Engineering Mechanisms Research Articles

Engineering CSFe Bond Confinement Effect to Stabilize Metallic-Phase Sulfide for High Power Density Sodium-Ion Batteries.

Metallic-phase iron sulfide (e.g., Fe7 S8 ) is a promising candidate for high power density sodium storage anode due to the inherent metal electronic conductivity and unhindered sodium-ion diffusion kinetics. Nevertheless, long-cycle stability can not be achieved simultaneously while designing a fast-charging Fe7 S8 -based anode. Herein, Fe7 S8 encapsulated in carbon-sulfur bonds doped hollow carbon fibers (NHCFs-S-Fe7 S8 ) is designed and synthesized for sodium-ion storage. The NHCFs-S-Fe7 S8 including metallic-phase Fe7 S8 embrace higher electron specific conductivity, electrochemical reversibility, and fast sodium-ion diffusion. Moreover, the carbonaceous fibers with polar CSFe bonds of NHCFs-S-Fe7 S8 exhibit a fixed confinement effect for electrochemical conversion intermediates contributing to long cycle life. In conclusion, combined with theoretical study and experimental analysis, the multinomial optimized NHCFs-S-Fe7 S8 is demonstrated to integrate a suitable structure for higher capacity, fast charging, and longer cycle life. The full cell shows a power density of 1639.6Wkg-1 and an energy density of 204.5Whkg-1 , respectively, over 120 long cycles of stability at 1.1Ag-1 . The underlying mechanism of metal sulfide structure engineering is revealed by in-depth analysis, which provides constructive guidance for designing the next generation of durable high-power density sodium storage anodes.

Optimizing incremental SDN upgrades for load balancing in ISP networks

Software defined network (SDN) can dynamically and timely reply to the changes of network states, thus enabling advance traffic engineering mechanisms. To enhance the management ability of the network, Internet Service Providers (ISPs) are upgrading traditional network devices to SDN devices incrementally. In this paper, we study the k-LB problem, i.e., upgrading at most k legacy switches to SDN switches to achieve load balance. We prove that k-LB problem is NP-hard and there is no polynomial time (N+M)1−ϵ-approximation algorithm for any constant ϵ>0 unless P=NP, where N (M) is the number of switches (links) in the network. Nevertheless, we propose an effective greedy algorithm and prove that it reaches an approximation guarantee of cavgcminM, where cavg (cmin) is the average (minimum) link capacity. Furthermore, we show that the greedy algorithm touches the tight lower bound of approximation ratio by extending the inapproximability result. The simulation results from large-scale ISP network topologies illustrate the effectiveness of our algorithm and show that the maximum link utilization can be decreased by 30% on average compared with the SOTA.

Progressive Evolution Model of Fault Water Inrush Caused by Underground Excavation Based on Multiphysical Fields

Underground fault water inrushes are frequent hydrogeological disasters associated with underground mining and tunnel construction projects. In this study, we analyze the water inrush mechanism of underground engineering by building a numerical simulation model to evaluate the process of water inrush, analyze water inrush changes under various working conditions, and consider the fluid-solid coupling effect of rock mass and water. These analyses provide effective suggestions for preventing water inrush from faults. The study establishes a two-dimensional numerical model based on Darcy’s law and plane strain field to analyze water inrush from faults in underground engineering. The analysis shows that factors such as aquifer pressure, permeability between the aquifer and fault zone, and permeability sensitivity coefficient are important considerations that affect the occurrence of water-inrush disasters. The study also identifies the sudden change in water inrush speed at the fault zone and the roadway when the working condition is changed as an indication of the nature of water inrush at the fault. Additionally, the study presents preventive measures such as drainage grouting to ensure the safety of underground engineering constructions. Overall, this research provides important insights into the causes and effects of water inrush from faults and can inform practical measures to mitigate the risks associated with underground engineering.

Editorial for the special issue “Control‐theoretic approaches for systems in the life sciences”

Editorial for the special issue “Control<scp>‐theoretic</scp> approaches for systems in the life sciences”

MCLSG:Multi-modal classification of lung disease and severity grading framework using consolidated feature engineering mechanisms

Human disease detection using medical images with algorithmic severity prediction is unexplored. Deep learning algorithms for disease identification and classification from medical images have been proposed recently. Precision medicine requires more than illness detection. Expert diagnosis and advanced medical examinations are frequently necessary to decrease the likelihood of cross-infection and cater to a patient based on his severity level. To enable the assessment of human disease detection with its severity, we propose the Multi-modal Classification of Lung Disease and Severity Grading (MCLSG) framework from the different medical image modalities using dedicated feature engineering mechanisms. The automatic MCLSG framework consists of pre-processing, automatic feature extraction, classification, and severity analysis. The goal of pre-processing phase is to enhance the image quality and localize the region of interest (ROI) without using any segmentation method. The unwanted image regions are cropped followed by the quality enhancement in the pre-processing. In the automatic feature extraction phase, the optimized Convolutional Neural Network (CNN) layers perform the automatic feature learning and selection using pre-trained parameters. Optimized CNN is then combined with machine-learning classifiers for disease identification. When the disease is detected, MCLSG does automatic disease severity assessments utilizing a consolidated feature engineering technique that includes high-level and low-level characteristics rather than only CNN features. According to the outcome of consolidated feature engineering, we divide patients into four severity levels (mild, moderate, severe, and fatal). The experimental findings show that the proposed MCLSG model is efficient. Overall results show that MCLSG improves the accuracy by 3.5 % for disease detection and 6.8 % for severity level analysis.

Engineering geology and mechanism of multiple landslides in a large open-pit mine: the case of the Copper Mine in Qinghai Province, China

Engineering geology and mechanism of multiple landslides in a large open-pit mine: the case of the Copper Mine in Qinghai Province, China

The creep model based on nonlinear Newton body under different temperature conditions

Mastering the creep deformation characteristics of rock under different temperature conditions is of great significance for studying the long-term stability and deformation mechanism of geotechnical engineering. Based on the classical Burgers model, the creep model under different temperature conditions is established by introducing a nonlinear Newton body. The parameters of the creep model are identified and the influence law of different parameters on rock creep deformation is analyzed. The relationship between model parameters and temperature is quantitatively expressed. The results show that the newly established model can describe the characteristics of the rock in the decay creep stage and the constant creep stage, especially can quantitatively characterize the relationship between the strain and the time of the rock in the tertiary creep under different temperatures conditions. The model fitting curve is highly consistent with the test data, and the correlation coefficient R2 is above 0.98, which thoroughly verifies the accuracy and rationality of the model. It is found that when the temperature is constant, the creep increases with the increase of the shear modulus of the elastomer G1, the shear modulus of the viscoelastic body G2, and the viscosity coefficient of the viscous body η1 in the constant creep stage. The decay creep property of rock is more obvious with the increase of the viscosity coefficient η2, and the axial strain tends to a constant value. The achievement can be used to predict the deformation trend of geotechnical engineering with time under different temperature conditions and provide the theoretical basis for long-term stability analysis.

Synergy mechanism of defect engineering in MoS2/FeS2/C heterostructure for high-performance sodium-ion battery

MoS2 is a promising anode material in sodium-ion battery technologies for possessing high theoretical capacity. However, the sluggish Na+ diffusion kinetics and low electronic conductivity hinder the promises. Herein, a unique MoS2/FeS2/C heterojunction with abundant defects and hollow structure (MFCHHS) was constructed. The synergy of defect engineering in MoS2, FeS2, and the carbon layer of MFCHHS with a larger specific surface area provides multiple storage sites of Na+ corresponding to the surface-controlled process. The MoS2/FeS2/C heterostructure and rich defects in MoS2 and carbon layer lower the Na+ diffusion energy barrier. Additionally, the construction of MoS2/FeS2 heterojunction promotes electron transfer at the interface, accompanying with excellent conductivity of the carbon layer to facilitate reversible electrochemical reactions. The abundant defects and mismatches at the interface of MoS2/FeS2 and MoS2/C heterojunctions could relieve lattice stress and volume change sequentially. As a result, the MFCHHS anode exhibits the high capacity of 613.1 mA h g−1 at 0.5 A g−1 and 306.1 mA h g−1 at 20 A g−1. The capacity retention of 85.0% after 1400 cycles at 5.0 A g−1 is achieved. The density functional theory (DFT) calculation and in situ transmission electron microscope (TEM), Raman, ex-situ X-ray photon spectroscopy (XPS) studies confirm the low volume change during intercalation/deintercalation process and the efficient Na+ storage in the layered structure of MoS2 and carbon layer, as well as the defects and heterostructures in MFCHHS. We believe this work could provide an inspiration for constructing heterojunction with abundant defects to foster fast electron and Na+ diffusion kinetics, resulting in excellent rate capability and cycling stability.

Investigation of the process of formation of pitting of the pusher of the internal combustion engine.

Increasing the reliability of parts working in contact with each other in friction conditions is an important task in the manufacture of any modern machine. When choosing tribological materials, it is necessary to take into account the specifics of working conditions at the contact of friction pair surfaces. In the gas distribution mechanism of an internal combustion engine, the working surfaces of the camshaft cam and the valve tappet during operation experience high contact pressures, fatigue loads. In this regard, for highly accelerated automobile engines, in order to increase the wear resistance of the pusher, it is welded by freezing with white cast iron. In this paper, the process of spalling (formation of pitting) in the surfacing of the pusher during bench tests is considered. It is shown that an increase in the hardness of the working surface of the pusher does not always guarantee the required wear resistance of the material, it is necessary to consider its microstructural state. During the wear process, cementite dendrites can be deformed, sometimes with the formation of microcracks; a network of cracks is present in the pits of pitting. The quantitative ratio of the martensitic and austenitic structural components in the cast iron matrix (at least within the studied limits) does not significantly affect the durability of the pushers. The current requirement for the content of ~40 % cementite in the cast iron microstructure does not guarantee the necessary wear resistance of the material. Based on the results of the study, recommendations were formed on the process of surfacing by freezing white cast iron to improve wear resistance.

An Ion-Engineering Strategy to Design Hollow FeCo/CoFe2 O4 Microspheres for High-Performance Microwave Absorption.

Although assembled hollow architectures have received considerable attention as lightweight functional materials, their uncontrollable self-aggregation and tedious synthetic methods hinder precise construction and modulation. Therefore, this study proposes a bi-ion synergistic regulation strategy to design assembled hollow-shaped cobalt spinel oxide microspheres. Dominated by the coordination-etching effects of F- and the hydrolysis-complex contributions of NH4 + , the unique construction is formed attributed to the dynamic cycles between metal complexes and precipitates. Meanwhile, their basic structures are perfectly retained after reduction treatment, enabling FeCo/CoFe2 O4 bimagnetic system to be obtained. Subsequently, in-depth analyses are conducted. Investigations reveal that multiscale magnetic coupling networks and enriched air-material heterointerfaces contribute to the remarkable magnetic-dielectric behavior, supported by the advanced off-axis electron holography technique. Consequently, the obtained FeCo/CoFe2 O4 composites exhibit excellent microwave absorption performances with minimal reflection losses (RLmin ) as high as -51.6 dB, an effective absorption bandwidth (EAB) of 4.7 GHz, and a matched thickness of 1.4 mm. Thus, this work provides an informative guide for rationally assembling building blocks into hollow architectures as advanced microwave absorbers through bi-ion and even multi-ion synergistic engineering mechanisms.

A Study on Spatial and Temporal Dynamic Changes of Desertification in Northern China from 2000 to 2020

Desertification is of significant concern as one of the world’s most serious ecological and environmental problems. China has made great achievements in afforestation and desertification control in recent years. The climate varies greatly across northern China. Using a long-time series of remote sensing data to study the effects of desertification will further the understanding of China’s desertification control engineering and climate change mechanisms. The moist index was employed in this research to determine the climate type and delineate the potential occurrence range of desertification in China. Then, based on the Google Earth Engine platform, MODIS data were used to construct various desertification monitoring indicators and applied to four machine learning models. By comparing different combinations of indicators and machine learning models, it was concluded that the random forest model with four indicator combinations had the highest accuracy of 86.94% and a Kappa coefficient of 0.84. Therefore, the random forest model with four indicator combinations was used to monitor desertification in the study area from 2000 to 2020. According to our studies, the area of desertification decreased by more than 237,844 km2 between 2000 and 2020 due to the impact of human activities and in addition to climatic factors such as the important role of precipitation. This research gives a database for the cause and control of desertification as well as a reference for national-scale desertification monitoring.

Reform of the Training Program of Intelligent Manufacturing Engineering of Universities in the Steel Industry

To meet the demand of talents in the rapid and sustainable development of the steel manufacturing industry and the needs of the local development of green and intelligent steel technology, this paper presented a reformed training program of intelligent manufacturing of universities for the steel industry. The training program explored the reform plan of talent training objectives, curriculum system, teaching mode, practical links, and operation mechanism of intelligent manufacturing engineering, and built a system with the goal of cultivating innovative ability covering green and intelligent concepts. A new mode of talent cultivation that covers the green and intelligent manufacturing concept and awareness, engineering knowledge, and innovation ability is built, to cultivate high-quality engineering talents who can adapt to the demand of green and intelligent development of steel and other industries. The innovative talent cultivation mode could reconstruct the steel intelligent manufacturing engineering education system and produce a demonstrative effect and good social benefits on the construction of intelligent manufacturing engineering specialty in the industry-featured colleges and universities.

Single Cu Atom Doping on Au11 Nanocluster: Its Implication toward Selectivity in C–C Coupling Reaction

Atom precise metal nanoclusters with customized surface structures are important for understanding the mechanism of surface engineering for appropriate applications. We are reporting a single copper doping on a very widely studied Au11(PPh3)7Cl3 nanocluster, in which one chloride ligand is replaced by one Cu atom. Accordingly, a new bimetal nanocluster Cu1Au11(PPh3)7Cl2 is produced, which consisted of a unique Au–Cu surface motif where the Cu is only bonded with an Au atom. In such a motif, the unsaturated Cu atom acts as an active catalyst for the Sonogashira reaction in contrast to the catalytically inactive Au11 nanocluster. Moreover, it demonstrated a reversed selectivity in the Sonogashira cross-coupling reaction, where the major product obtained was homocoupled Glaser products in contrast to the selectivity of previously reported cluster/bimetallic clusters toward Ullmann or Sonogashira products. Theoretical calculations support the unsaturated Cu to be the active site on the nanocluster (NC) and act like a single-atom catalyst. This highlights the effect of mono copper atom doping on the unique selectivity in the Sonogashira cross-coupling reaction.

An Extended Hydro-Mechanical Coupling Model Based on Smoothed Particle Hydrodynamics for Simulating Crack Propagation in Rocks under Hydraulic and Compressive Loads

A seepage model based on smoothed particle hydrodynamics (SPH) was developed for the seepage simulation of pore water in porous rock mass media. Then, the effectiveness of the seepage model was proved by a two-dimensional seepage benchmark example. Under the framework of SPH based on the total Lagrangian formula, an extended hydro-mechanical coupling model (EHM-TLF-SPH) was proposed to simulate the crack propagation and coalescence process of rock samples with prefabricated flaws under hydraulic and compressive loads. In the SPH program, the Lagrangian kernel was used to approximate the equations of motion of particles. Then, the influence of flaw water pressure on crack propagation and coalescence models of rock samples with single or two parallel prefabricated flaws was studied by two numerical examples. The simulation results agreed well with the test results, verifying the validity and accuracy of the EHM-TLF-SPH model. The results showed that with the increase in flaw water pressure, the crack initiation angle and stress of the wing crack decreased gradually. The crack initiation location of the wing crack moved to the prefabricated flaw tip, while the crack initiation location of the shear crack was far away from the prefabricated flaw tip. In addition, the influence of the permeability coefficient and flaw water pressure on the osmotic pressure was also investigated, which revealed the fracturing mechanism of hydraulic cracking engineering.

Molecular insights of nanozymes from design to catalytic mechanism.

Emerging as cost-effective potential alternatives to natural enzymes, nanozymes have attracted increasing interest in broad fields. To exploit the in-depth potential of nanozymes, rational structural engineering and explicit catalytic mechanisms at the molecular scale are required. Recently, impressive progress has been made in mimicking the characteristics of natural enzymes by constructing metal active sites, binding pockets, scaffolds, and delicate allosteric regulation. Ingenious in-depth studies have been conducted with advances in structural characterization and theoretical calculations, unveiling the "black box" of nanozyme-catalytic mechanisms. This review introduces the state-of-art synthesis strategies by learning from the natural enzyme counterparts and summarizes the general overview of the nanozyme mechanism with a particular emphasis on the adsorbed intermediates and descriptors that predict the nanozyme activity The emerging activity assessment methodology that illustrates the relationship between electrochemical oxygen reduction and enzymatic oxygen reduction is discussed with up-to-date advances Future opportunities and challenges are presented in the end to spark more profound work and attract more researchers from various backgrounds to the flourishing field of nanozymes.

Study on Improvement Characteristics of a Novel Geotextile with Stitched Transverse Ribs

Geotextile is one of the reinforcement materials adopted in many engineering structures. Conventional geotextiles have a limited reinforcement effect due to the insufficient friction strength between geotextiles and soils. This paper proposes a novel type of geotextile with stitched transverse ribs to improve the reinforcement effect. A series of large-scale direct shear tests have been conducted, and the improvement characteristics between conventional geotextiles, geogrids, and the novel geotextiles have been studied. The results show that the novel stitched transverse rib geotextiles can significantly increase the shear strength compared to conventional geotextiles and geogrids. Moreover, due to the restraint and friction effect of ribs on the soils, the reinforcement effect of the novel geotextile is increased with increasing ribs. Insights from this study can provide a new understanding of the novel stitched transverse ribs geotextile’s reinforcement mechanism in engineering.

Experimental study on mechanical properties of single fracture-hole red sandstone

Various fractures and holes in the natural rock mass affected the mechanical properties of the rock mass and the safety construction of engineering. In this study, we investigated the mechanical properties of a single fracture-hole rock specimen using particle flow code 2D (PFC2D) numerical simulation software and through laboratory tests. We analysed the failure behaviours and mechanical properties of the rock specimen with a single fracture-hole specimen under different fracture angles. The failure modes of single fractured rock samples with different fracture angles were revealed. The fracture propagation and stress evolution of the rock specimen with a single fracture-hole under different fracture angles were investigated. The experimental results shown that the peak strength, peak strain, elastic modulus, initial fracture stress, and damage stress of the single fracture-hole rock specimen with different fracture angles were significantly less than those of the intact rock specimen. Moreover, fracture hole defects accelerated the generation of fractures and promote the failure of the rock specimen. The failure modes were divided into Y, inverted Y, and V types. Before the rock specimen fractures, the stress concentration area was mainly distributed at both ends of the fracture. The stress concentration area at both ends of the fracture gradually decreased, and the stress concentration area near the hole gradually increased as the fracture angle increased. By experiments, the acoustic emission of the model had gone through three stages: initial, steady growth, and rapid decline. The size of the inclination angle affected the number of acoustic emission hits and the generation of acoustic emission signals. Failure behaviours of the rock specimen with a single fracture-hole were systematically investigated, which could promoted the development of fracture rock mechanics and improved the understanding of instability failure mechanism in rock engineering, such as nuclear wasted treatment engineering and deep underground engineering.

Semi-analytical solutions of shallow water waves with idealised bottom topographies

Analysing two-dimensional shallow water equations with idealised bottom topographies have many applications in the atmospheric and oceanic sciences; however, restrictive flow pattern assumptions have been made to achieve explicit solutions. This work employs the Adomian decomposition method (ADM) to develop semi-analytical formulations of these problems that preserve the direct correlation of the physical parameters while capturing the nonlinear phenomenon. Furthermore, we exploit these techniques as reverse engineering mechanisms to develop key connections between some prevalent ansatz formulations in the open literature as well as derive new families of exact solutions describing geostrophic inertial oscillations and anticyclonic vortices with finite escape times. Our semi-analytical evaluations show the promise of this approach in terms of providing robust approximations against several oceanic variations and bottom topographies while also preserving the direct correlation between the physical parameters such as the Froude number, the bottom topography, the Coriolis parameter, as well as the flow and free surface behaviours. Our numerical validations provide additional confirmations of this approach while also illustrating that ADM can also be used to provide insight and deduce novel solutions that have not been explored, which can be used to characterise various types of geophysical flows.

Analysis of High-frequency Combustion Noise Generation Mechanism in Pre-chamber Jet Combustion Gasoline Engine

Analysis of High-frequency Combustion Noise Generation Mechanism in Pre-chamber Jet Combustion Gasoline Engine

Construction and validation of a reduced mechanism in a diesel engine fueled with 2-methylfuran-diesel

The addition of 2-methylfuran into diesel has been studied extensively to deal with the fossil energy crisis and reduce pollutant emissions. However, the chemical reaction mechanism of the engine combustion model related to 2-methylfuran is rarely reported. In this study, a reduced 2-methylfuran chemical reaction mechanism was developed by the directed relation graph with error propagation, reaction path analysis, sensitivity analysis and rate of production analysis. Then it was coupled with a diesel mechanism, and the pre-exponential factor A of the Arrhenius equation was adjusted for specific reactions to finally forma reduced 2-methylfuran-diesel mechanism containing 55 species and 190 reactions for application in combustion modeling under engine related conditions. Based on the experimental data in the literature, the predicted ignition delay time and species mole fractions by the mechanism were validated. Also, the three-dimensional simulation data was compared with the test data of cylinder pressure and heat release rate from a single-cylinder diesel engine under different working conditions. The simulation results of the mechanism with certain stability and accuracy are basically consistent with the experimental data and can be used to analyze the characteristics of 2-methylfuran-diesel combustion on diesel engines.