模拟深海采矿环境下混响的局部平稳性分析

针对深海采矿环境中强混响干扰下目标回波提取困难的问题,提出了海底强混响环境的模拟方法,在此基础上建立了采矿模拟环境中混响干扰的AR模型,并利用建立的AR模型计算了模拟环境中信号的Itakura距离.以建立的AR模型及Itakura距离为基础,建立了海底强混响仿真模型,对不同Itakura距离下的仿真信号及己知Itakura距离的大量实验数据分段预白化处理.仿真和实验数据处理结果表明模拟采矿环境下混响具有局部平稳性.     

Enhancing the electrochemical performance of Li1.2Ni0.2Mn0.6O2 by surface modification with nickel–manganese composite oxide

Li-rich layered Li_1.2Ni_0.2Mn_0.6O₂ has been surface modified by nickel–manganese composite oxide (Ni_0.5Mn_1.5O _x ) to serve as a novel cathode material with novel layered spinel structure for lithium-ion battery. The as-prepared Li_1.2Ni_0.2Mn_0.6O₂ before and after surface modification by Ni_0.5Mn_1.5O _x as well as simply blended Li_1.2Ni_0.2Mn_0.6O₂ with spinel LiNi_0.5Mn_1.5O₄, have been characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electronic microscopy, and differential scanning calorimetry. Electrochemical studies indicate that the Ni_0.5Mn_1.5O _x surface modified Li_1.2Ni_0.2Mn_0.6O₂ with peculiar layered spinel character dramatically represented increased discharge capacity, improved cycling stability as well as excellent rate capability at high-voltage even up to 5.0 V.     

Coupling of ultrasound‐assisted extraction and expanded bed adsorption for simplified medicinal plant processing and its theoretical model: Extraction and enrichment of ginsenosides from Radix Ginseng as a case study

A high‐efficient and environmental‐friendly method for the preparation of ginsenosides from Radix Ginseng using the method of coupling of ultrasound‐assisted extraction with expanded bed adsorption is described. Based on the optimal extraction conditions screened by surface response methodology, ginsenosides were extracted and adsorbed, then eluted by the two‐step elution protocol. The comparison results between the coupling of ultrasound‐assisted extraction with expanded bed adsorption method and conventional method showed that the former was better than the latter in both process efficiency and greenness. The process efficiency and energy efficiency of the coupling of ultrasound‐assisted extraction with expanded bed adsorption method rapidly increased by 1.4‐fold and 18.5‐fold of the conventional method, while the environmental cost and CO₂ emission of the conventional method were 12.9‐fold and 17.0‐fold of the new method. Furthermore, the theoretical model for the extraction of targets was derived. The results revealed that the theoretical model suitably described the process of preparing ginsenosides by the coupling of ultrasound‐assisted extraction with expanded bed adsorption system.     

Liquid chromatographic resolution of racemic rasagiline and its analogues on a chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid

A liquid chromatographic chiral stationary phase based on (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid was applied to the resolution of 15 analytes, including racemic rasagiline, a chiral drug for the treatment of Parkinson's disease, and its analogues. The composition of mobile phase was optimized to be ethanol/acetonitrile/acetic acid/triethylamine (80:20:0.2:0.3, v/v/v/v) by evaluating the chromatographic results for the resolution of five selected analytes under various mobile phase conditions. Under the optimized mobile phase conditions, racemic rasagiline was resolved quite well with a separation factor of 1.48 and resolution of 2.71 and its 14 analogues were also resolved reasonably well with separation factors of 1.06–1.54 and resolutions of 0.54–2.11. Among 15 analytes, racemic rasagiline was resolved best except for just one analyte. The analyte structure–enantioselectivity relationship indicated that racemic rasagiline has the most appropriate structural characteristics for resolution on the chiral stationary phase.     

Solid-Liquid Phase Transfer Catalytic Synthesis XII

The anion derived from diethyl malonate reacts with a series of halides readly under microwave irradiation, and the isolated yield of alkylated products varying from 64% to 86%.     

The Reaction of Ninhydrin with Trimethylbenzenes under Friedel-Crafts Reaction Conditions

The reaction of ninhydrin with 1,2,3- and 1,2,4-trimethylbenzene in the presence of H₂SO₄ or AlCl₃ afforded 2-monoaryl and 2,2-diaryl-1,3-indanedione derivatives as the major products. With 1,3,5-trimethylbenzene as the arene nucleophile, either a reduction product or an indenoindanone derivative was obtained depending upon the catalyst employed in the reaction.     

Asymmetric Syntheses XXVI: Catalytic Enantioselective Syntheses of β-Hydroxy Esters via Double Chiral Induction in Asymmetric Reformatsky Reactions

Catalytic asymmetric Reformatsky reactions of benzaldehyde with optically active menthyl bromoacetates in the presence of Zn-Cu couple were performed using 0.25 equiv. of (1R,2S) or (1S,2R)-dimethyl-2-amino-1,2-diphenyl ethanol as chiral ligand to obtain β - hydroxy esters with enantioselectivities up to 60.2%. The obvious double chiral induction effect was observed while chiral ligands matched with optically active substrates.     

Release Property of Alginate Beads Coated with Poly(N-isopropylacrylamide-co-dimethylaminoethylmethacrylate)

Alginate beads were coated with copolymers of N-isopropylacrylamide and dimethylaminoethylmethacrylate (P(NIPAM-co-DMAEMA)s) by taking advantage of electrostatic interaction between alginate and the copolymer. The copolymers, of which DMAEMA contents in the feed for the copolymerization were 5.0% (PND 5) and 15.0% (PND 15), were employed for the coatings of alginate beads. The adsorption curve of PND 5 and PND 15 on the surface of alginate beads seemed to be Langmuir isotherm. The beads were coated in the PND solutions (2%, pH 5.0 or pH 7.0) and the amounts of adsorption (g PND/g alginate) were about 1.3 with PND 5 solution (pH 5.0), 1.2 with PND 15 solution (pH 5.0), and 0.75 with PND 15 (pH 7.0). The release from the beads coated with PNDs were observed at 30°C, 37°C, and 45°C using amaranth or FITC-dextran as a dye. The degrees of release were significantly suppressed due to the coating layers of PNDs. However, the coating layers could hardly act as a controller for the temperature-sensitive release.     

Spectral characterisation of new organic fluorescent dyes with an alkoxysilane moiety and their utilisation for the labelling of layered silicates

New fluorescence dyes with an alkoxysilane moiety were synthesised by the condensation of 3-(triethoxysilyl)-1-propanamine (3-aminopropyltriethoxysilane) with 4,10-benzothioxanthene-3,1′-dicarboxylic acid anhydride (BTXA) and N,N-dimethylaminonaphthalene-1,8-dicarboxylic acid anhydride (DMANA), which was accompanied by the formation of an imidic bridge. The compounds N-(3-(triethoxysilyl)propyl)-thioxantheno[2,1,9-dej]isoquinoline-1,3-dione (BTX-S) and 4-(N′, N′-dimethyl)-N-(triethoxysilyl)propyl-1,8-naphthalene dicarboxylic acid imide (DMAN-S) were characterised by steady-state and time-resolved fluorescence spectroscopy in chloroform and ethanol. Both conjugates (BTX-S and DMAN-S) exhibited absorption and emission bands in the same region as the un-substituted BTXA and DMANA. An important Stokes shift was observed for DMAN-S in ethanol. A high fluorescence quantum yield was observed for BTX-S in both solvents and for DMAN-S in chloroform. In addition, the newly developed fluorescent silane dyes were covalently attached to the microscopic particles of layered silicates and on the surface of SiO₂ wafers as a proof of concept for fluorescence particle (surface) visualisation. The surface wafer modification was precisely characterised by X-ray photoelectron spectroscopy (XPS). Successful covalent linkage onto the particles of layered silicates was proved by confocal laser scanning microscopy technique.