Search

Recently, it is difficult to simulate, analyze and control a real knowledge-based system using the correspondence Petri net (PN) when there exist many current states. To overcome the state explosion problem of PN, an efficient decomposition algorithm is presented to divide a large-scale PN into a series of corresponding sub-PNs by keeping the consistency of dynamic properties. In this novel decomposition approach, an index function is defined to judge the subnet needs to be decomposed or not. Furthermore, an exhaustive analysis on the consistency of related dynamic properties is also discussed between the original PN and the corresponding sub-PNs. Finally, a case study is carried out to illustrate the feasibility and validity of the proposed approach.

In order to reduce the storage capacity of fonts and improve the display quality of characters, this study proposes an approach to generate square Hmong characters using intelligent derivation mechanism. In the proposed approach, the process of generating square Hmong characters is transformed into the process of solving the bounding box of components using binary tree. Thus, various square Hmong characters can be generated by repeatedly performing topological transformation of limited components. A corresponding intelligent derivation model is developed to get square Hmong characters based on the glyph data of objective components obtained by intelligent derivation. Meanwhile, deterministic finite automata is also used to represent the square of square Hmong characters. Testing results of the editing software developed based on this model demonstrate that the square Hmong characters generated by the proposed intelligent derivation mechanism can meet the needs of practical applications.

The application of the magnetic nanocatalysts is a rapidly growing field for the development of sustainable and green processes. Magnetic separation not only avoids the need for catalyst filtration or centrifugation after completion of the reaction, but also provides practical techniques for recovering these catalysts. Multicomponent reactions are recognized as very powerful tools in synthetic organic and medicinal chemistry for the synthesis of the complex products in a single step from simple starting materials. The combination of magnetic nanocatalysts and multicomponent reactions will become an emerging strategic research area and is an ideal blend for the development of sustainable methods in green synthetic chemistry. This review focuses on the synthesis and application of magnetic nanocatalysts as novel task-specific catalysts for multicomponent reactions in recent years.

A novel magnetic metal–organic framework, NiFe2O4@MOF-5, has been prepared and characterized using spectroscopic, microscopic, and magnetic techniques (FT-IR, XRD, TEM, SEM, EDX, and VSM). This magnetically separable catalyst exhibited high catalytic activity for the synthesis of a variety of 2-substituted alkyl and aryl(indolyl)kojic acid derivatives via a one-pot, three-component reaction of aldehyde, indole, and kojic acid under solvent-free conditions. The catalyst can be easily magnetically separated and exhibits significant recyclability, with no significant loss of activity after six consecutive runs.

An efficient and eco-friendly procedure has been developed for synthesis of naphthoquinone-fused oxazine derivatives via one-pot pseudo four-component reaction of 2-hydroxy-1,4-naphthoquinone, aromatic amine and formaldehyde in water under ultrasound irradiation. This protocol has the advantages of being catalyst-free, with short reaction times and high yields, and being environmentally benign with an easy work-up.

Harmony search (HS) algorithm has received widely attention in various fields because of simple operation and outstanding performance. However, there exists some bottlenecks which hinders the further development of HS algorithm, such as easy trapping into local optimum and slow convergence velocity.This paper proposes an improvement HS algorithm by using segmented search strategy (SHS) to overcome these drawbacks. Comparative experiments reveal the proposed SHS algorithm has perfect performance, especially in high dimensions.

Part-of-speech (POS) tagging is a basic problem that needs to be solved in the informationization of Chinese-Hmong mixed text including square Hmong characters, so far no one has studied it. This paper proposes a POS tagging approach for Chinese-Hmong mixed text by utilizing improved Hidden Markov Model (HMM) to expand contextual information. The results of comparative experiments based on cross-validation reveal the proposed approach has perfect performance, and is able to obtain tagging results with good consistency and high coverage.

Artificial bee colony algorithm (ABC) and particle swarm optimization (PSO) are both famous optimization algorithms that have been successfully applied to various optimization problems, especially in function optimization. Those two algorithms have been attracting more and more research interest because of their efficiency and simplicity. However, PSO has poor exploration capabilities and thus is easy to fall into the local optimum; Likewise, ABC has low convergence speed. To address these shortcomings, firstly, we improved the ABC with the combination of greedy selection and crossover, secondly, a sine-cosine method will be used to help PSO jump into local optimal. Finally, a new hybrid algorithm based on improved ABC and PSO are proposed. Moreover, four functions are used to verify the effectiveness of the proposed algorithm, and the results show that, compared with other well-known algorithms, ABC-PSO is more efficient, faster and more robust in function optimization.

An efficient and simple synthetic approach has been developed for the preparation of biologically interesting spiro[oxindole-3,4’-(4′H-pyran)] derivatives via visible light-mediated one-pot, three-component reaction of isatins, 1,3-dicarbonyl compounds and malononitrile by using an inexpensive organic dye, Na2 eosin Y, as the photocatalyst in aqueous ethyl lactate at ambient temperature. The substrate scope of this three-component reaction is expanded to linear 1,3-dicarbonyl compounds as viable starting materials. All rights reserved.

Fuzzy Petri net (FPN) is a powerful tool to execute the fault diagnosis function for various industrial applications. One of the most popular approaches for fault diagnosis is to calculate the corresponding algebra forms which record flow information and three parameters of value of all places and transitions of the FPN model. However, with the rapid growth of the complexity of the real system, the scale of the corresponding FPN is also increased sharply. It indicates that the complexity of the fault diagnosis algorithm is also raised due to the increased scale of vectors and matrix. Focusing on this situation, a bidirectional adaptive fault diagnosis algorithm is presented in this article to reduce the complexity of the fault diagnosis process via removing irrelevant places and transitions of the large-scale FPN, followed by the correctness and algorithm complexity of the proposed approach that are also discussed in detail. A practical example is utilized to show the feasibility and efficacy of the proposed method. The results of the experiments illustrated that the proposed algorithm owns the ability to simplify the inference process and to reduce the algorithm complexity due to the removal of unnecessary places and transitions in the reasoning path of the appointed output place.

Fuzzy Petri net (FPN) has been extensively applied in industrial fields for knowledge-based systems or systems with uncertainty. Although the applications of FPN are known to be successful, the theoretical research of FPN is still at an initial stage. To pave a way for further study, this work explores related dynamic properties of FPN including reachability, boundedness, safeness, liveness and fairness. The whole methodology is divided into two phases. In the first phase, a comparison between elementary net system (EN_system) and FPN is established to prove that the FPN is an extensive formalism of Petri nets using a backwards-compatible extension method. Next, current research results of dynamic properties are utilized to analyze FPN model. The results illustrate that FPN model is bounded, safe, weak live and fair, and can support theoretical evidences for designing related decomposition algorithm.

An highly efficient and environmentally friendly process for the synthesis of α-aminophosphonates has been devised, through a one-pot three-component condensation of various aldehydes, amines and triethyl phosphate in water-ethyl lactate under ultrasonic irradiation conditions at room temperature. The expected products were obtained in high yield without the need for any additional catalyst.

Deep eutectic solvents (DESs), also known as deep eutectic ionic liquids (DEILs) or low-melting mixtures (LMMs) or low transition temperature mixtures (LTTMs) in the literature, have become more and more attractive in recent years due to their interesting properties and benefits, such as low cost of components, easy to prepare, tunable physicochemical properties, negligible vapor pressure, non-toxicity, biorenewability and biodegradability. These eutectic mixtures have been widely used as green and sustainable media as well as catalysts in many chemical processes. This review focuses on recent advances using DESs in organic reactions including addition reactions, cyclization reactions, replacement reactions, multicomponent reactions, condensation reactions, oxidation reactions, and reducing reactions.

Superparamagnetic CuFeO2 nanoparticles were prepared and characterized by XRD, SEM, TEM, FRIR spectroscopy, and vibrating sample magnetometry techniques. The catalytic activity of CuFeO2 nanoparticles was investigated in the one-pot, three-component reaction of 2-aminopyridines, aldehydes, and alkynes using citric acid–dimethylurea melt as a green solvent. An array of imidazo[1,2-a]pyridines were obtained in good to excellent yields. The catalytic system can be successfully reused six times with keeping its catalytic performance.

The actual preventive and therapeutic effects of alkalinizing urine on melamine-induced bladder stones (cystolith) are not completely known. Using an ideal model, two experiments were conducted in Balb/c mice. The mice were fed a normal diet in controls and a melamine diet in the other groups. The first day was set as experiment-day 1. In "Experiment 1", either low-/mid-/high-dose sodium bicarbonate (SB) or sterile water was administered by intragastric perfusion (once daily) to the mice for 14 days. Relative to the model group, the mean pH of the urine in the SB groups was significantly elevated at 3 h after SB administration, with a significant decrease in cystolith incidence on experiment-day 14. In "Experiment 2", on experiment-day 12, the melamine diet was replaced by a normal diet in 4 groups with melamine withdrawal (MW). Meanwhile, either mid-/high-dose SB or sterile water was administered by intragastric perfusion (once) to the mice in the corresponding groups. On experiment-day 12, after an additional 8 h, the cystolith incidence was significantly reduced in the high-SB, MW + mid-SB and MW + high-SB groups than in the model group. In conclusion, low urinary pH is one of the main determinants of the formation of melamine-associated stones, urinary alkalinization can be achieved by a proper dose of oral SB, and SB acts to prevent and treat melamine-induced cystoliths in mice.

A convenient three-step procedure has been developed for synthesis of substituted 2-aminobenzophenones from substituted anilines. The anilines are first protected as acetanilides, by reaction with acetic anhydride. These are then benzoylated with (trichloromethyl)benzene in the presence of aluminium-generated 2-acetamidobenzophenone. Finally, removal of the acetyl group from the amino group provides the substituted 2-aminobenzophenones in moderate to good yields.

A novel magnetic nano-CoFe2O4 supported Sb ([CoFe2O4@SiO2–DABCO–Sb]) was successfully constructed, which exhibited high catalytic activity for one-pot three-component synthesis of multisubstituted pyrroles in the reaction of amines, nitroolefin and 1,3-dicarbonyl compounds. The magnetic heterogeneous catalyst could be easily recovered using an external magnet and reused many times without significant loss of catalytic activity.

A facile and highly efficient protocol for the one-pot, four-component reaction of ethyl acetoacetate, hydrazine hydrate, aromatic aldehydes and barbituric acid has been developed using meglumine as an inexpensive, biodegradable and reusable catalyst. This methodology provides a mild and fast route to structurally diverse tricyclic fused pyrazolopyranopyrimidines in good to excellent yields. Simplicity, room temperature reaction conditions, a green solvent, an easy work-up process, inexpensive price and reusability of the catalyst are the main advantages of this method.

Meglumine, a bio-based chemical, was demonstrated to be a highly efficient and reusable catalyst for the synthesis of a series of pyranopyrazole derivatives via a one-pot, four-component reaction of carbonyl compound or isatin, hydrazine hydrate, malononitrile, and β-keto ester in EtOH–H2O. The catalyst was found to work extremely for aldehydes, ketones or isatins at room temperature to give the corresponding dihydropyrano[2,3-c]pyrazole or spiro[indoline-3,4′-pyrano[2,3-c]pyrazole] derivatives in high yields. The salient features of this new methodology are broad substrate scope, room temperature reaction conditions, short reaction times, high yields, easy work-up process, reusability of catalyst, and the absence of hazardous organic solvents.

Interestingly, the substitution of epoxides (I) and (III) exerts a significant effect on the ring-opening direction.

Four-component coupling of amines, aldehydes, 1,3-dicarbonyl compounds, and nitromethane has been achieved in gluconic acid aqueous solution (GAAS) to produce polysubstituted pyrroles in high yield. Gluconic acid aqueous solution could be recycled and reused several times without significant loss of its efficiency.

A new magnetic nanoparticle-supported antimony catalyst was prepared and evaluated as a recoverable catalyst for Clauson-Kaas reaction. The reaction proceeds efficiently in aqueous medium to give the corresponding N -substituted pyrroles in high yield. The immobilized catalyst could be easily recovered by magnetic separation and recycled for six times without significant loss of its catalytic activity.

A general, efficient, and green method for one-pot synthesis of functionalized spirooxindoles through three-component condensation reaction of isatins, cyclohexane-1,3-diones, and barbituric acids is described employing gluconic acid aqueous solution (GAAS) as a novel reaction medium and catalyst. The reaction medium could be recycled and reused several times without significant loss of its efficiency.

Dodecyl benzenesulfonic acid functionalized silica-coated magnetic nanoparticles (γ-Fe2O3@SiO2-DDBSA) were readily prepared and identified as an efficient catalyst for the synthesis of a library of spirooxindole-pyrimidine derivatives by three-component condensation reaction of barbituric acids, isatins and cyclohexane-1,3-diones. The aqueous reaction medium, easy recovery of the catalyst using an external magnet, and high yields make the protocol sustainable and economic.

A highly atom-economic one-pot synthesis of functionalized tetrahydropyridines by a multicomponent condensation reaction of β-keto ester, two equivalents of aromatic aldehyde, and two equivalents of amine in the presence of a catalytic amount of cerium ammonium nitrate (CAN) is reported. In this way, a series of pharmacologically interesting substituted piperidine derivatives were obtained in moderate to good yields at room temperature.

A practical and efficient procedure for the one-pot multicomponent couping of aryl aldehydes, 2-naphthol and cyclic 1,3-dicarbonyl compounds using perchloric acid adsorbed on silica gel (HClO 4 -SiO 2 ) as a highly efficient, inexpensive, convenient, reusable heterogeneous catalyst under solvent-free conditions has been developed. Various biologically important 12-aryl-8,9,10,12-tetrahydrobenzo[α]xanthen-11-one derivatives have been efficiently synthesized in high to excellent yields. The present approach offers several advantages such as shorter reaction times, simple work-up, excellent yields, low cost, and mild reaction conditions. Furthermore, the catalyst can be recovered simply and reused without appreciable loss of its catalytic activity.

Nanostructured SnO 2 was prepared by the sol–gel method. Aniline monomer was polymerized in the suspension of nanocrystalline SnO 2 to form inorganic–organic composite materials, in which SnO 2 nanoparticles were embedded within netlike polyaniline (PANI). Structural and morphological characterizations of SnO 2 and PANI/SnO 2 were carried out using power X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Their electrochemical properties were also investigated using cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. The as-prepared composites had excellent properties in the capacitance, and its specific capacitance was up to 305.3 F g −1 with a specific energy density of 42.4 Wh kg −1 and a coulombic efficiency of 96%. The results indicated that the PANI/SnO 2 had a synergistic effect of the complementary properties of both components.

Cobalt hydroxide was synthesized via a new approach, in which the gel was prepared by the reaction of Co(NO 3 ) 2 solution with citric acid, and then the precursors were obtained after thermal treatment, finally the precursors reacted with KOH solution to produce the samples. The components of the precursors were measured by Fourier transforms infrared (FT-IR) spectroscopy. The morphology and structure of samples were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results indicate that the as-prepared materials are β-Co(OH) 2 with sheet-like morphology. The effect of the treatment temperature for the precursor on sheet size was discussed in detail. Cyclic voltammetry and constant current charge/discharge measurements show that the prepared cobalt hydroxide exhibits excellent capacitance performance. The specific capacitance is up to 416.7 F g −1 at a constant current charge/discharge test of 5 mA.

An efficient method for the enamination of 1,3-dicarbonyl compounds by employing ceric ammonium nitrate (CAN) as the catalyst has been described. A variety of β-amino-α,β-unsaturated ketones and esters have been synthesized in excellent yield within a short reaction time under solvent-free conditions.

The polyaniline/polysulfone (PAN/PSF) composite films were prepared by electropolymerization, and then platinum was deposited into this composite film to obtain the platinum-modified polyaniline/polysulfone(Pt/PAN/PSF) composite film electrodes. Their component, morphology and structure were characterized by FTIR spectra, scanning electron microscopy and energy dispersive X-ray spectroscopy. The results show that the composite film has a bi-layer structure with asymmetrical pores, and the platinum particles are homogeneously dispersed in the modified film electrodes. The cyclic voltammetry and electrochemical impedance spectroscopy techniques were applied to investigate the electrochemical properties and the electrocatalytic activity of the modified film electrodes, which show a promotive action for methanol oxidation and the methanol oxidation under a diffusion-controlled process. Keywords: PAN/PSF composite film, Pt/PAN/PSF electrode, Preparation, Methanol oxidation, Electrocatalytic activity

A novel magnetic NiFe2O4 supported glutamate–copper catalyst was prepared in a convenient and ecofriendly manner and characterized using FTIR, XRD, EDX, TEM, SEM, XPS and VSM. This magnetic catalyst exhibited excellent catalytic activity for the synthesis of a wide variety of 1,4-disubstituted-1,2,3-triazoles via one-pot three-component click reactions of sodium azide, non-activated terminal alkynes, and different azide precursors such as epoxides, benzyl chlorides, and aryl boronic acids at room temperature in water. This procedure has some advantages such as an aqueous reaction medium, ambient reaction conditions, high yields, wide substrate scope, easy separation of the catalyst using an external magnet and efficient recycling.