weak secondary cooling ( water ratio 0.65L/kg) and the ultra weak secondary cooling ( water ratio 0.40L/kg) is more favorable to control central carbon segregation；by comprehensive analysis it is obtained that with casting speed 1.3 m/min, mold stirring 300A and 5Hz, and secondary cooling water ratio 0.40 L/kg, the central carbon segregation and macrostructure of steel SWRH72B 180mmx180mm casting billet are better by single roll soft reduction 15mm at 5^#roll.

Paulo Rangel Rios, Janaina da Costa Pereira Torres de Oliveira, Valmir Torres de Oliveira et al.

The effect of non-random nuclei location and the efficiency of microstructural descriptors in assessing such a situation are studied. Cellular automata simulation of recrystallization in two dimensions is carried out to simulate microstrutural evolution for nuclei distribution ranging from a periodic arrangement to clusters of nuclei. The simulation results are compared in detail with microstrutural descriptors normally used to follow transformation evolution. It is shown that the contiguity is particularly relevant to detect microstructural deviations from randomness. This work focuses on recrystallization but its results are applicable to any nucleation and growth transformation.