Search

Soda-Lime Glass (SLG) has been widely used in the creation of highly-functionalised optical devices. However, machining of SLG easily resulted in various defects. Among these defects, edge chipping (EC) can be treated as the most damageable in terms of both mechanical properties and optical performances. Although efforts have been paid to this topic, previous investigations (i) focused on edge chipping in low strain rate, which was 101-102 times lower than the ones in real machining, (ii) assumed edge chipping shape as circular, while the experiments in this work proved this assumption might be inaccurate in high strain rate circumstances, and (iii) were experimental efforts, resulting in limited knowledge of process principles. To fill this gap, this paper aims to propose an analytical model to calculate the size and the shape of edge chipping in scratch of soda-lime glass with the special consideration of strain-rate hardening effect. A series of experimental trials were performed to validate the model accuracy under different parameters. The details in scratching process were discussed by force analysis. A typical model application was given as well, which was designing the machining strategy based on the proposed model so that a required region with limited edge chipping can be obtained. Considering the research gaps mentioned above, the key findings in this paper are expected to be meaningful and helpful to provide references in the real fabrication of high-valued optical devices made of SLG.

After the emergence of the pandemic, repurposed drugs have been considered as a quicker way of finding potential antiviral agents. SARS-CoV-2 3CLpro is essential for processing the viral polyproteins into mature non-structural proteins, making it an attractive target for developing antiviral agents. Here we show that Vitamin K3 screened from the FDA-Approved Drug Library containing an array of 1,018 compounds has potent inhibitory activity against SARS-CoV-2 3CLpro with the IC50 value of 4.78 ± 1.03 μM, rather than Vitamin K1, K2 and K4. Next, the time-dependent inhibitory experiment was carried out to confirm that Vitamin K3 could form the covalent bond with SARS-CoV-2 3CLpro. Then we analyzed the structure-activity relationship of Vitamin K3 analogues and identified 5,8-dihydroxy-1,4-naphthoquinone with 9.8 times higher inhibitory activity than Vitamin K3. Further mass spectrometric analysis and molecular docking study verified the covalent binding between Vitamin K3 or 5,8-dihydroxy-1,4-naphthoquinone and SARS-CoV-2 3CLpro. Thus, our findings provide valuable information for further optimization and design of novel inhibitors based on Vitamin K3 and its analogues, which may have the potential to fight against SARS-CoV-2.

Hydrophobic modified silica/exfoliated graphite nanoplatelets aerogel (M-SiO2/xGnP) were successfully prepared via surface modification of silica/xGnP alcogel and followed by ambient pressure drying. Afterwards, form-stable PCMs in which capric–palmitic acids eutectic (CA–PA) was confined in the prepared aerogels were obtained by vacuum infiltration. Characterization of the prepared form-stable PCMs revealed that both the hydrophobic modification and the doping of xGnP could effectively improve the loading of CA–PA in the aerogel. The unmodified silica aerogel could not adsorb CA–PA, while the loading of CA–PA in the surface modified pure silica aerogel supported form-stable PCM and the unmodified silica/xGnP aerogel supported form-stable PCM were 24.2 wt% and 44.4 wt%, respectively. Besides, the hydrophobic modification and the doping of xGnP showed significant synergistic effect. The loading of CA–PA in the M-SiO2/xGnP supported form-stable PCM (FPCM/xGnP-20-48) could attain 78.9 wt% when the M-SiO2/xGnP was obtained by modifying the alcogel with 20 vol% trimethyl chlorosilane for 48 h. The FPCM/xGnP-20-48 not only had high latent heat and good thermal reliability, but also exhibited significantly improved thermal conductivity and alleviated supercooling due to the effective thermal conductive network formed by xGnP and the promoted heterogeneous nucleation of CA–PA at interfaces with aerogel.

Corundum abrasives with good chemical stability can be fabricated into various free abrasives and bonded abrasive tools that are widely used in the precision machining of various parts. However, these abrasives cannot satisfy the machining requirements of difficult-to-machine materials with high hardness, high strength, and strong wearing resistance. Although superhard abrasives can machine the above-mentioned materials, their dressing and manufacturing costs are high. By contrast, ceramic corundum abrasives fabricated by sol–gel method is a cost-effective product between conventional and superhard abrasives. Ceramic corundum abrasives exhibit self-sharpening and high toughness. In this review, the optimization methods of ceramic corundum abrasive properties are introduced from three aspects: precursor synthesis, particle shaping, and sintering. Firstly, the functional mechanism of seeds and additives on the microstructural and mechanical properties of abrasives is analyzed. Specifically, seeds can reduce the phase transition temperature and improve fracture toughness. The grain size and uniformly dense structure can be controlled by applying an appropriate amount of multicomponent additives. Then, the urgent need of engineering application and machinability of special shape ceramic corundum abrasives is reviewed, and three methods of abrasive shaping are summarized. The micromold replication technique is highly advanced and can be used to prepare functional abrasives. Additionally, the influence of a new sintering method, namely, two-step sintering technique, on the microstructural and mechanical performance of ceramic corundum abrasives is summarized. Finally, the challenge and developmental trend of the optimization of ceramic corundum abrasives are prospected.

Mussel-inspired surface modification has received significant interest in recent years because of its simplicity and versatility. The deposition systems are still mainly limited to molecules with catechol chemical structures. In this paper, we report a novel deposition system based on a monophenol, vanillic acid (4-hydroxy-3-methoxybenzoic acid), to fabricate metal-phenolic network coatings on various substrates. The results of the water contact angle and zeta potential reveal that the modified polypropylene microfiltration membrane is underwater superhydrophobic and positively charged, showing applications in oil/water separation and dye removal. Furthermore, the single-face modified Janus membrane is promising in switchable oil/water separation. The results demonstrate a novel example of the metal-monophenolic deposition system, which expands the toolbox of surface coatings and facilitates the understanding of the deposition of phenols.

Rotating components such as rotating beams and plates are working in complex physical environments subjected to nonuniform distribution of their own materials, vibration caused by external excitation may result in work instability, structural fatigue and the like, so the dynamic analysis of rotating structures is of great significance. Based on the nonlocal elasticity theory and Timoshenko beam model, the vibration of a rotating functionally graded piezoelectric nanobeam is investigated. First, the dynamic governing equations and corresponding boundary conditions are derived by the Hamiltonian principle. Then, the governing equations and boundary conditions are discretized by the differential quadrature method. Subsequently, the vibration characteristics of nanobeams are analyzed after detailed numerical calculations. The effects of various parameters including rotational velocity, nonlocal parameter, functional gradient index, length–height geometry ratio and external voltage on the vibration characteristics under different boundary conditions are examined. Finally, the numerical results show that these parameters have non-negligible effects on the natural frequencies and modal shapes. The dynamics of rotating functionally graded nanobeams are affected by both external kinematic and voltage factors and inherent scale factor and their coupling effects. In particular, a nonlinear small-scale effect is observed for a rotating functionally graded piezoelectric nanobeam, which may be useful to the design and optimization of the nano-electro-mechanical system including the rotating structures.

In order to provide the effective reinforcement and lubrication for reducing the friction on the interface of the grinding wheel and workpiece during the high-efficiency deep grinding of difficult-to-machine materials, an in-house developed porous composite-bonded (Cubic Boron Nitride) CBN wheel with graphene nanoplatelets was explored to meet the increasing demand for industrial purpose. It can be found from experimental study that by adding the appropriate concentration of graphene, 0.01 wt%, both of the flexural strength and tribology performance have been enhanced in the graphene-modified porous composite-bonded CBN wheel, and then the related grinding wheel was fabricated to perform the grinding experiments on the Ti–6Al–4V titanium alloy (TC4). It has been found that by adding the graphene the sharpness of the abrasives on the surface of the grinding wheel always keeps at a certain range and the grinding wheel may have self-sharpening ability which can guarantee the stability during the high-efficiency deep grinding process. Finally, by considering process parameters in this study the graphene-modified porous composite-bonded CBN grinding wheel could be used to achieve the high-efficiency deep grinding of TC4 as well as guarantee its surface quality under the grinding wheel speed of 80 m/s, grinding depth of 0.1 mm and workpiece feed speed of 0.6 m/min.

Aluminum alloy is the main structural material of aircraft, launch vehicle, spaceship, and space station and is processed by milling. However, tool wear and vibration are the bottlenecks in the milling process of aviation aluminum alloy. The machining accuracy and surface quality of aluminum alloy milling depend on the cutting parameters, material mechanical properties, machine tools, and other parameters. In particular, milling force is the crucial factor to determine material removal and workpiece surface integrity. However, establishing the prediction model of milling force is important and difficult because milling force is the result of multiparameter coupling of process system. The research progress of cutting force model is reviewed from three modeling methods: empirical model, finite element simulation, and instantaneous milling force model. The problems of cutting force modeling are also determined. In view of these problems, the future work direction is proposed in the following four aspects: (1) high-speed milling is adopted for the thin-walled structure of large aviation with large cutting depth, which easily produces high residual stress. The residual stress should be analyzed under this particular condition. (2) Multiple factors (e.g., eccentric swing milling parameters, lubrication conditions, tools, tool and workpiece deformation, and size effect) should be considered comprehensively when modeling instantaneous milling forces, especially for micro milling and complex surface machining. (3) The database of milling force model, including the corresponding workpiece materials, working condition, cutting tools (geometric figures and coatings), and other parameters, should be established. (4) The effect of chatter on the prediction accuracy of milling force cannot be ignored in thin-walled workpiece milling. (5) The cutting force of aviation aluminum alloy milling under the condition of minimum quantity lubrication (mql) and nanofluid mql should be predicted.

The micro/nanohardness profile has been extensively used in manufacturing to understand material properties from external surfaces to internal material. The microhardness profile requires the indentation dimension and depth measurements. Dimension measurement in most cases is interfered by noise, texture, or defects, while depth identification asks for accurate stitching of local micrographs and recognition of tilted machined surfaces. However, few commercial microhardness testers can address the issues, while the manual measurement is limited by low robustness and efficiency. To fill this gap, this paper proposes an automatic and accurate measurement method of microhardness profile based on image processing. The method can stitch local micrographs, recognize indentation dimensions and depths, generate the microhardness profile, and analyze the material property with only one click. Experiments proved the method enjoys high accuracy, automation, and robustness.

Abrasive belt grinding has been gradually applied in the precision machining of those thinner titanium-alloy components with complex surface. However, the unsatisfactory wear resistance of traditional accumulated abrasive belt becomes an obstacle to further application of this grinding technique. Therefore, the belt with a new-type structure abrasive grains is proposed, and the secondary self-sharpness performance of this hollow-sphere abrasive grain is mainly investigated in this work. Fractal dimension was employed to represent the self-sharpness of the hollow-sphere abrasive grains, and the material removal ability and efficiency was defined to represent the self-sharpness performance. It was observed that there were four damage modes of the hollow-sphere abrasive grains in the progressive wear process, and the experimental results revealed that the self-sharpness performance was optimum in condition of the damage mode c compared with others. The self-sharpness performance is improved with the augment in grinding pressure and grinding speed, but the promotion of grinding speed on which was more effective than grinding pressure. Besides, the results of contrastive experiment indicated the self-sharpness performance of hollow-sphere abrasive belt is preferable to that of traditional abrasive belt, and the maximum gap of self-sharpness performance is nearly 1.78 times. The above findings are expected to provide a fundamental research work for the further engineering application of this new-type hollow-sphere abrasive belt.

Compared with Conventional Grinding (CG), the Ultrasonic Vibration-Assisted Grinding (UVAG) is more competitive for the machining of difficult-to-cut materials. In this article, a novel ultrasonic vibration plate sonotrode that enables the special longitudinal full-wave and transverse half-wave vibration modes was proposed. The vibration characteristics of the proposed sonotrode was theoretically studied based on the apparent elasticity and Rayleigh methods, achieving a single longitudinal workpiece ultrasonic vibration with an amplitude of 7.6 μm. A superior vibration uniformity was achieved, as indicated by the coupling coefficient of 0.5. Based on the proposed method, the normal and tangential grinding forces decreased by 35 % and 39 % in comparison with the CG, and an improved machined surface was obtained in the UVAG of Ti-6Al-4V, with the following characteristics: vibration amplification of 7.6 μm; a cut depth of 0.1 mm; a workpiece feed rate of 100 mm/min; and a grinding speed of 30 m/s.

The main objective of the turboprop engine control system is to ensure propeller absorbed power at a constant propeller speed by controlling fuel flow and blade angle. Since each input variable affects the selected output variables, there exist strong interactions between different control loops of a Two-Spool TurboProp Engine (TSTPE). Inverted decoupling is used to decouple the interactions and decompose the TSTPE into two independent single-input single-output systems. The multi-variable PI controller and two single-variable PI controllers are designed for the TSTPE with actuator dynamics based on Linear Matrix Inequality (LMI), respectively, which is derived from static output feedback and pole placement condition. The step responses show that due to the difference in the response times of the selected output variables, it is difficult to design an appropriate multi-variable PI controller. The designed single-variable PI controllers are tested on the TSTPE integrated model to illustrate the effectiveness of the proposed method, that is, the interactions are first decoupled and then the controllers are designed, and the resulting simulated responses show that compared with the controller designed without actuator dynamics, the gas-generator shaft speed and power turbine shaft speed can better track their respective commands under the action of the controller designed with actuator dynamics.

This paper is focused on the nonlinear state estimation problem with finite-step correlated noises and packet loss. Firstly, by using the projection theorem repeatedly, the mean and covariance of process noise and measurement noise in the condition of measurements before the current epoch are calculated. Then, based on the Gaussian approximation recursive filter (GASF) and the prediction compensation mechanism, one-step predictor and filter with packet dropouts are derived, respectively. Based on these, a nonlinear Gaussian recursive filter is proposed. Subsequently, the numerical implementation is derived based on the cubature Kalman filter (CKF), which is suitable for general nonlinear system and with higher accuracy compared to the algorithm expanded from linear system to nonlinear system through Taylor series expansion. Finally, the strong nonlinearity model is used to show the superiority of the proposed algorithm.

In the past 20 years, the development of aluminum matrix composites (AMCs) has made a qualitative leap. This article comprehensively introduces the performance characteristics and the preparation methods of aluminum matrix composites. The powder metallurgy method (P/M) is elaborated in detail. And the applications of aluminum matrix composites in aerospace, automobile and other fields are described. Finally, the future development of aluminum matrix composites is prospected.

Collapsible loess soils are widely distributed in semiarid and arid regions. The eroded landforms formed by the unique collapsibility of loess may cause environmental damage that puts lives and pro...

In recent years, mass production of nanofiber has attracted attention of many researchers. Needleless electrospinning technology has been studied and developed to fabricate high-yield nanofibers, which could overcome the shortages of traditional single electrospinning apparatus, such as low efficiency, uneven nanofiber membrane, and difficulty in cleaning single needle. In this study, a novel needleless electrospinning apparatus was used to produce high-quality nanofiber membrane in terms of the features of small nanofiber diameter and narrow diameter distribution. Multiple jets were formed on the edge of the needleless electrospinning spinneret. The number of jets had a significant increase trend with the increase of the applied voltage. Wide-width nanofiber membrane could be fabricated by using this needleless electrospinning setup. This study also investigates the effects of process parameters on surface morphology, stress–strain, pore diameter, and filtration property of nanofiber membrane. This needleless electrospinning apparatus is suitable for industrialization production of nanofiber membrane.

Soil air permeability (ka) is an important parameter to characterize gas transport and exchange in soil. In-situ air permeability tests of loess at different depths in three sites (Xi’an, Yan’an an...

From the perspective of data science, we propose a cancer diagnosis method combining miRNA-lncRNA interaction pairs and class weight competition. First, miRNA-lncRNA interaction data is introduced into joint expression profiles, and the complex mechanism of cancer development is demonstrated in depth through the reappearance of key association information. This is an information ensemble of three carcinogenic mechanisms at dataset construction level: classical genetics, epigenetics, and the complex interaction effect between miRNAs and lncRNAs. Then, we put forward a hybrid feature selection algorithm. By preserving the interaction relationship between miRNAs and lncRNAs, it quickly and steadily removes irrelevant and redundant features and solves the high-dimensional disaster problem of cancer expression profiles. This is an information ensemble of multiple feature selection algorithms and the significant association relationship found between multi-dimensional features at feature selection level. A diversity sampling and multi-algorithm learners are used to construct a multiple heterogeneous classification models, which overcomes the small size of normal samples and the local optimum of single algorithm and single mode. This is an information ensemble of multiple classification model structures and multiple classification model state parameters at classification modeling level. At decision level, the proposed class weight which does not depend on the sample size is constructed to address the issue of unbalanced sample class of cancers. The ensemble of multi-category multi-state information at four levels (dataset construction, feature selection, classification modeling, and decision) constitutes the framework of the proposed method. We classify BRCA, LUAD and LUSC in TCGA. Compared with the state-of-the-art classification methods, the proposed method has improved classification accuracy by 9.25%~21.25%, sensitivity by 6.45%~66.45%, and specificity by 10.11%. In addition, we find that lincRNA instead of miRNA always appears in each group of feature genes, which provides a new clue for the locus target selection in cancer treatment.

In this work, a series of Cu(II)-doped Bi2WO6 nanomaterials with good photo-response properties were facile synthesized and used to obtain efficient peroxymonosulfate (PMS) activation activity for norfloxacin (NOF) removal under visible LED light irradiation. It was found that Cu–Bi2WO6 presents superior catalytic performance for NOF degradation in comparison with pristine Bi2WO6, attributed to the partial substitution of Bi3+ by Cu ions. Moreover, the effects of experimental conditions were carefully investigated, including PMS concentration, catalyst dosage and initial pH, and the experimental data fitted well with the pseudo-first-order model. Experimental results implied that there was a synergic effect of visible LED light energy and the sulfate radical (SR)-Fenton reaction. Additionally, the 5Cu–Bi2WO6 nanomaterial presented the best degradation efficiency of 89.27% and exhibited high NOF degradation in 5 cycles with limited Cu leaching. Furthermore, EPR and radical quenching experiments were performed to identify the reactive oxygen species presented in the SR-photo-Fenton reaction. Finally, the major degradation intermediates of NOF were detected, and a possible degradation pathway was given. Thus, a mechanism of the significant photocatalytic activity enhancement by copper doping of the Bi2WO6 catalyst was proposed.

The strict tolerance space of three-dimensional (3D) crystalline structures is still a significant challenge in the area of switching dielectrics in comparison with lower-dimensional structures. Generally, the function of crystalline materials can be given or adjusted by controlling the environment in which synthesis takes place or the packing rearrangement. Using this method, special functional enhancements or changes in the dielectrics can be realized by improving the synthetic strategies. Here, a 3D switchable dielectric compound [MeHdabco]K(BF4)3 was achieved by employing the temperature selective effect. In particular, its structure is completely different from the usual 3D perovskite structure, which is constructed using two different cation-template frameworks. Moreover, the 3D [MeHdabco]K(BF4)3 shows a structural phase transition at 358 K. The thermal analysis (differential scanning calorimetry (DSC)) and X-ray diffractometry results provided evidence of these phase changes. This work provides a feasible strategy that can be used to achieve the different structures of an ‘isomer’, and enrich the method used for designing diverse functional materials.

Titanium alloys is a key kind of materials in both aerospace industry and biomedical engineering. However, mechanical grinding process of Ti alloys easily leads to the featureless white layer (WL) extending tens of micrometers beneath the ground surface. Although many relevant studies have been reported so far, the WL quantification in most previous studies was performed by human raw eyes. To fill this gap, this paper proposes an image-processing-based method which can automatically recognise and measure the grinding-induced WL in the Ti alloy workpiece. By comparing the results separately obtained by the proposed method and manual measurement, it shows that the method can recognise and measure the WL region accurately (the maximum absolute error of 0.09 μm) and quickly (1.65 s per micrograph). More importantly, the method does not require any parameter presetting and has good robustness in terms of (i) varied WL region thicknesses, (ii) different workpiece placements and (iii) the interference from the noise pixels. The method therefore is believed to be not only meaningful and helpful to automatically measure the WL thickness in Ti alloys in large quantities, but also transferable to other industrial applications.

Metal matrix composites (MMCs), as advanced substitutes of monolithic metallic materials, are currently getting an increasing trend of research focus as well as industrial applications for demanding applications such as aerospace, nuclear and automotive because of their enhanced mechanical properties and relative lightweight. Nevertheless, machining of MMC materials remains a challenging task as a result of their structural heterogeneity which leads to deterioration of the machined surface integrity and rapid tool wear. While most of the research was focused on testing and analytical/numerical investigations of the tool wear, limited work was focused on machined surface integrity of MMCs. This paper presents a detailed literature survey on the conventional and non-conventional machining of metal matrix composites with the primary focus on the aspects related to workpiece surface integrity. The contribution of material mechanical and microstructural properties as well as the material removal mechanism upon the quality of workpiece surfaces/subsurface are discussed along with their influences on the fatigue performance of machined part.

Fixed-abrasive planetary lapping process can be considered as one of the most widely-used finishing technologies to produce high-quality surfaces. However, most of the previous studies (i) neither considered the eccentricity between the pad rotation and the workpiece revolution, (ii) nor provided the full-time process details. More importantly, most of the previous models were unable to accurately quantify the periodic cycle duration. To fill this gap, this paper proposed the generic analytical model of the periodicity in the fixed-abrasive planetary lapping process. The model can calculate key lapping details in both the time and spatial domains (e.g. cycle duration, effective trajectory number, and lapping mark pattern), which were then compared and validated by the experimental trials. Based on the validated model, the effect of each lapping parameter on the periodicity was discussed for the first time. The proposed model and key findings in this study are anticipated to be not only meaningful to lay the theoretical foundation of lapping technology, but also useful to provide the practical guidance for both lapping parameter optimisation and lapping pad design in the industrial manufacturing sector.

An equivalent circuit model of double hexagonal loops frequency selective surface (FSS) was established. The formulas of LC parameters were proposed with equivalent repetition period. The reflection frequency, transmission frequency, and the location of first modal interaction null were simulated, and the results showed a good agreement in full-wave simulation result. On this basis, an ultra-wideband composite absorbing material (CAM) was proposed, and its equivalent circuit model was also established. A sample was fabricated and measured to verify the validity of the model. The results showed a good ultra-wideband absorbing performance in the range of 1.9–8.9 GHz.

PAN hollow fiber functional membrane with heavy metal ion adsorption capacity was prepared via layer-by-layer method using diazo-resin (DR). Ethylenediaminetetraacetic acid (EDTA) and graph...

The need of carbon fiber–reinforced plastics (CFRP) has been driven by the increasingly wide applications in many industrials including sports, transportation, and energy. However, until now, the poor machinability of CFRP can be still considered the key problem and the most urgent machining-induced issue can be the delamination damage in the drilling process. Although many efforts have been paid to investigate this topic, most of them investigated the delamination at either the hole entrance and the exit. Very few of these studies focused on the internal delamination defects on the hole wall, although these internal defects can be as important as the entrance and exit defects. To fill this gap, this paper investigated the condition effects (feed rate, spindle speed, ultrasonic vibration of drills, and the workpiece support strategy) on the delamination in CFRP drilling, with the special focus on the internal delamination damage on the inside hole walls. Based on both the experimental and theoretical analysis, the effectiveness of the back supports and the variable feed rates was investigated as well. Considering few published studies reported the delamination on the hole wall, the key findings in this paper are expected to be meaningful to deepen the understanding of CFRP drilling and helpful to provide some industrial guidance.

Modeling of grinding process, especially the grinding forces, has been studied extensively. Most previous work concerns the conventional grinding process using a rigid wheel, where the forces are generally based on the preset depth of grinding. However, for compliant grinding such as Shape Adaptive Grinding (SAG) that adopts an elastic tool covered with abrasive pellets, the penetration depth of individual abrasive grains is not simply equal to the preset value. As elastic contact occurs between the tool and workpiece, previous models are not able to estimate the material removal mechanism. Besides, the progressive transitions in grain-workpiece interaction for compliant cutting tools have not been reported yet. To fill these gaps and to offer a fundamental understanding of the compliant grinding process, we propose in this study a new multi-scale model spanning from macroscopic tool-workpiece contact to microscopic grain-workpiece interaction in the unique conditions of using a compliant grinding tool, i.e. SAG tool. Based on the spring-grain model and considering the stochastic nature of grain size and wear flat area, the static penetration and dynamic removal of individual grain can be predicted. Particularly, the removal mechanism is clarified with a new consideration of the transition between rubbing, plowing and cutting stages for each individual grain of the compliant tool. Experiments including scratch tests and removal footprints were carried out, and the high consistency with theoretical predictions validates the proposed model. Finally, considering the progressive abrasive wear in grinding, in-process wear compensation was conducted to enable consistent material removal on aspheric steel molds. The proposed method is not only meaningful to reveal the mechanism of SAG process, but also offers a new foundation for studying other compliant grinding processes in future.

Thanks to the superior machined surface integrity, high machining feasibility, and limited tool wear, the Abrasive Air Jet Polishing (AAJP) has been considered as a widely used finishing process, especially for high-valued small and complex optics products. Therefore, many experimental, theoretical and processing technology studies have focused on this topic. However, experimental studies cannot provide an in-depth understanding of the process principle while most of the theoretical models/methods have been established based on many unrealistic assumptions. To fill this gap, this paper suggests an analytical model of the polished surface topography (or footprint) considering (i) the horizontally asymmetric cross-section profiles of a single-abrasive impact footprint, (ii) the abrasive-workpiece elastic deformation and further springback when the abrasive bounces back, and (iii) the overlapping footprints generated by multiple abrasives having a normal-distributed size. The systematic validation trials proved the model accuracy and feasibility. Based on the validated model, the effects of the polishing parameters including the jet pressure, jet angle, and abrasive size on both machined surface roughness and removed material volume are studied. The proposed model is anticipated for not only exploring and laying the theoretical foundation of the AAJP process in more depth, but also to provide guidance for industrial manufacturing in terms of polishing parameter optimization and polished surface prediction.

Membraneless microfluidic fuel cells are miniaturized and integratable power sources as compared with conventional fuel cells based on membrane electrode assembly. To elucidate the interaction of two-phase flow, mass transport and electrochemical reactions, a two-dimensional two-phase model is developed for the microfluidic fuel cell with a flow-through porous anode. The two-phase flow in the anode and the microchannel is formulated by the two-fluid model and mixture multiphase flow theory, respectively. The modelling results suggest that the retention of gas phase in the anode catalyst layer and microchannel can reduce the effective active area and impede the proton conduction to limit the cell performance. However, the commonly used single-phase assumption fails to capture these effects, resulting in overestimated performance. The fuel crossover shows an opposite trend as compared with that predicted by the previous single-phase model, and is found to correlate with the two-phase flow in the microchannel. The flow rates of fuel and electrolyte on the fuel transport and gas-phase removal are also discussed. The present work highlights the significance of two-phase effects in the modelling of microfluidic fuel cells, and provides insights into the two-phase flow and mass transfer for future development and operation.

Abrasive Air Jet Polishing (AAJP) process can be considered as one of the most promising ultra-high-precision finishing methods of quartz glass products due to the superior machined surface integrity, and the high machining feasibility for free-form surfaces. Although many academic and engineering efforts have been paid so far to AAJP process from the theoretical, numerical and experimental aspects, most of the available studies have considered neither (i) the stochastic nature of the abrasive sizes nor (ii) the elastic springback after the impacting abrasives bounced back from the workpiece surface. To fill this gap, this paper proposes the predictive model of the machined surface topography in the AAJP process of quartz glass. A series of experimental trials are performed as well which to a large extent proved the model feasibility and accuracy, and, more importantly, the necessity to consider the normally-distributed abrasive sizes, the stochastic abrasive distribution within the spray airflow, and the elastic workpiece deformation recovery after the AAJP process. Both the experimental and theoretical results also conclude that the small-sized abrasives and the low jet airflow pressure were more effective to achieve the smooth surfaces. The proposed model in this work is expected to be not only helpful to provide the theoretical foundation to study more in-depth mechanism of the AAJP process of brittle materials, but also meaningful to guide the industrial manufacturing in terms of machining parameter optimisation and machined surface quality prediction.

Janus membranes (JMs) with opposite wettability have brought about new opportunities to tackle the challenging issues encountered in oil/water separation. However, these achievements suffer from empirical availability for the separation of oil-in-water emulsions, lacking a controllable way to tune the synergistic effect of asymmetric configurations, which is the “inner” driving force for practical performance. Herein, the role of the asymmetric configuration is theoretically and experimentally demonstrated in the Janus structural design, membrane fabrication, and separation performance for oil-in-water emulsions. These significant insights are particularly gained by analyzing Young–Laplace capillary pressures, measuring the adhesive forces between the oil and membrane surface, and monitoring the demulsification and oil transportation processes. Fluorescence imaging has been used to in situ visualize the separation process and then a mechanism is firstly proposed as demulsification followed by rapid unidirectional oil transportation for surfactant-stabilized oil-in-water emulsions. The two successive processes are strongly governed by the controllable asymmetric configuration of the JMs. An efficient oil separation can, therefore, be achieved from surfactant-stabilized oil-in-water emulsions with a wide size distribution (from nanometers to microns) by optimizing these two stages via tuning the hydrophilic/hydrophobic configuration and surface charge property of the JMs. Therefore, this work is expected to yield a design principle and guideline for developing JMs with applicability in the practical separation of oil-in-water emulsions.

This paper presents a beamforming microwave-induced thermoacoustic (TA) imaging system for screening applications. Near-field/quasi-near-field beamforming with multiple applicators focuses the radio-frequency (RF) energy to the target location in depth and enhances the TA signal generation, thereby lowering the peak-power requirements of the solid-state RF power amplifier (PA). More importantly, the proposed beamforming method reduces surface heating at the skin interface by distributing the excitation power over multiple sites and, hence, reducing the per-element peak at a similar acoustic signal-to-noise ratio (SNR). A 3-D printed setup in a conformal configuration is designed and used to demonstrate signal enhancement with RF focusing. By tuning the phase of each channel, the system can focus RF energy to specific locations and steer the focal point location across the region of interest. With a four-element array, measurements confirm a 15.8-dB acoustic intensity SNR improvement compared with a single power-limited excitation and 3.8-dB improvement compared to a PA with the same total peak power (i.e., $4\times P_{\text {out}}$ ). The results herein suggest the potential benefits of the proposed beamforming system and imply further enhancements once scaled to a larger array.

Considering the nonlocal theory and the flexoelectric effect combined with Euler-Bernoulli beam model, Hamilton principle is generally used for deriving the governing equation, then the corresponding analytical solution of the deflection is solved, and the differential quadrature method can be applied effectively here to deduce the dimensionless natural frequency of vibration. The static and dynamic responses of piezoelectric nanobeams which taking the flexoelectric effect into account are studied. The conclusions present that how deflection, dimensionless natural frequency and axial motion stability vary as a function of flexoelectric effect, nonlocal parameter, piezoelectric effect, temperature, voltage and axial velocity.

This paper investigates the vibration behaviors of a rotating functionally graded piezoelectric nanobeam based on the nonlocal strain gradient theory and Reddy beam model. Firstly, the differential equations of motion are obtained by the energy variation. The numerical method is used to transform derived partial differential equations into algebraic equations. Subsequently, the natural frequencies values are obtained of the nanobeam by solving the eigenvalues of the matrix. The influence of rotational velocity, nonlocal parameter, the strain gradient parameter and voltage on the natural frequencies are analyzed. Finally, the results show that the effects of nonlocal parameters on the vibtation frequencies of nanobeams is related to the ratio of the nonlocal parameter and the strain gradient parameter. This further illustrates the rationality of using two small scale parameters to study nanomachenics. Additionally, the changes in value of rotational velocity and voltage will change the natural frequencies. The research results of this paper may play an important guiding significance for the design of micro-nano rotating machinery and related mechanical research.

In this work, combined the classical plate model and nonlocal elasticity theory, the natural frequencies of flexoelectric nanoplates are studied. Firstly, by the Hamilton’s principle, the motional differential equations and boundary conditions of the flexoelectric nanoplates are obtained. Then the differential equations and mechanical boundaries have been solved with the differential quadrature method. After this, the Navier’s analytical solutions of nanoplates’ natural frequencies with four simply supported edges are calculated. The numerical solutions of the natural frequencies are similar to the analytical solutions, which verifies the correctness of the differential quadrature method. Ultimately, the influences of nonlocal parameters, length-height ratio size and flexoelectric coefficient on the natural frequencies of the nanoplates are discussed by numerical calculation results.

Loess is an unsaturated soil and is widely distributed in arid and semi-arid areas in northwest China. Air permeability is a key parameter for determining the permeation performance of unsaturated soil. At present, the air permeability of loess is mostly determined by laboratory measurements with few studies using in situ measurements. In this paper, an improved loess air permeameter was used to measure the air permeability of in situ loess and undisturbed loess samples in three typical loess regions. The in situ air permeability measurement results obtained with the improved air permeameter were compared with laboratory (in-lab) permeameter measurements of undisturbed loess samples since the in-lab-based method is relatively mature. Experiments were conducted to investigate the influence of the void ratio, the water content and other parameters of the eroded loess formation on the air permeability of the in situ loess samples. The results showed that the in situ air permeability measurements obtained from the improved air permeameter are highly reliable. The air permeability of loess in different regions was highly correlated with the particle size distribution. The higher the clay content, the lower the number of effective permeation pores and the lower the air permeability of the loess. Increasing depth is positively associated with the water content and the dry density, but negatively related to the void ratio and air permeability. The air permeability was the highest near sinkholes, fissures, and trenches; it initially decreased with increasing distance from these features and stabilized eventually. The results of this study successfully provide technical information and support for engineering applications in loess areas.

This paper takes copper as the research object, aiming to study the influence of waveguide surfaces roughness and the thickness of the metal surface oxide layer on the Passive Intermodulation (PIM) powered. Starting with the change in shrinkage resistance caused by the deformation of the micro-convex body, two-dimensional and three-dimensional fractal geometric rough surface mathematical models through the W-M function are established. Moreover, the influence of fractal dimensions on the rough surface is analyzed. Then through the Metal-Medium-Metal structure formed by the waveguide connection, the equivalent circuit model is established, and the third-order PIM power is calculated. The results show that the PIM becomes more serious as the roughness of the contact surface increases, and the thickness of the oxide layer on the contact surface increases.

Objectives The current study was focused on preparing curcumin (CUR) supersaturated self-nano-emulsion (PI-CUR-SNEDDS) using hydrophilic polymer and to study the influence of polymer precipitation inhibitor on the physicochemical and biopharmaceutical properties of the PI-CUR-SNEDDS. Methods PI-CUR-SNEDDS were prepared using hydrophilic polymer in order to maintain the supersaturation of CUR in nano-emulsion solution, artificial gastrointestinal fluid (AGF), and the precipitates formed, and characterised by in vitro dispersion tests, in vitro intestinal absorption and in vivo pharmacokinetic and compared with CUR-SNEDDS. Key findings PI-CUR-SNEDDS prepared with 2% hydroxypropyl methylcellulose 55–60 (HPMC55-60) as precipitation inhibitor (PI) significantly improved the viscosity, physical stability and CUR’s equilibrium solubility of nanoemulsion. HPMC55-60 and CUR interact in AGF through intermolecular interactions, form hydrogen bonds, and produce amorphous precipitates. Compared with CUR-SNEDDS, the proportion of CUR in the hydrophilic phase increased by about 3-fold, and apparent permeability coefficient (Papp) in duodenum, jejunum, ileum, and colon increased by 2.30, 3.65, 1.54 and 2.08-fold, respectively, and the area under the plasma concentration-time curve0-12h of PI-CUR-SNEDDS also increased by 3.50-fold. Conclusions Our results suggested that HPMC55-60 maintained the CUR supersaturation state by forming hydrogen bonds with CUR, increasing the solution’s viscosity and drug solubilisation, thus improving the absorption and bioavailability of CUR.

This study aims to investigate the relationship between key physicochemical parameters related to composting process and bioavailability of Cd, As and Cr during swine manure composting through regulating different initial carbon to nitrogen (C/N) ratios (15:1, 20:1, 25:1) and bulking agent types (straw, green waste). Results showed that higher initial C/N ratio of 20:1 or 25:1 and straw as bulking agent were optimal to reduce the bioavailability of Cd, As and Cr (62.4%, 20.6% and 32.2% reduction, respectively). Redundancy analysis implied that the bioavailability of Cd was significantly associated with total phosphorus and total nitrogen, deducing the formation of phosphate precipitation and biosorption might participated in the reaction process, while that of As and Cr were mainly influenced by organic matter (OM), cation exchange capacity (CEC) and OM, CEC, electric conductivity, respectively. A total of 48.5%, 64.6% and 62.2% of Cd, As and Cr redistribution information could be explained by the above parameters. Further correlation analysis revealed that bioavailable As and Cr were negatively correlated with humic acid to fulvic acid ratio. In summary, this study confirms that the mechanisms of phosphate precipitation, biosorption and humification played critical role in reducing Cd, As and Cr bioavailability during swine manure composting.

s: In order to investigate the influence of curved sidewall on the maximum temperature and the longitudinal temperature distribution induced by linear fire source in utility tunnel, a sequence of experiments was conducted in a reduced-scale utility tunnel, whose fire source is placed at d (0, 10, 20, 30, 40, 50, 60 cm) away from the centerline. The result is as follows: (1) In order to represent the effect of portal-sealed sidewall and curved sidewall, a dimensionless correction coefficient λ and the modified effective height of the ceiling Hef′ are employed, respectively. Besides, a dimensionless empirical formula was proposed as (Eq. 13) to predict the average maximum temperature rise of plume impingement zone beneath the ceiling centerline induced by linear fire source in utility tunnel, which is related to d. (2) It is found that longitudinal temperature beneath the ceiling centerline could be divided into two zones: plume impingement zone and temperature decay zone. The temperature of the plume impingement zone is basically the same, while the temperature of the decay zone falls exponentially. An empirical formula based on experimental data was presented as (Eq. 15). Keywords: Utility tunnel, Linear fire source, Maximum temperature, Longitudinal temperature distribution

Online forums in Chinese universities play an important role in understanding collective behavior of college students. Of particular interest are community and popularity. We address these two issues by examining data from Bulletin Board Systems (BBSs) of four Chinese universities. To characterize users' behavior, we introduce a hypothesis test to infer individual preferred boards, which yields a polarization of users. We also perform a multilevel algorithm to detect communities of each BBS network. We measure the similarity between the board-preferred polarization and the algorithmically identified community structure by quantitative and visual tools. The resulting discrepancy indicates that board labels are inadequate to represent underlying communities. To reveal online popularity, we employ latent Dirichlet allocation to mine topics from threads to compare popularity in different universities. Based on which, we implement the Cox-Stuart test to explore the change in popularity over time and reproduce significantly ascending and descending topics around a decade. Finally, we devise a two-step model based on users' preference and interests to reproduce the observed connectivity patterns.

Membraneless microfluidic fuel cells (MMFCs) outperform traditional membrane-based micro-fuel cells in membraneless architecture and high surface-to-volume ratio and facile integration, but still need substantial improvement in performance. The fundamental challenges are dictated by multiphysics regarding cell configurations: the interaction of fluid flow, mass transport and electrochemical reactions. We present a numerical research that investigates the effect of geometrical configurations (rod arrangement, cell length, rod diameter and spacer configuration) on the fuel transport and performance of an alkaline MMFC with cylinder anodes. Modeling results suggest that the staggered rod arrangement outperforms the in-line case by 10.1% at 50 μL min–1. Cell power output and power density vary nearly linearly with the cell length. In the case with 0.7 mm anodes and 0.3 mm spacers, the increased flow resistance at anode region drives the fuel to intrude into the spacer zone, leading to fuel transport limitation at downstream. The feasibility of non-spacer configuration is demonstrated, and the power density is 93.7% higher than the baseline due to reduced cell volume and enhanced fuel transport. In addition, horizontal extension of the anode array is found to be more favorable for scale-up, the maximum power density of 181.9 mW cm–3 is predicted. This study provides insight into the fundamental, and offers guidance to improve the cell design for promoting performance and facilitating system integration.

DD6 nickel-based single-crystal superalloy has been treated as an ideal material for the high-valued and high-performed aero-engine components; however, it was found difficult to remove material from the DD6 nickel-based single-crystal superalloy in cutting and grinding. Although creep-feed deep grinding (CFDG) has been widely employed for various nickel-based superalloys (i.e., Inconel 718, DZ4, IN738LC), very few efforts however have been focused on the nickel-based single-crystal superalloy. With this, this paper focuses on CFDG of DD6 nickel-based single-crystal superalloy to gain the more in-depth understandings, targeting grinding force, specific grinding energy, grinding temperature, surface integrity, and wheel wear condition. Scheduled experimental observation proved that (i) microcrystalline alumina abrasive wheel generally shows more superior grinding performances in aspect to grinding force, force ratio, and specific grinding energy than that of brown alumina abrasive wheel; (ii) grinding temperature is decreased by 35% by using the microcrystalline alumina abrasive wheel compared to brown alumina abrasive wheel, and therefore the microcrystalline alumina abrasive wheels have the potential to be applied in the high-efficiency grinding; (iii) the surface ground by the microcrystalline alumina abrasive wheel is found smooth without any grinding-induced damage; and (iv) microcrystalline alumina abrasive wheels easily lead to micro-fractures and therefore result in better self-sharpness ability and longer service life in CFDG of DD6 nickel-based single-crystal superalloy.

The combined influence of Mg and Ca treatment on the properties of heat-affected zone (HAZ) of low-carbon steel after high heat input welding was systematically studied. Experimental steels deoxidized with different elements were prepared, i.e., C–Mn steel with Al, Ti–Ca steel with Ti and Ca, Ti–Mg–Ca steel with Ti, Mg and Ca. Results showed that the inclusions in C–Mn steel were mainly Al2O3 and MnS with low density and large size. However, the average size was refined to only ~ 0.34 μm in Ti–Mg–Ca steel and the amount increased remarkably. Microstructure of simulated HAZ for 200 kJ/cm changed from ferrite side plates or upper bainite to acicular ferrite after treatment with Ti, Mg and Ca. Ca addition decreased the strain field around inclusions and enhanced the ability of acicular ferrite nucleation. In situ observation of Ti–Mg–Ca steel showed that the movement of austenite grain boundaries was retarded and nucleation sites of acicular ferrite were greater than Ti–Ca steel because of Mg addition. Impact energy of HAZ at − 40 °C was increased from 7 to 232 J and showed excellent stability because of Ti–Mg–Ca treatment. High volume fraction of acicular ferrite acted as obstacles toward cleavage cracks.

As an important advanced decoration material, glass-ceramics has attracted much attention. By means of XRD, SEM and mechanical properties tests, this research studied the sintering and crystallizat...

Grinding process of optical glass has been reported to be related with the creation of subsurface cracks. However, for the time being, most measurement methods have been depended on human operations. In this paper, an intelligent assessment method based on image processing technique is proposed. Grinding trials proved that, the proposed method can accurately (with the biggest relative error of 3.53%) and quickly (nearly 1.6 seconds per micrographs) recognize and measure the subsurface crack depths. More importantly, the proposed method has good robustness to different-sized images. Besides, the method does not require any input parameters or any adjustment of thresholds, therefore the method does not require any prior knowledge of either mechanical grinding process or brittle material behaviors relating with subsurface cracks. Based on above, the proposed method is expected to be meaningful to both metrology equipment companies and optical glass manufacturers.

Occupant safety evacuation in fires is a critical issue in public safety field. The evacuation process is divided into several stages and each stage can be influenced by various uncertain factors. Some factors were studied in this paper based on the Monte Carlo approach. The safety level affected by different factors and the sensitivity of sampling size were analysed according to the failure probability model of occupant evacuation. The results show that safety level of occupant evacuation in buildings can be evaluated by the failure probability model. When the population density is more than 0.8 pers/m2, the failure probability goes up rapidly with the fire growth rate increasing. Whether the fire is large or not, the population density have a great impact on the evacuation. Then the influencing degree on failure probability of different parameters are changeable in various conditions. In addition, when the sample capacity is large enough, the Monte Carlo simulation can be deemed accurate.

Optical glass K9 is a critical kind of optical materials, however experiments have indicated that the mechanical grinding of K9 easily led to subsurface damage (SSD). Although substantial SSD measurement methods have been suggested, the problems including the prior knowledge of SSD and slow measurement speed still impede the reported method applications. To this end, this paper has presented an image-process-based method that can identify and measure the grinding-induced SSD in K9 specimens. By performing grinding trials, the method has been found to be able to accurately (with biggest relative error of 3.13% in comparison with the manually measured results) and quickly (with the measurement speed of 1.68 s per image) measure SSD depths. Without any parameter presetting, the method enables automatic SSD measurements, allowing the users without SSD knowledge to be able to use the method. Moreover, the method has shown the good robustness to the input image size, illumination, tilted specimen placement, and material flaws. The method is therefore anticipated to be meaningful for the industrial manufacturing, design and application of optical glass.

Machining efficiency could be increased and chatter vibrations could be suppressed by employing irregular pitch angles onto milling cutters. Applying variable pitch cutters could improve machining stability by disrupting the regenerative chatter mechanism and reducing cutting forces due to decreased nonlinear dynamic chip thicknesses. Previous studies on variable pitch cutters have been mainly on investigating vibration suppression and dynamic modelling. There is a lack of efficient and practical variable pitch cutter design methods for practical industrial applications. An analytical method for designing milling cutters with alternating variable pitches has been proposed in this paper. In this method, a new variable, the generic sum of phase difference between the inner and outer waves, has been defined to model the machining dynamics and stability of the variable pitch cutter. The phase difference value has then been investigated to obtain its generic optimal solution to the stability limit considering different cutting conditions. Based on this, the analytical variable pitch cutter design method is derived. The experimental results have manifested that, compared with uniform pitch cutter, the variable pitch cutter, designed using the proposed method, was able to achieve 1) a critical stable axial depth of cut improvement of 126% under the desired spindle speed, 2) a cutting force reduction of 53%, 3) a decrease of 75% and 52% in Sq (the root mean square length of the scale limited surface) and Sz (the maximum height of the scale limited surface) of the machined surfaces respectively. These significant improvements approved the superiority and robustness of the proposed design method for chatter suppression and may promote the application of variable pitch cutter technologies.

Textured Abrasive Tool (TAT) offers an effective solution to alleviate thermal issues during machining processes, and laser machining has been identified as one of the most promising fabrication approaches. Laser ablation of TATs has unique process complexity thanks to not only the porous structure of abrasive tools but also the bond-abrasive multiple-material nature. Due to this complexity, most previous investigations on laser-based generation of TATs relied on the single-pass ablation strategy, and therefore most reported TATs had still 2D structures with the same ablation depth. Although the creation of depth-controlled 3D structures based on multiple-pass laser ablation strategy has been investigated in the laser machining community, few attempt applied this technique to TAT fabrication, and this paper aims to fill this gap. Special attentions were paid to the effect of both laser pass numbers and scanning speeds on the ablated structure shapes, depths, widths, and morphologies. The experimental results were well supported by the theoretical explanations, based on which the pragmatic laser parameter selection strategy was proposed. With the strategy, we successfully produced one TAT having 2D sinusoidal profiles and one with 3D staggered hemisphere micro-structures. Grinding trials were performed as well to prove the superior performances of the produced tool. This work might provide important reference for designing and manufacturing the next-generation advanced abrasive tools embedded with complex and functional 3D machining elements.