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Locust powder was converted into water-soluble fluorescent nitrogen-doped carbon dots (N-CDs) with gram-scale yield through a self-exothermic reaction between nitric acid and diethylenetriamine (DETA) within 10 min. The morphology, elemental information, and optical properties of the N-CDs were characterized using high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and Fourier-transform infrared, ultraviolet-visible and fluorescence spectroscopy. Spectroscopic investigation indicated that the fluorescence emission behaviour of N-CDs is excitation wavelength dependent, with the strongest emission peak at 470 nm using a 390 nm excitation wavelength. The strong absorption peak of sunset yellow (SY) at 482 nm overlaps substantially with the blue emission peak (470 nm) of N-CDs. This enables the fluorescence emission of N-CDs to be obviously quenched by SY through the inner filter effect. There was a good linear relationship between the fluorescence quenching degree and the concentrations of SY within the range 0.5-40 μM. The detection limit of developed fluorescence assay for SY is 28 nM, and the relative standard deviation is 2.3% (c = 10 μM). The N-CDs derived from locusts by the self-exothermic reaction are highly selective and sensitive fluorescent probes for SY, which were applied to the fluorescence sensing of SY in different food samples with satisfactory results.

In the present study, the fiber-bending around the needle during the piercing process of the carbon fabric is investigated. In this regard, a mathematical model is established to investigate the bending elongation of the carbon fiber around the needle and the interaction between the carbon fiber and the needle tip. Then the mechanical behavior of the carbon fabric when moving down the tip of the steel needle is analyzed. Based on the performed analysis, a shape curve equation that satisfies the puncture needle tip is established. Furthermore, the influence of different needle tip shapes on the mechanical behavior of the carbon fiber is analyzed. The performance of the needle tip is subjected to different loads, including the puncture template, horizontal tension of the fiber to the needle tip, frictional resistance between the fiber and the needle tip, sliding force, and the bending moment. The performed analysis shows that when the shape of the needle tip assumes the form of curve 10, the downward force, horizontal tension, friction resistance, sliding force, and bending moment are minimized. Accordingly, curve 10 is proposed as the optimal shape for the needle tip. The present study is expected to provide theoretical guidance for selecting overall puncture process parameters.

In order to investigate further the compaction characteristics of the three-dimensional four-direction preform of carbon/carbon composite, a model of three-dimensional four-direction numerical preform at the micro-scale was established using the programming language in Python based on the ABAQUS simulation platform more realistically to reflect the micro-structure of the preform. A model of three-dimensional fiber numerical growth was built to describe the changes of fiber bundle cross-section under compressive load considering the random distribution, deflection, bending and the physical characteristics of fibers not penetrating each other in three-dimensional space. In addition to exploring the characteristics of the fiber bundle compaction process in the inter-laminar dimension, the interaction between laminated fibers of the preform was analyzed; the method of finite element was employed to construct a compaction model of the three-dimensional four-direction preform; the deformation of inter-laminar fibers under compressive load was studied by the numerical simulation method; the nonlinear mapping relationship between compressive load and compaction height consistent with the preform compaction experiment was obtained. The results demonstrated that the deflection coefficient of the numerical model was 0.32, which was most consistent with the actual result.

Metal organic frameworks (MOFs) are a new type of porous materials with some unique characteristics such as uniform pore size, adjustable pore structure, easy synthesis and structural diversity. Ionic liquids-modified MOFs (ILs/MOFs) composite materials not only retain the structural characteristics of MOFs, but also have the advantages of adjustable physical and chemical properties of ILs with high stability. They have great application potential in the field of separation and analysis, which has aroused great interest of researchers. This article mainly reviews the preparation methods of ILs/MOFs composite materials and their research progress in separation and analysis in the latest five years, including adsorption/extraction, chromatographic separation, spectral and electrochemical analysis. And their future development trends are expected.

Recent research has shown that, during integrated piercing, the yarn tension can displace the needles from the centers of the holes in the piercing template. To reduce the damage done to the needle tips when the needles and the hole walls collide when the needle displacement is too large, this paper proposes a method for optimizing the needle shape that satisfies the strength constraint while targeting minimum needle displacement. First, the optimal objective function and strength constraint conditions for the tip displacement of the integrated puncture needle are established, which are affected by many factors. Then, the feature selection method of machine learning is used to reduce the dimensionality of the objective function after data reduction, and the feasible region of key features is reduced to avoid falling into the local best point in the optimization iteration. Finally, machine vision is used to measure experimentally the tip displacement of a needle array. The results show that the average tip displacement is reduced by 18.16–31.42% and the collision risk is reduced from 43.14% to 5.54%. It shows that the optimization method of needle shape based on feature selection is effective for reducing needle tip impact damage during integrated piercing.

In this work, poly(sodium 4-styrenesulfonate) (PSS) modified molybdenum disulfide quantum dots (MoS2-PSS QDs) were synthesized via a simple hydrothermal method using l-cysteine and anhydrous sodium molybdate as precursors and PSS as a modification reagent, and a selective and sensitive fluorescent sensing method for the determination of p-nitrophenol (p-NP) based on their UV emission was developed. The obtained MoS2-PSS QDs have an obvious UV emission peak (390 nm) with quantum yield of 5.13%. The strong absorption peak of p-NP at 400 nm has large spectral overlap with the UV emission peak (390 nm) of MoS2-PSS QDs. Because of this p-NP absorption, the fluorescence of MoS2-PSS QDs at 390 nm is quenched with the introduction of p-NP via the inner filter effect (IFE) and the decreased fluorescence intensity was linearly proportional to the p-NP concentration in the range of 1–20 μmol/L, leading to a detection limit of 0.13 μmol/L for p-NP. The MoS2 QDs-based fluorescent probe for p-NP is sensitive and selective and was successfully applied in the determination of p-NP in the pond water samples with satisfactory results.

In this work, cis and trans fatty acid (FA) contents in edible oils was determined using 1H nuclear magnetic resonance (1H NMR) spectroscopy. The comparison of 1H NMR spectra of edible oil and cis-trans isomerized oil showed that they were different in three regions: (1) 2.880 - 2.650 ppm caused by bis-allylic protons; (2) 2.140 - 1.900 ppm due to allylic protons; and (3) 1.030 - 0.930 ppm due to methyl protons of linolenic acyl groups. The 1H NMR signals in these regions were combined with partial least squares method to predict contents of cis/trans fatty acids in edible oils. The results showed that the predicted values were consistent with the gas chromatography-measured values and had a good linear relationship with a correlation coefficient (R2) of above 0.98. This work demonstrates that 1H NMR spectroscopy was successfully used to determine the composition of both cis and trans fatty acids in edible oils.

In this work, a simple and effective strategy for designing a ratiometric fluorescent nanosensor was described. A carbon dots (CDs) based dual-emission nanosensor for nitrite was prepared by coating the CDs on to dye-doped silica nanoparticles. Dual-emission silica nanoparticles fluorescence was quenched in sulfuric acid using potassium bromate (KBrO3). The nitrite present catalyzed the KBrO3 oxidation, resulting in ratiometric fluorescence response of the dual-emission silica nanoparticles. Several important parameters affecting the performance of the nanosensor were investigated. Under optimized conditions, the limit of detection was 1.0 ng mL−1 and the linear range 10–160 ng mL−1. Furthermore, the sensor was suitable for nitrite determination in different food samples.

Asphalt mixture is a typical viscoelastic material. Its mechanical response and deformation behavior depend on the role of time, temperature conditions and stress levels. Three kinds of asphalt mixture (i.e. AC-13, AC-16, AC-20) were used for the static creep test in different temperature conditions and stress levels. According to the creep curve, The Burgers viscoelastic parameters including E1, η1, E2, η2 and the steady-state creep rate K were obtained. The effects of test temperature, stress level and aggregate gradation on the viscoelastic parameters of asphalt mixture were analyzed. Based on the relationship between the steady-state creep rate and the experimental temperature & load stress, the stress index and creep activation energy of asphalt mixture were proposed. By analyzing the relationship between the creep activation energy and the rutting depth, the creep mechanism of the asphalt mixture was discussed. The results show that with the increase of temperature, the four parameters of E1, η1, E2 and η2 of the three kinds of asphalt mixtures generally decrease. But at different temperatures, the viscoelastic parameters of these three kinds of mixtures are not the same. The stress level has a significant effect on the viscoelastic properties of the asphalt mixture. The four viscoelastic parameters have the largest differences when the stress level is at the intermediate load level of 0.5 MPa, but the responses of the different gradation asphalt mixture to the stress level are different. With the increase of temperature and load stress, the steady-state creep rate increases gradually, but the stress indexes of these three kinds of asphalt mixtures stress index are not different. All of them are less than 3, and belong to the diffusion creep under the control of aggregate interface dislocation mechanism. The asphalt mixture that has larger creep activation energy has better stability under high temperature. AC-16 mixture has the highest creep activation energy. Nominal particle size is not a decisive factor for the performance in high temperature.

The preparation of crumb rubber modified asphalt (RA) shall effectively recycle waste rubber and abate environmental contamination. To ascertain the composition and the factors affecting the viscosity of RA, some samples were prepared in the case of different conditions of mixing temperature and processing time for different rubber dosage and rubber size. Brookfield viscosity tests were conducted on RA samples, and the impact exerted by these factors on viscosity of RA was anatomized. The visco-flow activation energy (Eη) of RA was acquired through adopting Arrhenius equation in line with the viscosity values of asphalt in the case of different temperatures. The changing regularity of Eη was anatomized. The viscosity of rubber asphalt can be split into three parts: the contribution of base asphalt (BE), rubber and asphalt interaction effect (IE) and crumb rubber particle effect (PE), and additionally the viscosity definition is proposed as η R A = η 0 ( 1 + IE + PE ) . To isolate the PE, the sieving test was designed. Rotary viscosity tests were conducted on RA samples and asphalt samples separated from crumb rubber through adopting Brookfield viscosity meter. The impact exerted by these factors on the viscosity composition parameters IE and PE of rubber asphalt was anatomized. In line with the viscosity definition, the viscosity prediction model of rubber asphalt was established. It is indicated from the results and analysis that the viscosity values of RA increase by the exponential growth model continuously with the increase of rubber content. There is a certain equivalence for rubber asphalt viscosity between raising mixing temperature and extending the processing time. But too high temperature or excessive time may result in excessive degradation of rubber molecules, which shall cause the decrease of RA viscosity. With the rising of the dosage of crumb rubber, Eη of RA for origin or aged samples both goes up first and thereupon drops down. And peak Eη exists in the range of rubber content from 10% to 15%. The Eη value of aged RA outstrips that of original sample for the same rubber dosage. For the rubber asphalt samples prepared through adopting the same type and size crumb rubber, the IE values show linear relation with the dosage of crumb rubber, while PE values increase by the exponential growth model continuously with the dosage of crumb rubber. Within a certain temperature range, IE and PE values both show linear relation with the mixing temperature, and show parabola relationship with the processing time. The proposed prediction model can manifest the viscosity composition of rubber asphalt and has an expected fitting precision.

Herein, we propose a simple and effective strategy for designing a ratiometric fluorescent nanosensor. We designed and developed a carbon dots (CDs) based dual-emission nanosensor for vanadium(V) by coating the surface of dye-doped silica nanoparticles with CDs. The fluorescence of dual-emission silica nanoparticles was quenched in acetic acid through potassium bromate (KBrO3) oxidation. V(V) could catalyze KBrO3 oxidation reaction process, resulting in the ratiometric fluorescence quenching of dual-emission silica nanoparticles. We investigated several important parameters affecting the performance of the nanosensor. Under the optimized conditions, the detection limit of this nanosensor reached 1.1ngmL-1 and the linear range from 10 to 800ngmL-1. Furthermore, we found that the sensor was suitable for determination of V(V) in different mineral water samples with satisfactory results.

A simple and effective strategy for designing a ratiometric fluorescent nanosensor was described. A carbon dots (CDs) based dual-emission nanosensor for chromium speciation analysis was developed by coating CDs on the surface of dye-doped silica nanoparticles. The fluorescence of the resulting dual-emission silica nanoparticles was quenched in acetic acid through potassium bromate (KBrO3) oxidation. Cr(VI) was able to catalyze KBrO3 oxidation, resulting in ratiometric fluorescence accelerated quenching response of the dual-emission silica nanoparticles. Several important parameters affecting the nanosensor performance, including acid type, concentrations of KBrO3, and reaction temperature and time were examined. Under the optimized conditions, the detection limit of the nanosensor towards Cr(VI) reached 1.3 ng mL−1, and pretty good linearity was obtained between 20 to 500 ng mL−1. More importantly, the sensor was found suitable for speciation analysis of both Cr(III) and Cr(VI) in different water samples with satisfactory results.

A new supramolecular host-bonded stationary phase for high-performance liquid chromatography (HPLC) was prepared by coupling a 26-membered aromatic-aliphatic-mixed azamacrocycle to 3-chloropropyltrimethoxylsilane-modified silica, which was characterized by infrared spectroscopy and elemental analysis. To understand the role of functional groups and the nano-sized cavity on the azamacrocycle for its chromatographic performance, the chromatographic behavior of the new stationary phase was investigated by using alkylbenzenes, polycyclic aromatic hydrocarbons (PAHs), aromatic amines, and aromatic positional isomers as probes. This stationary phase exhibited a unique chromatographic retention, which was characterized by multiple interactions between the stationary phase and analytes, including hydrophobic, π–π, hydrogen-bonding, and inclusion interactions. At the same time, the embedded azamacrocycle showed remarkable superiority over the C18 phase in terms of shape, planarity, and isomeric recognition in discriminating specific PAHs and isomers and overcoming the negative effect of residual silanol groups. Such a hybrid stationary phase is more versatile and shows great potential in the analysis of complex samples.

A simple and effective strategy for designing a fluorescent probe for bromate was described in this work. Organosilane modified carbon dots were prepared by pyrolysis of citric acid in N-(β-aminoethyl)-γ-aminopropyl methyldimethoxysilane solvent at 230 °C and further doped onto silica nanoparticles by a silylation reaction. The fluorescence of carbon dot doped silica nanoparticles was quenched by bromate in acidic medium. By utilizing this property, the nanoparticle could be used as a sensor to detect bromate. The parameters affecting the performance of the sensor probe such as types of acid medium, acid concentration, reaction temperature, and time were investigated and optimized. The detection limit of the sensor was found to be 1.1 ng mL−1, with a linear range from 8 to 400 ng mL−1 and relative standard deviation of 2.0% (150 ng mL−1, n = 9). The method was successfully applied to the determination of bromate in drinking water samples, and the recoveries were in the range of 96.3%–103.7%.

Numerous attempts have been carried out to develop potential substitutes for petroleum asphalt binders from various biomass resources. This research aims to investigate the effectiveness of partially replacing asphalt binders with thermochemical liquefied products (LPs) of wheat straw. The LPs were obtained by acid-catalyzed liquefaction in organic solvents, based on which nine kinds of bio-asphalt binders distinguished by the type and content of LPs were prepared by mechanical stirring. To evaluate the physicochemical properties of the LPs, the Fourier transform infrared (FTIR) spectroscopy test, gel permeation chromatography (GPC) test, thermogravimetric (TG) test and rotational viscosity (RV) test were conducted. The potential advantages of bio-asphalt binders were explored by the RV test, dynamic shear rheometer (DSR) test, scanning electronic microscopy (SEM) test and FTIR test. The results demonstrate that LPs consist of 79%–88% bio-oils with low molecular weight and a small amount of solid residues. Compared with asphalt binders, more polar groups (e.g. hydroxyl, carbonyl and alcohol, etc.) with low boiling points are found in LPs, resulting in a lower volatilization and degradation temperature. There is a high chance for the fusion of LPs and asphalt binders to be physical integration. Further, the non-Newtonian flow behavior of asphalt binders is deepened by LPs. Nevertheless, better low-temperature cracking resistance and high-temperature performance are found from different types of bio-asphalt binders. It should be noted that the relationship between performances of bio-asphalt binders and the content of LPs needs more attention in further researches.

A rapid and practical method for determining the iodine value (IV) of edible oils or fats with an FTIR spectrometer combined with a quartz cuvette was reported. The sample was diluted with carbon tetrachloride and poured into a quartz cuvette (thickness: 1 cm) to measure the FTIR spectrum in the wavenumber region from 2400 to 4000 cm−1. The peak near 3009 cm−1 corresponding to C–H stretching was corrected with a baseline connecting the absorbance values near 3030 and 2990 cm−1 and used to determine the IV of edible oils and fats by the calibration curve method. A linear relationship between Ap/c, the ratio of the peak absorbance to the concentration of oil, and the IV of oil or fat obtained with the official AOCS titration method was established with a correlation coefficient of 0.9987, and the IVs of 36 samples were determined. The effect of unsaturated fatty acid composition of oil and fat on the FTIR spectra and the predicted IV was discussed. The proposed method was suitable for determining the IV of edible oils and fats in which almost all the olefinic bonds were in the cis configuration.

In order to overcome the disadvantage that the dynamic sliding mode surface of the discrete global sliding mode control has a too long evolution time, a quick discrete global sliding mode control method is proposed. A decay function of the dynamic sliding mode surface which can decay to zero in the finite time is constructed. Thereby, the dynamic sliding mode surface can evolve into the linear sliding mode surface at the given time. Thus, the method not only is strong global robustness, but also can quicken the response of the system and shorten the transition time. The method can be applied in the tension control system of the time delay carbon fiber multilayer diagonal loom. Simulation results prove the validity of the method.

The direct extraction, purification, and enrichment of four aflatoxins (AFs) in wheat were achieved by combining solvent extraction and ionic liquid-based dispersive liquid–liquid microextraction (IL-DLLME). High-performance liquid chromatography coupled with fluorescence detection (HPLC-FD) was applied for the determination of AFs. The feature of the developed technique is that some tedious and time-consuming steps are avoided and the organic solvent consumption is low. The IL-DLLME allows the isolation, purification and enrichment of AFs from the methanol extract using a simple procedure. The effective enrichment was mainly due to the multiple-interaction, including hydrophobic, π-π and hydrogen bonding interactions, between IL and AFs. The parameters affecting the extraction efficiency were thoroughly investigated. This extraction method permits the determination of four AFs with LOD (S/N = 3) and LOQ (S/N = 10) in the range of 0.015–0.20 μg kg−1 and 0.045–0.75 μg kg−1, respectively. The recoveries from four spiked wheat samples ranged from 80.8% to 112.5% with RSDs of 0.8%-4.7% (n = 3), demonstrating the great potential of this proposed procedure for the analysis of AFs in solid samples.

A new adsorbent was synthesized by coupling polymeric ion liquid (PIL) and polymeric styrene (PSt) to polyhedral oligomeric silsesquioxanes (POSS)-modified magnetic nanoparticles. The adsorbent was characterized by transmission electron microscope, vibrating sample magnetometer, x-ray diffraction and fourier transform-infrared spectroscopy. By introduction of branched POSS and dual ligands, the developed POSS/PIL-PSt-based magnetic adsorbent possessed high density of alkyl chains, charged groups and benzene rings and could provide multiple active sites, and showed high extraction efficiency for aflatoxins. By combining with high-performance liquid chromatography-fluorescence detector, the type of ion liquid monomer, dosage ratio of ion liquid to styrene, and some extraction parameters were optimized. Low limit of detection (S/N = 3) and low limit of quantitation (S/N = 10) were achieved with 0.05–0.20 μg/kg and 0.17–0.67 μg/kg, respectively. The recoveries of four aflatoxins for spiked cereal samples were between 87% and 120% with relative standard deviation from 3.2% to 11.2% (n = 3). The satisfactory results indicated that the fabricated adsorbent offered promising application in the extraction of aflatoxins in complicated cereals.