Coal based carbon dots: recent advances in synthesis, properties, and applications

Carbon dots are zero-dimensional carbon nanomaterials with quantum confinement effects and edge effects, which have aroused great interests in many disciplines such as energy, chemistry, materials, and environmental applications. They can be prepared by chemical oxidation, electrochemical synthesis, hydrothermal preparation, arc discharge, microwave synthesis, template method, and many other methods. However, the raw materials' high cost, the complexity and environmental-unfriendly fabrication process limit their large-scale production and commercialization. Herein, we review the latest developments of coal-based carbon dots about selecting coal-derived energy resources (bituminous coal, anthracite, lignite, coal tar, coke, etc.) the developments of synthesis processes, surface modification, and doping of carbon dots. The coal-based carbon dots exhibit the advantages of unique fluorescence, efficient catalysis, excellent water solubility, low toxicity, inexpensive, good biocompatibility, and other advantages, which hold the potentiality for a wide range of applications such as environmental pollutants sensing, catalyst preparation, chemical analysis, energy storage, and medical imaging technology. This review aims to provide a guidance of finding abundant and cost-effective precursors, green, simple and sustainable production processes to prepare coal-based carbon dots, and make further efforts to exploit the application of carbon dots in broader fields

Flashover in Aircraft Cargo Compartment at Different Pressures: Experimental and Modeling Study

The increasing incidence of aircraft cargo compartment fires in recent years has caused heavy losses and drawn attention to understanding the combustion process, especially under low pressure. The present paper aims at exploring the conditions of flashover at different pressures. Experiments were conducted in Guanghan (96 kPa) and Kangding (60 kPa), which are located at different altitudes. Five different sizes of pool fires were tested and smoke temperature and heat flux were measured for flashover criteria analysis. Corresponding simulations were performed using a commercial software FDS to examine the pressure effect on the flashover phenomenon and to validate the simulation results. The critical conditions for the onset of flashover in a 1/4 MPS compartment were found to be (1) an average upper layer temperature of about 450 °C at 96 kPa or about 550 °C at 60 kPa, and (2) radiant heat flux at floor level of about 10 to 15 kW/m2 at 96 kPa or 20 to 25 kW/m2 at 60 kPa. By using the average upper layer temperature as a criterion in modeling, a relatively accurate prediction of flashover onset time could be obtained at 96 kPa and a delay of about 25 s was found at 60 kPa

Investigation on Safety Dynamic Evolution Mechanism of a Distributed Low Carbon Manufacturing System with Large Time Delay

In order to reveal the inducing factors and safety dynamic evolution mechanism of frequent personal injury accidents under a low carbon manufacturing process, a nonlinear safety dynamic evolution model of a distributed low carbon manufacturing system with large time delay is established. The established model is then verified by simulation results from mathematical analysis and dynamic evolution. Moreover, qualitative analysis on nonlinear safety dynamic evolution and the trend of human–machine safety under a low carbon manufacturing process is investigated. Finally, an application case of the established model is studied. The key results are as follows: (1) There are four dynamic regions, namely the safety area I, the deterioration area II, the asymptotically stable safety area III, and the enhancement area IV of the safety ability in the interaction evolution model of carelessness and safety levels; (2) There are two singularities in the dynamic evolution model of the man–machine safety system with large time delay under a low carbon manufacturing process; (3) The equilibrium points of the human–machine safety system are El = (0, 0) and E2 = (0.5333, 0.2489), while changes in the carelessness level have a serious block effect on safety development with time; (4) For the radial tire casing process, the low carbon development trend of the technological process of radial tire casing is good, but low carbon structure and management have slightly lower low carbon levels. This work provides a theoretical basis for the safety evaluation and control of the distributed low carbon manufacturing human–machine safety system with large time delay

A Novel Divide-and-Conquer Model for CPI Prediction Using ARIMA, Gray Model and BPNN

AbstractThis paper proposes a novel divide-and-conquer model for CPI predictionwith the existing compilation method of the Consumer Price Index (CPI) in China. Historical national CPI time series is preliminary divided into eight sub-indexes includingfood, articles for smoking and drinking, clothing, household facilities, articles and maintenance services, health care and personal articles, transportation and communication, recreation, education and culture articles and services, and residence. Three models including back propagation neural network (BPNN) model, grey forecasting model (GM (1, 1)) and autoregressive integrated moving average (ARIMA) model are established to predict each sub-index, respectively.Then the best predicting result among the three models’ for each sub-index is identified. To further improve the performance, special modification in predicting method is done to sub-CPIs whose forecasting results are not satisfying enough. After improvement and error adjustment, we get the advanced predicting results of the sub-CPIs.Eventually, the best predicting results of each sub-index are integrated to form the forecasting results of the national CPI. Empirical analysis demonstrates that the accuracy and stability of the introduced method in this paper is better than many commonly adopted forecasting methods, which indicates the proposed method is an effective and alternative one for national CPI prediction in China

Study on the Parameters of Ice Clouds Based on 1.5 µm Micropulse Polarization Lidar

Dust aerosols can participate in the heterogeneous nucleation process as effective ice nucleation particles, thus changing the physical properties of clouds. In this paper, we used an eye-safe 1550 nm micropulse polarization single photon lidar combined with meteorological stations, HYSPLIT backward trajectory analysis, ERA5 reanalysis data, CALIPSO, Himawari-8 and Terra-MODIS satellite data to compare the difference in cloud characteristics between dust and clean cirrus cases in Jinan from 26–29 March 2022. The study found that the aerosol affected the cloud effective radius, and the cloud top temperature impacted the properties of depolarization of dust ice clouds. According to the statistical results of the upper and lower quartiles, the depolarization ratio (DPR) range of dust cirrus on 26 March was 0.46–0.49, a similar range to the clean cirrus, while that of dust cirrus on 27 March was 0.54–0.59, which seemed much larger. Different height and temperature conditions lead to differences in the habits of ice crystals in clouds, thus changing the DPR. However, the range of the DPR between clean cirrus and dust cirrus showed no obvious difference, as the former was 0.43–0.53 and the latter was 0.46–0.59. Under the condition of higher aerosol loading, the lidar range-corrected signal (RCS) of cirrus clouds was stronger, and the cloud effective radius was 48 μm, larger than that of clean cirrus (32 μm). This may be the effect of dust on the microphysical properties of clouds. This study discusses the indirect effects of dust aerosols on cirrus clouds and the underlying mechanisms from the perspectives of microphysics and optics, which can provide more references for urban air pollution processes and aerosol-cloud interactions

Study on the Parameters of Ice Clouds Based on 1.5 µm Micropulse Polarization Lidar

Dust aerosols can participate in the heterogeneous nucleation process as effective ice nucleation particles, thus changing the physical properties of clouds. In this paper, we used an eye-safe 1550 nm micropulse polarization single photon lidar combined with meteorological stations, HYSPLIT backward trajectory analysis, ERA5 reanalysis data, CALIPSO, Himawari-8 and Terra-MODIS satellite data to compare the difference in cloud characteristics between dust and clean cirrus cases in Jinan from 26–29 March 2022. The study found that the aerosol affected the cloud effective radius, and the cloud top temperature impacted the properties of depolarization of dust ice clouds. According to the statistical results of the upper and lower quartiles, the depolarization ratio (DPR) range of dust cirrus on 26 March was 0.46–0.49, a similar range to the clean cirrus, while that of dust cirrus on 27 March was 0.54–0.59, which seemed much larger. Different height and temperature conditions lead to differences in the habits of ice crystals in clouds, thus changing the DPR. However, the range of the DPR between clean cirrus and dust cirrus showed no obvious difference, as the former was 0.43–0.53 and the latter was 0.46–0.59. Under the condition of higher aerosol loading, the lidar range-corrected signal (RCS) of cirrus clouds was stronger, and the cloud effective radius was 48 μm, larger than that of clean cirrus (32 μm). This may be the effect of dust on the microphysical properties of clouds. This study discusses the indirect effects of dust aerosols on cirrus clouds and the underlying mechanisms from the perspectives of microphysics and optics, which can provide more references for urban air pollution processes and aerosol-cloud interactions

Design, Synthesis, and Biological Activities of Novel 2-Cyanoacrylate Compounds Containing Substituted Pyrazolyl or 1,2,3-Triazolyl Moiety

To develop novel 2-cyanoacrylate derivatives with potential bioactivity, a number of 2-cyanoacrylate compounds, including substituted pyrazole or 1,2,3-triazole ring, were designed, prepared, and structurally detected by 1H NMR, 13C NMR, and elemental analysis. The biological assessment displayed that some designed compounds had significant herbicidal activities against Brassica juncea, Chenopodium serotinum, Rumex acetosa, Alopecurus aequalis, Polypogon fugax, and Poa annua at a dosage of 1500 g/ha. Furthermore, some derivatives still expressed satisfactory herbicidal activities against Brassica juncea, Chenopodium serotinum, and Rumex acetosa when the dosage was lowered to 150 g/ha, especially the inhibitory effects of compounds 9a, 9d, 9f, 9i, 10a, 10b, 10e, and 10n against Brassica juncea were all over 80%, compounds 9d, 9f, 9g, 9h, 9i, 10h, 10i, 10m, 10n, and 10o possessed more than 70% inhibition rates against Chenopodium serotinum, and compound 9d indicated 70% herbicidal activity against Rumex acetosa. These results provided an important basis for further design and discovery of biologically active 2-cyanoacrylate compounds

Fabrication and properties of pink 3 mol% yttria‐stabilized zirconia ceramics with high toughness

To broaden the applications of yttria-stabilized zirconia (YSZ) in mobile phone back panels and high-end decorative materials, the 3 mol% YSZ (3YSZ) ceramics doped with erbium oxide (Er2O3) as colorant were successfully sintered at 1250 and 1350°C in air. The influences of Er2O3-doping concentration and sintering temperature on the phase, microstructure, color, and mechanical properties of the pink Er2O3-3YSZ ceramics were investigated. As the Er2O3 concentration increased, the redness value a* gradually increased, while the yellowness value b* and the lightness value L* gradually decreased. The highest value a* and b* of Er2O3-3YSZ ceramics reached absolute values of 15.2 and 4.5, respectively. The effect of Er2O3 concentration is also depicted in detail, which also affects the mechanical properties including hardness and fracture toughness of the ceramics. The maximum hardness and fracture toughness of Er2O3-3YSZ ceramics reached 13.9 ± 0.3 GPa and 6.21 ± 0.20 MPa·m1/2, respectively. The hardness of the ceramics exceeds 12.5 GPa, which is the required market index for further practical application. This work provides a method for preparing 3YSZ ceramics with excellent mechanical properties and bright pink color, which has the potential to be used in the fields of advanced and superior electronics in particular

Risk factors of postoperative delirium following spine surgery: A meta-analysis of 50 cohort studies with 1.1 million participants

Objectives: Postoperative delirium (POD) is considered to be a common complication of spine surgery. Although many studies have reported the risk factors associated with POD, the results remain unclear. Therefore, we performed a meta-analysis to identify risk factors for POD among patients following spinal surgery. Methods: We systematically searched the PubMed, Embase and the Cochrane Library for relevant articles published from 2006 to February 1, 2023 that reported risk factors associated with the incidence of POD among patients undergoing spinal surgery. The Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines were followed, and random effects models were used to estimate pooled odds ratio (OR) estimates with 95 % confidence intervals (CIs) for each factor. The evidence from observational studies was classified according to Egger's P value, total sample size, and heterogeneity between studies. Results: Of 11,329 citations screened, 50 cohort studies involving 1,182,719 participants met the inclusion criteria. High-quality evidence indicated that POD was associated with hypertension, diabetes mellitus, cardiovascular disease, pulmonary disease, older age (>65 years), patients experiencing substance use disorder (take drug ≥1 month), cerebrovascular disease, kidney disease, neurological disorder, parkinsonism, cervical surgery, surgical site infection, postoperative fever, postoperative urinary tract infection, and admission to the intensive care unit (ICU). Moderate-quality evidence indicated that POD was associated with depression, American Society of Anesthesiologists (ASA) fitness grade (>II), blood transfusion, abnormal potassium, electrolyte disorder, length of stay, inability to ambulate and intravenous fluid volume. Conclusions: Conspicuous risk factors for POD were mainly patient- and surgery-related. These findings help clinicians identify high-risk patients with POD following spinal surgery and recognize the importance of early intervention