Static Properties Research Articles

Behavior of steel fiber-reinforced coal gangue concrete beams under impact load

In order to promote the use of new sustainable steel fibers (SF) reinforced coal gangue aggregates (CGA) concrete, impact tests were performed in this paper. The impact resistance of steel fiber-reinforced coal gangue concrete was investigated using a self-developed drop-weight facility. The test variables were the CGA replacement rate (0 %, 50 %, and 100 %), the SF volume content (0 %, 0.75 %, and 1.5 %), and the drop height of the drop-weight (0.5 m and 1.0 m). Using 15 kg of hard steel as a drop-weight, the drop-weight impact test was performed on steel fiber-reinforced coal gangue concrete beams with a span of 300 mm; the damage pattern, impact reaction force-time, displacement-time relationships, and energy absorbed by steel fiber-reinforced coal gangue concrete beams were studied. The test shows that, compared with natural aggregate, CGA reduces concrete's static mechanical properties and impact resistance, and adding SF improves the static mechanical properties and impact resistance of coal gangue concrete. As the CGA replacement rate increased from 0 % to 50 % and 100 %, the reaction force of impact of the specimens decreased by 2.54 %− 6.06 % and 3.69 %− 12.33 %. The SF volume content was increased from 0 % to 0.75 % and 1.5 %, and the reaction force of impact of the specimens was increased by 23.05 %− 32.34 % and 72.27 %− 81.84 %, respectively. The impact resistance of steel fiber-reinforced concrete beams under impact loading was investigated numerically using a nonlinear explicit finite element model in LS-DYNA. The Finite Element results were validated with experimental results. Based on the validated finite element model, a parametric study was carried out to investigate the effects of coal gangue replacement rate, steel fiber volume content, and drop height of the drop weight on the behavior of the beams. This study might provide a basis for the future engineering project applications of steel fiber-reinforced coal gangue concrete under impact conditions.

Dynamics of Droplets Moving on Lubricated Polymer Brushes.

Understanding the dynamics of drops on polymer-coated surfaces is crucial for optimizing applications such as self-cleaning materials or microfluidic devices. While the static and dynamic properties of deposited drops have been well characterized, a microscopic understanding of the underlying dynamics is missing. In particular, it is unclear how drop dynamics depends on the amount of uncross-linked chains in the brush, because experimental techniques fail to quantify those. Here we use coarse-grained simulations to study droplets moving on a lubricated polymer brush substrate under the influence of an external body force. The simulation model is based on the many body dissipative particle dynamics (MDPD) method and designed to mimic a system of water droplets on poly(dimethylsiloxane) (PDMS) brushes with chemically identical PDMS lubricant. In agreement with experiments, we find a sublinear power law dependence between the external force F and the droplet velocity v, F ∝ vα with α < 1; however, the exponents differ (α ∼ 0.6-0.7 in simulations versus α ∼ 0.25 in experiments). With increasing velocity, the droplets elongate and the receding contact angle decreases, whereas the advancing contact angle remains roughly constant. Analyzing the flow profiles inside the droplet reveals that the droplets do not slide but roll, with vanishing slip at the substrate surface. Surprisingly, adding lubricant has very little effect on the effective friction force between the droplet and the substrate, even though it has a pronounced effect on the size and structure of the wetting ridge, especially above the cloaking transition.

Intrinsic flame-retardant epoxy resin based on phosphorus-containing liquid imidazole compound: Simultaneously improving fire safety, mechanical property and heat resistance

In this work, two phosphorus-containing liquid imidazole compounds with different phosphorus oxidation states (1,1′-(phenylphosphanediyl)bis(1H-imidazole) (DCPPI) with + 1 valence phosphorus, and imidazole-phenylphosphate (PPOAI) with + 3 valence phosphorus) were designed and synthesized. Both of DCPPI and PPOAI were used as curing agents to obtain intrinsic flame-retardant epoxy resin (EP-DCPPI and EP-PPOAI), in which the imidazole group was used as the curing group of EP, and the phosphorus-containing group was directly connected to the EP crosslinking network. On the one hand, the efficient flame-retardant groups containing + 1 or + 3 valence phosphorus were incorporated into the EP system to obtain excellent flame-retardant properties; on the other hand, the introduction of phenylphosphine or phenoxyphosphine groups in the molecular chain of EP greatly enhanced the interaction between molecular chains, adjusted crosslinking density and endowed EP with excellent tensile strength and toughness. Compared with imidazole cured EP (EP-MZ), the peak heat release rate (PHRR) of EP-15DCPPI and EP-15PPOAI decreased by 70 % and 68 %, and the total heat release rate (THR) decreased by 37 % and 36 %, respectively. Meanwhile, EP-15DCPPI passed UL-94 V-0 rating, and the limiting oxygen index (LOI) reached 36.1 %. EP-15PPOAI passed UL-94 V-1 rating and the LOI reached 29.1 %. The flame-retardant mechanism was analyzed and discussed. Compared with EP-MZ, the dynamic and static mechanical properties of EP-15DCPPI and EP-15PPOAI were enhanced simultaneously, and the glass transition temperature (Tg) was obviously increased.

Static mechanical properties and damage evolution characteristics of selected rocks in diversion tunnel under uniaxial loading

An in-depth understanding of the mechanical properties and damage and fracture mechanism of selected rocks in a diversion tunnel plays an important role in promoting the efficient construction and safety of rock blasting excavation in a diversion tunnel. To study the mechanical properties and damage evolution characteristics of selected rocks in diversion tunnels under uniaxial loading, the uniaxial compression and uniaxial splitting tests of granite and tuff were carried out. In terms of mechanical properties, the evolution characteristics of complete stress-strain curves, instantaneous modulus-strain curves, and input energy density-strain curves were analyzed. In the aspect of damage characteristics, the macroscopic and mesoscopic failure modes were analyzed and the damage fracture mechanism was revealed. Compression-shear failure mainly occurred in granite and tuff under uniaxial compression, showing the characteristics of elastic-brittle fracture failure. Both granite and tuff showed a failure mode of coexistence of “compression-shear failure zone at the loading ends” and “tension-shear failure zone in the middle” under uniaxial splitting. The compression-shear fracture of granite was relatively smooth, and the matrix and mineral particles produced fine particles due to friction in the process of shear slip. The compression-shear fracture of tuff was relatively rough and the characteristics of shear slip were not prominent enough. The fracture failure of granite and tuff was mainly caused by the common fracture of rock matrix and mineral particles. Based on the Lemaitre equivalent strain principle, the pre-peak-post-peak two-stage damage constitutive model established by Weibull statistical distribution theory can accurately describe the static stress-strain relationships of granite and tuff under uniaxial compression.

Examine the static and dynamic mechanical properties of alkali-treated Cannabis sativa plant fiber-reinforced composites

Examine the static and dynamic mechanical properties of alkali-treated Cannabis sativa plant fiber-reinforced composites

FeZrN Films: Static and Microwave Magnetic Properties

FeZrN Films: Static and Microwave Magnetic Properties

An experimental study of the static magnetic properties of Co thin films

An experimental study of the static magnetic properties of Co thin films

Design of low-frequency circular metastructure isolators with high-load-bearing capacity

Traditional vibration isolation structures cannot work effectively for low-frequency vibration under heavy loads, due to the inherent contradiction between the high-static and low-dynamic stiffness of these structures. Although the challenge can be effectively addressed by introducing a negative stiffness mechanism, the existing structures inevitably have complex configurations. Metastructures, a class of man-made structures with both extraordinary mechanical properties and simple configurations, provide a new insight for low-frequency vibration isolation technology. In this paper, circular metastructure isolators consisting of some simple beams are designed for low-frequency vibration, including a single-layer isolator and a double-layer isolator, and their static and dynamic characteristics are studied, respectively. For the static characteristic, the force–displacement and stiffness–displacement curves are obtained by finite element simulation; for the dynamic characteristic, the vibration transmissibility curves are obtained analytically and numerically. The result shows that the circular nonlinear single-layer isolator has excellent low-frequency isolation performance, and the isolation frequency band will decrease about 20 Hz when the isolated mass is fixed at 1.535 kg, compared with a similar circular linear isolator. These static and dynamic properties are well verified through experiments. Our work provides an innovative approach for the low-frequency vibration isolation and has wide potential applications in aeronautics.

Study on static and dynamic mechanical properties and microstructure of silica fume-polypropylene fiber modified rubber concrete

Through tests and micro-observations, the static and dynamic mechanical properties and microstructure of rubber concrete samples modified with varying amounts of silica fume and polypropylene fiber content were explored. The results indicate that incorporation of silica fume and polypropylene fiber can effectively enhance the performance of rubber concrete. Moreover, at 10% and 0.1% of silica fume and polypropylene fiber content respectively, rubber concrete’s compressive strength, splitting tensile strength, flexural strength, and dynamic compressive strength reached maxima. Furthermore, microstructure characteristic analysis indicated that inadequate adhesion between rubber particles and the matrix is responsible for compromised bearing capacity in unmodified rubber concrete. However, with the addition of silica fume and polypropylene fiber, the fiber binds the rubber particles closely with the matrix, while the silica fume fills the gaps between the matrix components. This combination results in rubber concrete with a denser internal structure and enhances its bearing capacity significantly.

A Robust Approach to Malware Detection through Ensemble learning

Abstract: With the proliferation of digital threats in today's interconnected world, the need for efficient and effective automated malware detection systems has become paramount. Traditional signature-based methods often fail to keep pace with the evolving landscape of malware, necessitating the development of more sophisticated techniques. In this paper, we propose a robust approach to automated malware detection leveraging ensemble learning techniques. Ensemble learning, which combines the predictions of multiple base models, has demonstrated remarkable success in various domains, including cybersecurity. Our approach harnesses the diversity of ensemble methods to enhance the detection accuracy and robustness against adversarial attacks. By integrating diverse base classifiers such as decision trees, random forests, support vector machines, and neural networks, our ensemble model learns to effectively discriminate between benign and malicious software samples. Furthermore, we introduce novel feature engineering strategies tailored to capture the intricate characteristics of malware. These features encompass a wide range of attributes, including static file properties, dynamic behavioural patterns, and frequency-based representations. Leveraging these rich feature sets, our ensemble model can generalize well across different types of malware families and variants.

Estimating Position-Dependent and Anisotropic Diffusivity Tensors from Molecular Dynamics Trajectories: Existing Methods and Future Outlook.

Confinement can substantially alter the physicochemical properties of materials by breaking translational isotropy and rendering all physical properties position-dependent. Molecular dynamics (MD) simulations have proven instrumental in characterizing such spatial heterogeneities and probing the impact of confinement on materials' properties. For static properties, this is a straightforward task and can be achieved via simple spatial binning. Such an approach, however, cannot be readily applied to transport coefficients due to lack of natural extensions of autocorrelations used for their calculation in the bulk. The prime example of this challenge is diffusivity, which, in the bulk, can be readily estimated from the particles' mobility statistics, which satisfy the Fokker-Planck equation. Under confinement, however, such statistics will follow the Smoluchowski equation, which lacks a closed-form analytical solution. This brief review explores the rich history of estimating profiles of the diffusivity tensor from MD simulations and discusses various approximate methods and algorithms developed for this purpose. Besides discussing heuristic extensions of bulk methods, we overview more rigorous algorithms, including kernel-based methods, Bayesian approaches, and operator discretization techniques. Additionally, we outline methods based on applying biasing potentials or imposing constraints on tracer particles. Finally, we discuss approaches that estimate diffusivity from mean first passage time or committor probability profiles, a conceptual framework originally developed in the context of collective variable spaces describing rare events in computational chemistry and biology. In summary, this paper offers a concise survey of diverse approaches for estimating diffusivity from MD trajectories, highlighting challenges and opportunities in this area.

DecoPa: Query Decomposition for Parallel Complex Event Processing

Systems for Complex Event Processing (CEP) enable the detection of predefined patterns in event streams. While the evaluation of CEP queries is computationally hard, scalability may be achieved by parallelization. Yet, existing approaches for parallel CEP are driven by static query properties, such as partitioning keys and states of the evaluation model. They largely neglect the rates with which processing units may ingest and compare events for query evaluation. In this paper, we present an approach for parallel CEP that is based on a flexible decomposition of CEP queries. Our idea is to guide the decomposition by the sustainable throughput of each processing unit, in order to maximize the overall performance. To this end, we introduce DecoPa plans for parallel CEP, provide a cost model for them, elaborate on their correctness and optimality, and present an algorithm for their construction. Experiments using a DecoPa implementation in Flink illustrate throughput gains of up to 12 orders of magnitude compared to state-of-the-art approaches.

A new quantum hydrodynamic description of ferroelectricity in spiral magnets

The strong coupling between magnetism and ferroelectricity was found in rare-earth manganites, where the electric polarization could be induced by special magnetic ordering. There is no theoretical model that would allow us to study the static and dynamic properties of electric polarization in strongly correlated magnetic dielectrics. In the presented research, we have taken the main step toward the construction of such a fundamental model and made a direct connection between the microscopic Katsura–Nagaosa–Balatsky theory and Mostovoy’s phenomenological model for magnetically induced polarization. A novel description of the ferroelectricity of spin origin is proposed within the framework of the many-particle quantum hydrodynamics method. It is applied to the study of cells of magnetic ions, where the electric dipole moment is proportional to the vector product of spins. Our approach is based on the many-particle Pauli equation, where the influence of an external magnetic field is considered. We define the electric dipole moment operator of the ion cell and introduce the macroscopic polarization as the quantum mechanical average of that operator. We formulate a model for the description of nonequilibrium polarization and derive a new polarization evolution equation. The polarization switching in ferroelectric magnets with the spiral spin-density-wave state is considered, and we demonstrate that the proposed model yields known results and can predict novel effects. The dynamic magnetoelectric effect can be investigated by employing this novel equation to study the evolution of polarization.

Static mechanical properties and failure behaviors of self-piercing riveted joints in aluminum alloy 5A06 after aging

This paper conducts an investigation on the static mechanical properties and failure behavior of self-piercing riveted joints in aluminum alloy 5A06 after being subjected to the aging process. The study involves three distinct categories of joint specimens: original specimens, 1-year aged specimens and 1-year aged specimens that have been additionally heat-treated at 200 °C. The research findings affirm that strain aging is responsible for a reduction in the peak strength of the joints. Furthermore, the weakest failure chain within the self-piercing riveted joint shifts towards the upper sheet due to a more significant reduction in internal stress experienced by the upper plate. This leads to a failure model characterized by upper sheet pull-off. Through Weibull distribution analysis, it has been established that the 5 % lower limit value for the strength of the SPR joint experiences an 86 % decline following 1-year aging. In practical terms, this means that for a vehicle structure with 7000 riveting points will lose an overall structural strength equivalent to the initial strength of 1000 riveting points within one year.

Static properties evaluation for laser deposition repaired TA15 components based on a constitutive model considering annealing heat treatment

In remanufacturing field, the laser deposition repair technology combined with annealing heat treatment is widely used for repairing the damaged TA15 titanium alloy components owning to its low cost and high efficiency. But evaluating the properties of repaired components is still a challenging due to the damage test of the continued used components. To solve this, a new evaluation method for the static properties of the laser deposition repaired TA15 components is proposed in this study based on a new constitutive model (named as LRA constitutive model) with considering the annealing temperature and holding time in annealing heat treatment. The physical meanings of the model parameters are analyzed and illustrated from the static tensile experiments of several laser deposition repaired TA15 materials with different annealing heat treatment. In comparison with the experimental results and the predictions from the traditional constitutive model, the LRA constitutive model is validated and shows higher precision (>94 %) than the traditional constitutive model. After the application in the evaluation of static properties of a laser deposition repaired TA15 aircraft panel, the results exhibit that the proposed method has the advantage of low cost and high efficiency.

New Branched Iron(III) Complexes in Fluorescent Environment Created by Carbazole Moieties: Synthesis and Structure, Static Magnetic and Resonance Properties

The branched complexes of Schiff bases with various iron(III) salts, named G2-[L2Fe]+A− (A− is NO3−, Cl−, PF6−), were synthesized using the condensation reaction between carbazole derivatives of salicylic aldehyde and N’-ethylethylenediamine and characterized by various spectroscopic methods (GPC, IR, 1H NMR, UV/Vis). The studies revealed that the coordination of the two ligand molecules to metal occurs through the nitrogen ions and oxygen atom of azomethine to form a homoleptic system. All the synthesized coordination compounds were examined for their thermal, optical, and magnetic features. Static magnetic measurements showed that only G2-[L2Fe]Cl was in a single-phase HS state, whereas the Fe(III) ions of G2-[L2Fe]NO3 and G2-[L2Fe]PF6 at room temperatures were in mixed low-spin (LS, S = 1/2) and high-spin (HS, S = 5/2) states: 58.9% LS/41.1% HS for G2-[L2Fe]NO3, 56.1% LS and 43.9% HS for G2-[L2Fe]PF6. All G2-[L2Fe]+A− complexes demonstrate antiferromagnetic exchange interactions between neighboring Fe(III) ions. The ground spin state at 2.0 K revealed a Brillouin contribution from non-interacting LS ions and a proportion of the HS Fe(III) ions not participating in AFM interactions: 57%, 18%, and 16% for G2-[L2Fe]Cl, G2-[L2Fe]NO3 and G2-[L2Fe]PF6, respectively. EPR measurements confirmed the presence of magnetically active HS and LS states of Fe(III) ions and made it possible to distinguish two HS types-with strong low-symmetry (I-type) and weak, distorted octahedral environments (II-type). It was shown that G2-[L2Fe]+A− complexes are magnetically inhomogeneous and consist of two magnetic sub-lattices: AFM-correlated chains in layers from the I-type HS Fe(III) centers and dynamic short-range AFM ordered LS/II-type HS Fe(III) centers in the paramagnetic phase located between the layers.

Design and Optimization of NR-Based Stretchable Conductive Composites Filled with MoSi2 Nanoparticles and MWCNTs: Perspectives from Experimental Characterization and Molecular Dynamics Simulations.

Stretchable conductive composites play a pivotal role in the development of personalized electronic devices, electronic skins, and artificial implant devices. This article explores the fabrication and characterization of stretchable composites based on natural rubber (NR) filled with molybdenum disilicide (MoSi2) nanoparticles and multi-walled carbon nanotubes (MWCNTs). Experimental characterization and molecular dynamics (MD) simulations are employed to investigate the static and dynamic properties of the composites, including morphology, glass transition temperature (Tg), electrical conductivity, and mechanical behavior. Results show that the addition of MoSi2 nanoparticles enhances the dispersion of MWCNTs within the NR matrix, optimizing the formation of a conductive network. Dynamic mechanical analysis (DMA) confirms the Tg reduction with the addition of MWCNTs and the influence of MoSi2 content on Tg. Mechanical testing reveals that the tensile strength increases with MoSi2 content, with an optimal ratio of 4:1 MoSi2:MWCNTs. Electrical conductivity measurements demonstrate that the MoSi2/MWCNTs/NR composites exhibit enhanced conductivity, reaching optimal values at specific filler ratios. MD simulations further support experimental findings, highlighting the role of MoSi2 in improving dispersion and mechanical properties. Overall, the study elucidates the synergistic effects of nanoparticles and nanotubes in enhancing the properties of stretchable conductive composites.

Dynamical and static spin properties in the α-T3 lattice: Insights from Kane–Mele–Hubbard model analysis

Our study delves into the dynamic and static spin structure factors of the α-T3 lattice, employing the Green's function approach, within the framework of the Kane–Mele and Hubbard model Hamiltonian. The dynamical spin susceptibility is directly related to the inelastic cross-section of the neutron beam interacting with the layer. Within this framework, analysis of the α-T3 lattice's spin excitation modes necessitates a thorough examination of the effect of the magnetic field, on-site Coulomb repulsion strength, and the spin-orbit coupling (SOC) parameter. This investigation is carried out by calculating the correlation function of the transverse components of spin density operators. Our findings reveal intriguing trends: The intensity of peaks in the inelastic cross-section varies with changes in on-site Coulomb repulsion. Moreover, our temperature-dependent assessment of the static spin structure factor indicates the manifestation of ferromagnetic behavior in the α-T3 lattice when α equals 0.5. Furthermore, the combined influence of SOC and magnetic fields amplifies the magnetic long-range order within the α-T3 lattice. The ability to manipulate the static spin structure factor and the imaginary dynamical transverse spin susceptibility holds promise across diverse domains, spanning from magnetic storage and spintronics to quantum computing and medical imaging.

The Role of Lipid Intrinsic Curvature in the Droplet Interface Bilayer.

Model bilayers are constructed from lipids having different intrinsic curvatures using the droplet interface bilayer (DIB) method, and their static physicochemical properties are determined. Geometrical and tensiometric measurements are used to derive the free energy of formation (ΔF) of a two-droplet DIB relative to a pair of isolated aqueous droplets, each decorated with a phospholipid monolayer. The lipid molecules employed have different headgroup sizes but identical hydrophobic tail structure, and each is characterized by an intrinsic curvature value (c0) that increases in absolute value with decreasing size of headgroup. Mixtures of lipids at different ratios were also investigated. The role of curvature stress on the values of ΔF of the respective lipid bilayers in these model membranes is discussed and is illuminated by the observation of a decrement in ΔF that scales as a near linear function of c02. Overall, the results reveal an association that should prove useful in studies of ion channels and other membrane proteins embedded in model droplet bilayer systems that will impact the understanding of protein function in cellular membranes composed of lipids of high and low curvature.

Static Magnetic Properties and Morphological Behaviour of Mn and Zn Substituted Ca-hexaferrite by Ceramic Technic

Synthesis of M-type hexagonal ferrite compounds, Ca(CoTi)0.5(MnZn)x/2Fe11-xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2) prepared by ceramic technic. Mn and Zn ions substituted to find the magnetic characterizationat magnetic field of 10 kOe. XRD and SEM study have been done for getting the hexagonal structure of these samples. Due to the substitution of Mn and Zn ions saturation magnetization increases and magnetocrystalline anisotropy decreases. Due to the sub-latice site distribution the variations in magnetic parameters have been observed. Because of Mn and Zn ions substitution Curie temperature decreases by weakening of superexchange interaction. These materials can be used for various applications such aspermanent magnetic material, magnetic recording media, ferrofluids, sensors, microwave absorbing materials, ceramic magnets in loud speakers and rotors in small DC motors by studying various magnetic parameters from VSM characterization.