Structure,trend and prospect of operational research: a scientific analysis for publications from 1952 to 2020 included in Web of Science database

As an important research direction, operational research (OR) has always attracted scholars worldwide. We study the structure, trend and prospect in the OR field by conducting a bibliometric analysis of publications in the period of 1952–2020, which are included in the Web of Science (WoS) database. Using three effective bibliometric tools, namely, VOS viewer, CiteSpace, and Bibliometrix, a total of 5,353 publications were retrieved to show clear visual results using a series of scientific analyses. First, a performance analysis revealed the basic characteristics of publications considering the type distribution, annual trend, quantity and quality. Then, a cooperation analysis presented the influential countries/regions and showed the relationships among countries/regions, institutions and authors during different periods based on bibliometric indicators and co-authorship networks. Moreover, a keyword analysis was conducted to investigate the hot topics and development of the OR field, using co-occurrence analysis, timeline view analysis and evolution analysis. Finally, we discussed the implications and limitations, and summarized the main findings. This study hopes to provide important and valuable references for future research on the OR field.

     

STUDIES OF MULTICOMPONENT COMPLEX OXIDE CATALYSTS FOR OXIDATIVE COUPLING OF METHANE VI.SURFACE BASICITY AND SURFACE ACTIVE OXYGEN SPECIES OF LiTi_xLa_(1-x)O_2 λ MULTICOMPONENT OXIDE CATALYSTS

The surface basicity of Ti-La-Li multicoinponent oxides has been investigated by means of CO2-TPD. The experiment results show that C2 (C2H6 C2H4) selectivity is related to surface basic strength. The surface active oxygen species have also been characterized by means of XPS, O2-TPD and so on. It has been indicated that C2 selectivity and CH4 conversion are correlated with lattice oxygen and the adsorbed oxygen on the surface of the catalyst respectively In the O2-TPD experiments, it has also been found that there are three kinds of oxygen species on the surface of the series catalvsts, which are a (100℃ 750℃) Among them α-oxvgen causes deep oxidation whileβand γ oxygen species are related to oxidalive coupling of methane (OCM).     

Sorption of 241Am by Aspergillus nigerspore and hyphae

Biosorption of ²⁴¹Am by a fungus A. niger, including the spore and hyphae, was investigated. The preliminary results showed that the adsorption of ²⁴¹Am by the microorganism was efficient. More than 96% of the total ²⁴¹Am could be removed from ²⁴¹Am solutions of 5.6-111 MBq/l (C _o) by spore and hyphaeof A. niger, with adsorbed ²⁴¹Am metal (Q) of 7.2-142.4 MBq/g biomass, and 5.2-106.5 MBq/g, respectively. The biosorption equilibrium was achieved within 1 hour and the optimum pH range was pH 1-3. No obvious effects on ²⁴¹Am adsorption by the fungus were observed at 10-45 °C, or in solutions containing Au³⁺ or Ag⁺, even 2000 times above the ²⁴¹Am concentration. The ²⁴¹Am biosorption by the fungus obeys the Freundlich adsorption equation. There was no significant difference between the adsorption behavior of A. nigerspore and hyphae. This revised version was published online in July 2006 with corrections to the Cover Date.     

Effect of PEG on the crystallization of PPDO/PEG blends

A new biodegradable polymer system, poly(p-dioxanone) (PPDO)/poly(ethylene glycol) (PEG) blend was prepared by a solvent casting method using chloroform as a co-solvent. The PPDO/PEG blends have different weight ratios of 95/5, 90/10, 80/20 and 70/30. Crystallization of homopolymers and blends were investigated by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD). When 5% of PEG was blended, the crystallization exothermal peaks (T_c) of PPDO increased sharply and the crystallization exothermal peaks (T_c) of PEG decreased slightly compared with the homopolymers. The crystallization rates of both components increased, and caused greater relative crystallization degree (X_t%). But when the content of PEG was more than 5%, the crystalline behaviors of blends had no more significant changes accordingly. The melting points of each sample varied little over the entire composition range in this study. The nonisothermal crystallization of PPDO homopolymer and blend (PPDO/PEG = 70/30) were also studied by DSC. The crystallization began at a higher temperature when the cooling rates were slower. The nonisothermal crystallization kinetics of blends was analyzed by Ozawa equation. The results showed that the Ozawa equation failed to describe the whole crystallization of the blend, but Mo equation could depict the nonisothermal crystallization perfectly.     

Neutron activation analysis of gold and iridium in steel

A method of determination of trace gold and iridium in steel is presented. The samples were preconcentrated with an anion exchanger. The chemical recoveries were determined by an isotope tracer technique using¹⁹⁸Au and¹⁹²Ir.     

Improved results on the robustness of stochastic approximation algorithms

This paper is a continuation of the research carried out in [1]–[2], where the robustness analysis for stochastic approximation algorithms is given for two cases: 1. The regression function and the Liapunov function are not zero at the sought-forx ⁰; 2. lim sup _n a131_{n i=1} ⁿ _i+1 is not zero, where { _i } are the measurement errors and {a _n} are the weighting coefficients in the algorithm. Allowing these deviations from zero to occur simultaneously but to remain small, this paper shows that the estimation error is still small even for a class of measurement errors more general than that considered in [2].This project is supported by the National Natural Science Foundation of China.     

Dynamic Deformation of Frozen Soil at a High Strain Rate:Experiments and Damage-Coupled Constitutive Model

The dynamic compressive deformation of frozen soil was investigated by conduct-ing the split-Hopkinson pressure bar (SHPB) experiments at three temperatures and...     

Effect of graft polymer prepared by living radical polymerisation on electro-optical properties of polymer dispersed liquid crystal

In this study, a graft polymer matrix prepared by living radical polymerisation had been incorporated into polymer dispersed liquid crystals (PDLCs). The electro-optical properties of the PDLCs were investigated. The results showed that the length and density of graft chain had a great influence on the memory effect of the PDLCs. Low-driving-voltage and weak-memory-effect PDLCs could easily be obtained with a graft polymer matrix.     

Highly efficient toughening effect of ultrafine full-vulcanized powdered rubber on poly(lactic acid)(PLA)

A unique ultrafine full-vulcanized powdered ethyl acrylate rubber (EA-UFPR) was used as the toughening modifier for poly (lactic acid) (PLA). Largely improved tensile toughness was successfully achieved with the incorporation of only 1 wt% EA-UFPR, while the tensile strength and modulus of the blends were almost the same as pure PLA. The highly efficient toughening of PLA by UFPR is mainly ascribed to the strong interfacial interaction between PLA and UFPR and good dispersion of UFPR particles in PLA matrix. Our work provides an effective toughening method to largely improve the mechanical properties of PLA without sacrificing its stiffness, which is very important for the wide application of PLA materials.     

Application of wavelet transform in-ray spectra analysis

The frequency distribution of different ingredients in-ray spectra,e.g.,photo-peak,fluctuations of counts and Compton region,is separately analyzed.After wavelet transform of-ray spectra,the wavelet coefficients of a photo-peak increase with transforming scales and these coefficients show direct proportion with intensity of peak at determinate scale.A novel algorithm based on wavelet transform is proposed and studied.The results indicate that most of the photo-peaks in multi-spectra can be determined accurately,the-rays energy and intensity of the peak can also be determined.This method has the prospect of being applied in on-line multi-spectra analysis in such fields as radioprotection and nuclear safety monitoring.