Search

Reaction-bonded boron carbide composites were fabricated by molten silicon infiltration of diamond-containing boron carbide preforms. The effects of diamond particle size on the microstructure, mechanical and tribological properties of reaction-bonded boron carbide composites were investigated. Fine diamond particles (≤7.7 µm) completely reacted with silicon generating nano silicon carbide particles, which bonded the boron carbide particles forming a 3-D ceramic skeleton and improving the flexural strength of the composites. Coarser diamond (≥24 µm) particles were retained protected by a dense SiC layer generated from the reaction of diamond and molten silicon. A "core-shell" structure with the retained diamond as the "core" and with the reaction formed silicon carbide as the "shell" formed. Relief structures were established on the composites' surface during the wear process, greatly reducing the friction coefficient and improving the wear resistance. [ABSTRACT FROM AUTHOR]

Detecting volatile organic compounds is essential to improving the environment and human health. This study prepared a novel composite of hollow SnO 2 /ZnO cubes using a self-template hydrothermal method followed by a calcination process. The morphology and structure of the composites were characterized using a series of analysis techniques, and the formation mechanism of a hollow cube-like structure was explored. Compared to the hollow SnO 2 cube sensor, the hollow SnO 2 /ZnO cube sensor exhibited a strong response (148–100 ppm formaldehyde), fast response/recovery time (15 s/25 s), good linearity (R2 = 0.995), good repeatability, and excellent stability. The superior gas sensing property of the hollow SnO 2 /ZnO cubes was attributed to the combined advantages of hollow structures and heterojunctions. [ABSTRACT FROM AUTHOR]

Reaction-bonded boron carbide (RBBC) composites have great potential for large-scale industrial production owing to their low cost and flexible product size. In this work, RBBC composites with various carbon additions were fabricated by liquid Si infiltration. The morphology of carbon sources is decisive for the morphology of reaction-formed SiC grains at 1550 °C. The effects of carbon sources on the microstructure and mechanical properties of the composites were studied. The as-prepared composites achieve a flexural strength of up to 575 MPa and a fracture toughness of up to 5.1 MPa/m2. The enhancement of the strength and toughness was attributed to the formation of defects-containing nano-SiC grains and continuous ceramic skeletons composed of boron carbide and nano-SiC. In addition, high aspect ratio plate-like SiC grains also allow a considerable improvement in the mechanical properties, even if they are not uniformly distributed. [ABSTRACT FROM AUTHOR]

• For the first time prevent the dissolution and reaction loss of boron carbide particles by using carbon-coated boron carbide particles as raw materials in the reaction-bonding of boron carbide by Si infiltration. • A ceramic skeleton of the nano-SiC particles-coated and -bonded boron carbide particles and resultant mechanical properties. • In situ reaction to form nano silicon carbide particles in reaction bonded boron carbide composites. To tackle the dissolution problem of boron carbide particles in silicon infiltration process, carbon-coated boron carbide particles were fabricated for the preparation of the reaction-bonded boron carbide composites. The carbon coating can effectively protect the boron carbide from reacting with liquid Si and their dissolution, thus maintaining the irregular shape of boron carbide particles and preventing the growth of boron carbide particles and reaction formed SiC regions. Furthermore, the nano-SiC particles, originated from the reaction of the carbon coating and the infiltrated Si, uniformly coated on the surfaces of boron carbide particles, thus forming a ceramic skeleton of the nano-SiC particles-coated and -bonded boron carbide particles. The Vickers hardness, flexural strength and fracture toughness of the composites can be increased by 26 %, 45 %, and 37 % respectively, by using carbon-coated boron carbide particles as raw materials. [ABSTRACT FROM AUTHOR]

• Vialinin A protects neurons against oxidative stress injury after ischaemic stroke. • Vialinin A enhances the activation of Keap1-Nrf2-ARE signaling pathway. • USP4 binds to and mediates the deubiquitination modification of Keap1. • Vialinin A enhances the ubiquitination of Keap1 and promoting its degradation. • USP4 upregulation reverses the neuron protection of vialinin A on ischaemic stroke. Oxidative stress is known as a hallmark of cerebral ischaemia‒reperfusion injury and it exacerbates the pathologic progression of ischaemic brain damage. Vialinin A, derived from a Chinese edible mushroom, possesses multiple pharmacological activities in cancer, Kawasaki disease, asthma and pathological scarring. Notably, vialinin A is an inhibitor of ubiquitin-specific peptidase 4 (USP4) that shows anti-inflammatory and antioxidative properties. However, the precise effect of vialinin A in ischaemic stroke, as well as its underlying mechanisms, remains largely unexplored. The present research focuses on the impacts of vialinin A on oxidative stress and explores the underlying mechanisms involved while also examining its potentiality as a therapeutic candidate for ischaemic stroke. Mouse ischaemic stroke was conducted by MCAO surgery. Vialinin A was administered via lateral ventricular injection at a dose of 2 mg/kg after reperfusion. Subsequent experiments were meticulously conducted at the appropriate time points. Stroke outcomes were evaluated by TTC staining, neurological score, Nissl staining and behavioural analysis. Co-IP assays were operated to examine the protein-protein interactions. Immunoblot analysis, qRT-PCR, and luciferase reporter assays were conducted to further investigate its underlying mechanisms. In this study, we initially showed that administration of vialinin A alleviated cerebral ischaemia‒reperfusion injury-induced neurological deficits and neuronal apoptosis. Furthermore, vialinin A, which is an antioxidant, reduced oxidative stress injury, promoted the activation of the Keap1-Nrf2-ARE signaling pathway and increased the protein degradation of Keap1. The substantial neuroprotective effects of vialinin A against ischaemic stroke were compromised by the overexpression of USP4. Mechanistically, vialinin A inhibited the deubiquitinating enzymatic activity of USP4, leading to enhanced ubiquitination of Keap1 and subsequently promoting its degradation. This cascade caused the activation of Nrf2-dependent antioxidant response, culminating in a reduction of neuronal apoptosis and the amelioration of neurological dysfunction following ischaemic stroke. This study demonstrates that inhibition of USP4 to activate Keap1-Nrf2-ARE signaling pathway may represent a mechanism by which vialinin A conferred protection against cerebral ischaemia‒reperfusion injury and sheds light on its promising prospects as a therapeutic intervention for ischaemic stroke. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • This review systematically analyzes the effect of interface issues on solid-state electrolytes for lithium batteries. • Two-dimensional materials-based modification strategy for solid-state electrolytes and mechanisms are presented. • The current challenges and issues of solid-state electrolytes in lithium batteries are addressed. Lithium-ion batteries have been widely used in mobile electronic devices and electric vehicles, but the safety issues of lithium-ion batteries have become increasingly prominent owing to the risk of leak out and explosion with liquid electrolytes. Solid-state electrolytes (SSEs) with high ionic conductivity and low cost are considered as one of the most attractive alternatives to replacing liquid electrolytes. However, the poor interfacial compatibilities of SSE in lithium batteries lead to the failure, which severely hinders their development. Recent studies have shown that two-dimensional (2D) layered materials can improve the interface stability of SSE to lithium metal. In this Review, we will mainly introduce the fundamentals of SSEs and interface issues, and then summarize 2D materials-based modification strategy for SSEs. Recent advances have been highlighted in the aspects of using 2D materials for improving the interface of SSEs, which are very promising for energy applications. The availability of the 2D materials offers a rich playground, which not only improves the electrochemical performance of solid-state lithium batteries, but also conceives deep understanding the mechanism of interface modulation. Lastly, the perspective is provided to address the current challenges and issues of SSEs in lithium batteries. [ABSTRACT FROM AUTHOR]

• Evaluation of the fatigue performance of ancient brick masonry structures. • The fatigue stress–strain curve presented obvious three-stage development characteristics of sparse–dense–sparse. • The fatigue strain evolution curve showed a typical " S " structure with three distinct stages. In this study, a low-cycle fatigue test was conducted using an MTS793 electro-hydraulic servo fatigue testing machine and a VIC-3D image acquisition system to explore the effects of different loading frequencies and upper limit stress amplitudes on the fatigue damage characteristics of ancient brick masonry. The test results indicated prominent fatigue damage characteristics and shaping of the ancient brick masonry under cyclic load. The axial deformation development of ancient brick masonry consists of three stages that result in fatigue damage evolution and macroscopic fracture. These stages include a large maximum cyclic stress amplitude, low loading frequency, and a larger hysteresis loopback during the loading and unloading area. The plastic stress variable of each loop increases, and the fatigue life of the specimen decreases with the increase in the sample fatigue damage rate. [ABSTRACT FROM AUTHOR]

It is of significant importance to understand the role of glycerol additive for the improvement of the energy recovery during tobacco-waste pyrolysis. Utilizing ReaxFF-based molecular dynamic simulation, herein, we systematically studied the pyrolysis mechanism of tobacco with different concentrations of glycerol (5%, 10%, 16.5%, 20%, 25%) at different temperatures (1800 K, 2000 K, 2300 K, 2500 K, 2800 K). The calculation shows that a temperature of 2000 K is the optimal temperature for producing methanol and ethanol. Furthermore, the concentration of glycerol had a significant effect on promoting methanol production at high temperatures. Methanol's main generation pathway was influenced by temperature and glycerol concentration, while the primary pathway of ethanol production was independent of them. Moreover, a pyrolysis reaction framework was created for methanol and ethanol production, and their main formation reactions were validated. Finally, a chemical kinetic analysis of the pyrolysis process confirmed the accuracy of the ReaxFF MD simulations. [Display omitted] ● ReaxFF-based MD simulation was used for the studies of the tobacco-waste pyrolysis. ● Higher temperatures facilitate methanol and ethanol production, but excessively high temperatures hinder their formation. ● Glycerol additive boosts methanol production at high temperatures. ● Methanol production pathway varies with the glycerol concentration. ● Methyl, methoxy, hydroxyl, and hydrogen radicals are crucial in methanol and ethanol production. [ABSTRACT FROM AUTHOR]

• Evaluation of the fatigue performance of ancient brick masonry structures. • The curves of p–S–N fatigue equation based on Weibull distribution was established. • The fatigue stress–strain curve presented obvious three-stage development characteristics of sparse–dense–sparse. • The fatigue strain evolution curve showed a typical " S " structure with three distinct stages. Urban expansion and diversified traffic aggravate the damage and deterioration of ancient buildings. It is crucial to evaluate the long-term fatigue performance of ancient brick masonry structures for the safety and maintenance of ancient buildings. A series of indoor tests were conducted on the ancient brick masonry. The images for the whole process of the test were collected using VIC-3D technology. The relationship between the stress level and the number of failure cycles under compressive fatigue load and the stress–strain evolution under different stress levels were determined. A mathematical model of p-S-N fatigue life prediction based on probability was proposed, which comprehensively considered the maximum stress level, stress range, number of load cycles, and survival probability. The equivalent fatigue life of ancient brick masonry specimens under each failure probability obeys Weibull distribution, and then the fatigue life of masonry can be predicted at any expected confidence level. The test results provide reliable theoretical and data support for fatigue deterioration and life prediction of ancient masonry structures in service. [ABSTRACT FROM AUTHOR]

Wind flow turbulence is known to have a major influence on the pedestrian-level wind (PLW) environments, particularly around a building. The elevated design of a building, as a special feature, proved to improve pedestrian-level weak wind conditions in high-density cities. The present study aims to assess three turbulence models, the detached eddy simulation (DES), the steady-state RANS (SRANS), and the unsteady-state RANS (URANS), in their simulation of the PLW flow turbulence concerning wind gust. The simulated mean wind velocities around isolated buildings with and without an elevated design were compared with those obtained from a wind tunnel experiment. The effects of mesh resolution and inflow fluctuating algorithm on the performance of the DES model were thoroughly evaluated. The DES model can better reproduce the mean flow fields than the other two models. Finally, the unsteady fluctuations of wind flow around the buildings with and without the elevated design are analyzed in terms of instantaneous wind velocity, lift coefficient, energy spectral density, and turbulence intensity. The predicted lift coefficient and Strouhal number are approximately 0.01 and 0.09, respectively, which is consistent with what are reported in the literature. Modifications of the frequency of vortex shedding, periodical wind flow pattern, and the normalized wind gust flow fields around the two types of buildings are compared in detail. The work reveals that transient turbulent flow pattern can be reasonably obtained with the DES model, indicating the potential of using the DES for PLW gust assessments in urban planning. [ABSTRACT FROM AUTHOR]

Wind flow turbulence plays a critical role in the pedestrian level wind environment, particularly for the airflow around buildings with specific architectural features. The elevated design, a feature was proved to improve the pedestrian level weak wind conditions in high-density cities in our earlier study. This present study aims to further investigate the pedestrian level wind flow turbulence in an elevated building surrounding. The predictions were conducted by comparing the CFD simulation and a wind tunnel experiment. Specifically, the Detached Eddy Simulation (DES), the Steady-state and the Unsteady-state RANS (SRANS and URANS), were assessed. The effects of mesh resolutions and inflow fluctuating algorithms on the performance of the DES model were thoroughly evaluated. DES can better reproduce the mean flow fields than the other two models. The unsteady flow fluctuations around the elevated building are analyzed with energy spectral density. Meanwhile, the periodical wind flow fields around the elevated building are accurately obtained. [ABSTRACT FROM AUTHOR]

The pedestrian level wind environment is seriously deteriorated by moderated local wind flow in a densely built-up subtropical city like Hong Kong. In order to improve the weak wind condition, the lift-up design has been used for some time. However, there is a lack of understanding and quantitative assessment of its modification on the pedestrian level wind comfort around different building configurations under different wind directions. This paper aims to study the effects of lift-up design in four common building configurations on the wind comfort via computational fluid dynamics (CFD) simulations. The turbulence model and numerical method are firstly validated by comparing the simulated wind flow data with the wind tunnel test results. The validated model is then utilized to simulate the four building configurations, including the “─”, “L”, “U” and “□” shaped buildings. The mean wind velocity ratio ( MVR ) and mean wind velocity change ratio ( Δ MVR ) are employed to identify the wind comfort and to quantitatively evaluate the improvements due to the lift-up design. Results show that the lift-up design can improve the wind comfort in building surroundings and its influence is highly dependent on the incident wind direction. Specifically, the wind comfort is better under the oblique wind direction than the other two wind directions. These findings can provide us a better understanding of the lift-up design and will be helpful in better precinct planning. [ABSTRACT FROM AUTHOR]

Taking into account outdoor thermal comfort in the urban design stage can potentially enhance the livability of a city. This study aims to demonstrate an outdoor thermal comfort prediction method using measured thermal parameters and simulated wind velocities. This is done by first comparing the CFD simulation results of wind velocities around a single building with and without elevated design with those obtained from a wind tunnel experiment, and two turbulence models, the Delayed Detached Eddy Simulation (DDES) and the RNG k-ε model, were assessed. The mean velocity field obtained using DDES model has better agreement with the wind tunnel measurements, especially in the wake region and at the open space beneath the elevated building. It is shown that the building elevation modified the mean flow pattern around a building. Then the potential impact on pedestrian thermal comfort was assessed using a simplified method by combining the predicted wind velocity and the on-site monitored radiant and air temperatures and air humidity on two summer days. It is revealed that the elevated design improves the thermal comfort only in the limited neighboring area, but that the open space underneath the elevated building provides much better thermal comfort in the summer conditions. The work demonstrates that CFD simulation of wind conditions can be used to assess outdoor thermal comfort in the planning stage without being coupled with thermal simulation. [ABSTRACT FROM AUTHOR]

[Display omitted] • The maximum flotation yield of 84.25% was achieved when TOAM mixed with kerosene in the flotation process. • The TOAM adsorption on the LRC surfaces was promoted by hydroxyl group contained in TOAM. • The greatest PBAI value was 0.84 while mixing kerosene with TOAM. • The lowest reciprocal flotation rate constant of 10.25 was obtained when mixed collector more than 2.5 kg/t. Here, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), flotation experiments, and low-rank coal (LRC) particle-bubble attachment measurements (using the particle-bubble attachment index [PBAI]) were employed to explore the effects of collector mixtures on the flotation kinetics of LRC particles. At a flotation dosage of 3.0 kg/t, the greatest flotation recovery (62.51%) for a single collector was achieved using triethanolamine oleic acid monoester (TOAM), compared with using kerosene or 2-ethylhexanol. At the same dosage, the maximum flotation recovery increased to 84.25% when using a mixture of TOAM with kerosene. However, when the collector dosage was more than 2.5 kg/t, the fitting result of the flotation rate constant obtained by mixing TOAM with kerosene was larger than those obtained by mixing 2-ethylhexanol with either kerosene or TOAM. Furthermore, when the attachment time exceeded 100 ms, the greatest PBAI value (0.84) was obtained when mixing kerosene with TOAM, rather than when mixing 2-ethylhexanol with kerosene or TOAM. Thus, this study presented an improved mixture of TOAM and kerosene that can aid the flotation performance of LRC and could be regarded as potential application for LRC flotation industrial. [ABSTRACT FROM AUTHOR]