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An asymmetric cascade reaction catalyzed by a chiral N,N′-dioxide–Dy(iii) complex was realized to construct the valuable [6,5,5,6] tetracyclic spiroindolines with good yields and enantioselectivities by a concise and one-step protocol.

Composite insulators are widely used in the power transmission system. Operating in the outdoor environment, the composite insulator will be inevitably polluted by natural contamination with the increase of service life, and contamination on the surface is one of the main reasons for the abnormal temperature rise of the insulator. In this study, the rated voltage was applied to the kieselguhr sample under a high‐humidity environment, and its temperature rise characteristics and leakage current were tested. The research results show that the temperature rise in contamination falling‐off region is significant and the leakage current is greater than the clean sample. By analysing the phenomenon with the help of the circuit model, it is concluded that the high resistance and voltage in contamination falling‐off region leads to high heating power of the polarisation loss.

An asymmetric three-component 1,3-dipolar cycloaddition of 3,4-dihydroisoquinolines, bromoacetates and α,β-unsaturated pyrazole amide is realized by using a chiral N,N'-dioxide-Y(OTf)3 complex as the catalyst. The process includes a base-promoted formation of dihydroisoquinolium ylides in situ, and a chiral Lewis acid-catalyzed asymmetric [3+2] cycloaddition with α,β-unsaturated pyrazole amides. A series of hexahydropyrrolo-isoquinolines are obtained in moderate to good yields with excellent diastereo- and enantioselectivities.

Pollution flashover occurs more easily on contaminated transmission line insulators, which causes huge losses to the power system. In order to prevent the pollution flashover, the first step is to identify the contamination grade of insulator. This paper identifies the pollution grade through the color characteristic of visible light image. Firstly, the image segmentation method based on the randomized Hough transform method is adopted to achieve the surfaces of the red composite insulators with different contamination grades in the transformer substations of Heilongjiang Power Grid. Then, a total of 36 kinds of characteristic of $R,\ G,\ B,\ H,\ S$ and $V$ component images are calculated. According to Fisher criterion, the mean and median of S component, which can significantly represent the contamination grade, are selected. Finally, a support vector machine for classification decision is designed. Experimental results show that the identification accuracy of the composite insulators reaches 97.5%, which proves this method can be used for identification of composite insulator contamination grade.

Ideal adsorbents are featured by both high adsorption capacity and high adsorption rate. Current adsorptive membranes enjoy good mass transfer performance but have limited sorption capacity. Microporous organic polymer has superiorities of small pore size and high surface area which is conductive to high adsorption capacity, but usually suffers from high mass transfer resistance. In this work, the polymer of intrinsic microporosity PIM-1 was fabricated into microfiber membranes by electrospinning for carbendazim and phenol adsorption. The PIM-1 and its electrospun membranes were characterized by 1H NMR, GPC, ATR-FTIR, FESEM, TG and BET measurements. The electrospun PIM-1 membrane was demonstrated to have hierarchical porous structure with high surface area. The equilibrium adsorption capacity for carbendazim and phenol was 0.084 mmol/g and 0.804 mmol/g, respectively. The adsorption isotherm fits well with Langmuir model and the adsorption kinetic can be described by film diffusion and chemical reaction model. The membrane can retain 95% of its initial capacity after cycling 10 times. Both the sorption capacity and kinetic coefficients are high when comparing with other sorbents for either carbendazim or phenol, demonstrating that the electrospun PIM-1 is a good adsorbent.

An enantioselective synthesis of α-aminoketone derivatives were readily available through a tandem insertion-[1,3] O-to-C rearrangement reaction. The rhodium salt and chiral N,N'-dioxide-indium(III) complex make up relay catalysis, which enables the O-H insertion of benzylic alcohols to N-sulfonyl-1,2,3-triazoles, and asymmetric [1,3]-rearrangement of amino enol ether intermediates, subsequently. Preliminary mechanistic studies suggested that the [1,3] O-to-C rearrangement step proceeded through an ion pair pathway.

Isatin-derived ketimines undergo enantioselective alkynylation reactions in the presence of copper iodide and easily accessible guanidine-amides. The corresponding 3-alkynyl-3-aminooxyindoles are obtained in up to 95% yield and 96% ee. The guanidine plays a role in the formation of copper acetylide and the enantiodetermining step and the basic additive is excluded.

VaR is now widely used as an important tool to evaluate and manage financial risks. In particular, it is important to select an appropriate volatility model for the rate of return of financial assets. In this study, both univariate and multivariate models are considered to evaluate VaR of the portfolio composed of KOSPI, Hang-Seng, Nikkei indexes, and their performances are compared through back testing techniques. Overall, multivariate models are shown to be more appropriate than univariate models to estimate the portfolio VaR, in particular DCC and ADCC models are shown to be more superior than others.

A Ni–Co bimetallic catalyst, Ni–Co/La2O3/Al2O3, was prepared by conventional incipient wetness impregnation. It shows a high level of activity and excellent stability for biogas reforming. This work examines how operating conditions, such as the reaction temperature, operating pressure, feed ratio, gas hourly space velocity (GHSV), and CO2 excessive coefficient, affect the catalytic performances of the catalyst. The experimental biogas is simulated with CH4 and CO2 at a molar ratio of 1, without any dilute gas. The catalyst was also characterized by XRD, BET, TEM and TG-DSC. In a stability test of 510 h under the conditions of 800 °C, 1 atm, and a GHSV of 6000 ml gcat−1 h−1, the average coking rate over the catalyst was only about 0.0374 mg gcat−1 h−1. The experimental results also indicate that the dynamic equilibrium between the deposition and gasification of carbon deposited on the surface of the catalyst can be established during the reaction. The aggregation of metallic Ni/Co and the formation of filamentous carbon over the surface of the catalyst can be inhibited effectively. During the last 50 h of the 510 h stability test, the average conversion of CH4 and CO2, the selectivity to H2 and CO, and ratio of H2/CO were 95.2%, 96.7%, 95.0%, 98.3%, and 0.96, respectively.

Ni/Co bimetallic catalysts supported by commercial γ-Al2O3 modified with La2O3 for biogas reforming were prepared by conventional incipient wetness impregnation. The catalysts were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), BET surface area and porosity analysis (BET), H2 temperature-programmed reduction (H2-TPR), transmission electron microscopy (TEM) and thermogravimetry coupled to differential scanning calorimetry (TG–DSC). XRD and XPS analysis revealed that a Ni/Co alloy was formed in the bimetallic catalysts. The Ni/Co ratio could be adjusted to improve pore textural properties, which enhanced the metal particle dispersion and resulted in smaller metal particle size, and thus increased the catalytic activity and resistance to carbon deposition. The activity and stability of the catalysts for biogas reforming was tested at 800 °C, ambient pressure, GHSV of 6000 ml gcat−1 h−1 and a CH4/CO2 molar ratio of 1 without dilute gas. Experimental results showed that the catalytic activity could be closely related to the Ni/Co ratio. The bimetallic catalyst 7Ni3Co/LaAl exhibited better catalytic and anti-coking performance due to smaller metal particles, higher metal dispersion, uniform pore distribution, surface enrichment of Co, as well as the synergetic effect between Ni and Co. During a 290 h stability test over the catalyst 7Ni3Co/LaAl, the average conversion of CH4 and CO2, selectivity to H2 and CO, and ratio of H2/CO were 93.7%, 94.0%, 94.9%, 97.8%, and 0.97, respectively. The average coking rate was 0.0946 mg gcat−1 h−1.

Mobile sink is a kind of node with mobility in wireless sensor networks, which is proved to balance the energy consumption of the whole network effectively and solve the "Energy hole" problem. The central focus of the study is to build a dynamic route from the sensor to the mobile sink. A mobile awareness routing protocol for mobile wireless sensor networks based on optimal relay nodes (MAOR) is proposed. First, the network is divided into clusters according to LEACH. Then the nodes percept the movement of the mobile sink and found the relay nodes on the optimal forward position calculated by the relevance of communication distance and energy consumption. Finally, the data collected by the clusters is transmit for the sensor to the mobile sink through the optimal relay nodes. Experiment result show that the MAOR is of benefit to achieve an evident improvement of network lifetime.