城市燃气事故原因透析

介绍了近年来发生的多起燃气事故,对城市燃气的性质特点进行了分析,从管道燃气、瓶装燃气、人为因素等方面详尽的阐述了城市燃气火灾事故原因,详细说明了确保安全用气的具体措施.     

Facile synthesis of metal-organic frameworks embedded in interconnected macroporous polymer as a dual acid-base bifunctional catalyst for efficient conversion of cellulose to 5-hydroxymethylfurfural

5-Hydroxymethylfurfural (5-HMF), as a key platform compound for the conversion of biomass to various biomass-derived chemicals and biofuels, has been attracted extensive attention. In this research, using Pickering high internal phase emulsions (Pickering HIPEs) as template and functional metal-organic frameworks (MOFs, UiO-66-SO₃H and UiO-66-NH₂)/Tween 85 as co-stabilizers to synthesis the dual acid-base bifunctional macroporous polymer catalyst by one-pot process, which has excellent catalytic activity in the cascade reaction of converting cellulose to 5-HMF. The effects of the emulsion parameters including the amount of surfactant (ranging from 0.5% to 2.0% (mass)), the internal phase volume fraction (ranging from 75% to 90%) and the acid/base Pickering particles mass ratio (ranging from 0:6 to 6:0) on the morphology and catalytic performance of solid catalyst were systematically researched. The results of catalytic experiments suggested that the connected large pore size of catalyst can effectively improve the cellulose conversion, and the synergistic effect of acid and base active sites can effectively improve the 5-HMF yield. The highest 5-HMF yield, about 40.5%, can be obtained by using polymer/MOFs composite as catalyst (Poly-P12, the pore size of (53.3 ±11.3) μm, the acid density of 1.99 mmol·g^-1 and the base density of 1.13 mol·g^-1) under the optimal reaction conditions (130 ℃, 3 h). Herein, the polymer/MOFs composite with open-cell structure was prepared by the Pickering HIPEs templating method, which provided a favorable experimental basis and theoretical reference for achieving efficient production of high added-value product from abundant biomass.     

Utilization of waste vanadium-bearing resources in the preparation of rare-earth vanadate catalysts for semi-hydrogenation of α,β-unsaturated aldehydes

Recycling industrial solid waste not only saves resources but also eliminates environmental concerns of toxic threats. Herein, we proposed a new strategy for the utilization of petrochemical-derived carbon black waste, a waste vanadium-bearing resource (V > 30000 ppm (10 ⁻⁶)). Chemical leaching was employed to extract metallic vanadium from the waste and the leachate containing V was used as an alternative raw material for the fabrication of vanadate nanomaterials. Through the screening of various metal cations, it was found that the contaminated Na⁺ during the leaching process showed strong competitive coordination with the vanadium ions. However, by adding foreign Ce³⁺ and Y³⁺ cations, two rare-earth vanadates, viz., flower-like CeVO₄ and spherical YVO₄ nanomaterials, were successfully synthesized. Characterization techniques such as scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, Fourier-transform infrared, and N₂ physisorption were applied to analyze the physicochemical properties of the waste-derived nanomaterials. Importantly, we found that rare-earth vanadate catalysts exhibited good activities toward the semi-hydrogenation of α,β-unsaturated aldehydes. The conversion of cinnamaldehyde and cinnamic alcohol selectivity were even higher than those of the common CeVO₄ prepared using pure chemicals (67.2% vs. 27.7% and 88.4% vs. 53.5%). Our work provides a valuable new reference for preparing vanadate catalysts by the use of abundant vanadium-bearing waste resources.     

A pilot study on ^99mTc-3PRGD2 scintigraphy in diagnosis of brain glioma

The ^99mTc-3PRGD₂ targeted SPECT/CT scanning was of significance in detecting differentiated glioma.In this work,the diagnostic value of ^99mTc-3PRGD₂ scintigraphy in brain glioma was evaluated by the ten clinically verified brain glioma patients after obtaining informed consent.The patients first accepted X-ray imaging to localize the detecting regions before administrating with ^99mTc-3PRGD₂ at a mean radioactivity of 849±115 MBq via single intravenous bolus injection 2 h prior to SPECT/CT imaging.Tumor samples for detectingαvβ3 were collected by surgical operations two weeks after the scintigraphy.The results of CT and SPECT scanning were merged and compared.The correlation between tumor occupation（T/N ratio） andαvβ3 expression level were analyzed.The T/N ratios in brain glioma were proportionally correlated to av(33 positive cell percentage（R²=0.9253,p<0.05）.This study primarily evaluated the clinical application of ^99mTc-3PRGD₂ SPECT scintigraphy on brain glioma.The more pathological types and detecting strategies covering a large amount of samples would aid to clarify the potentials.     

Synthesis, structure and catalytic behavior of ytterbium complexes bearing a phenoxy（quinolinyl）amide ligand

Two ytterbium complexes stabilized by phenoxy(quinolinyl)amide ligand 3,5-Bu t 2 -2-OC 6 H 2 CH 2 N-8-C 9 H 6 N (L) were synthesized and characterized. Reaction of anhydrous YbCl 3 with 1 equiv. of LLi 2 in THF gave the ytterbium chloride [LYbCl(THF)] 2 (1) in 73% yield. A further reaction of complex 1 with equimolar of NaN(SiMe 3 ) 2 in THF afforded the unexpected heterobimetallic "ate"-complex L 2 YbNa(THF) 2 (2) via a ligand redistribution reaction. Complex 2 could also be prepared in high isolated yield by the reaction of anhydrous YbCl 3 with 2 equiv. of LNa 2 generated in situ. Both complexes 1 and 2 were characterized by IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction analysis. It was found that complex 2 was an effective catalyst for the addition reaction of aromatic amines to carbodiimides.     

Properties of the ν7/2-[503]（f7/2） band in 185Pt

High-spin states in 185Pt have been reinvestigated via the reaction 173Yb（16O, 4n） at a beam energy of 90 MeV. The previously known band based on the ν7/2-[503]（f7/2） Nilsson orbital has been extended to higher spin states. Properties of the ν7/2-[503]（f7     

Effect of Microstructure on Corrosion Fatigue Behavior of 1500 MPa Level Carbide-Free Bainite/Martensite Dual-Phase High Strength Steel

  Influence of microstructure of the experimental steels on the corrosion fatigue behavior in 35% of NaCl aqueous solution was studied. Experimental results show that compared with the full martensite (FM) steel, the carbide free bainite/martensite (CFB/M) steel has higher corrosion fatigue strength and corrosion fatigue crack threshold (ΔKthcf), and lower corrosion crack propagation rate [(da/dN)cf].     

Pre-stack inversion for caved carbonate reservoir prediction: A case study from Tarim Basin, China

The major storage space types in the carbonate reservoir in the Ordovician in the TZ45 area are secondary dissolution caves.For the prediction of caved carbonate reservoir,post-stack methods are commonly used in the oilfield at present since pre-stack inversion is always limited by poor seismic data quality and insufficient logging data.In this paper,based on amplitude preserved seismic data processing and rock-physics analysis,pre-stack inversion is employed to predict the caved carbonate reservoir in TZ45 area by seriously controlling the quality of inversion procedures.These procedures mainly include angle-gather conversion,partial stack,wavelet estimation,low-frequency model building and inversion residual analysis.The amplitude-preserved data processing method can achieve high quality data based on the principle that they are very consistent with the synthetics.Besides,the foundation of pre-stack inversion and reservoir prediction criterion can be established by the connection between reservoir property and seismic reflection through rock-physics analysis.Finally,the inversion result is consistent with drilling wells in most cases.It is concluded that integrated with amplitude-preserved processing and rock-physics,pre-stack inversion can be effectively applied in the caved carbonate reservoir prediction.     

Effect of ultrasonic field treatment on degassing of 2024 alloy

The 2024 aluminum alloy was prepared with different ultrasonic processes. Effects of ultrasonic treatment parameters including ultrasonic power, treatment time, treatment temperature, and frequency resonance, as well as C₂Cl₆ degasser on degassing of the 2024 aluminum alloy were investigated. Results indicate that increasing ultrasonic power at the same ultrasonic treatment time can improve the degassing effect. The optimum degassing efficiency can be obtained under the resonant ultrasound condition. With the combination of 1% C₂Cl₆ addition and 150 W ultrasonic treatment for 40 s, the hydrogen content of the alloy is decreased by 52.9%. At the same time, the tensile strength and elongation are increased by 28.3% and 92.3%, respectively, and the yield strength is slightly increased by 6.7%. The degassing mechanism is also discussed.

     

Cryptanalysis of Full-Round Magpie Block Cipher

Magpie is a lightweight block cipher proposed by Li et al. in Acta Electronica Sinica volumn 45,issue 10. It adopts an substitution-permutation network(SPN) structure with a block size of 64 bits and the key size of 96 bits, respectively. To achieve the consistency of the encryption and decryption, which is both hardware and software friendly, 16 bits of the key are used as control signals to select S-boxes and another 16 bits of the key are used to determine the order of the operations. As the ...