Hebei University is the only Comprehensive University in Hebei which is directly under Hebei provincial government and the Ministry of Education, China. It's located in Baoding, Hebei Province, China. The university currently has an enrollment of 44,200, including 5500 graduates and 38,700 undergraduates. 169 international students are also studying at the university. Wikipedia.
Yan H.,Hebei University
Journal of chromatography. A | Year: 2013
Dispersive liquid-liquid microextraction (DLLME) is a modern sample pretreatment technique that is regarded as consilient with the current trends of modern analytical chemistry. DLLME is simple, inexpensive, environmentally friendly, and could offer high enrichment factors from a wide gap between acceptor and donor phases. As a consequence, DLLME has attracted considerable attention from researchers and, based on the numerous publications concerning DLLME, has been generally accepted in separation science since the technique's invention in 2006. However, several innate weaknesses of DLLME, which restrict the technique's use in certain fields, have led to various attempts or suggestions to improve this technique. The present review focuses on the recent advances made in DLLME; the selected papers that are discussed in this work represent modifications that fall into three main categories (exploration of new extraction solvents, disperser solvents and combination with other techniques). The recent applications of DLLME in environmental, food and biological samples are also summarised, covering almost all of the publications related to the technology from the beginning. In addition, the feasibility of future trends of DLLME is discussed. Copyright © 2013 Elsevier B.V. All rights reserved.
Zhang C.,CAS Changchun Institute of Applied Chemistry |
Zhang C.,Hebei University |
Lin J.,CAS Changchun Institute of Applied Chemistry
Chemical Society Reviews | Year: 2012
Luminescent materials have found a wide variety of applications, including information displays, lighting, X-ray intensification and scintillation, and so on. Therefore, much effort has been devoted to exploring novel luminescent materials so far. In the past decade, defect-related luminescent materials have inspired intensive research efforts in their own right. This kind of luminescent material can be basically classified into silica-based materials, phosphate systems, metal oxides, BCNO phosphors, and carbon-based materials. These materials combine several favourable attributes of traditional commercially available phosphors, which are stable, efficient, and less toxic, being free of the burdens of intrinsic toxicity or elemental scarcity and the need for stringent, intricate, tedious, costly, or inefficient preparation steps. Defect-related luminescent materials can be produced inexpensively and on a large scale by many approaches, such as sol-gel process, hydro(solvo)thermal reaction, hydrolysis methods, and electrochemical methods. This review article highlights the recent advances in the chemical synthesis and luminescent properties of the defect-related materials, together with their control and tuning, and emission mechanisms (solid state physics). We also speculate on their future and discuss potential developments for their applications in lighting and biomedical fields. This journal is © The Royal Society of Chemistry 2012.
Zhang Z.,Hebei University
Information Sciences | Year: 2012
Study mainly investigates generalized intuitionistic fuzzy (IF) rough sets based on IF coverings. By using an IF covering, an IF triangular norm, and an IF implicator, two pairs of generalized lower and upper IF rough approximation operators have been constructed, and some fundamental properties are examined. Then, we give some conditions under which the generalized lower IF rough approximation operator is an IF interior operator and the generalized upper IF rough approximation operator is an IF closure operator. Furthermore, the duality of the generalized IF rough approximation operators is discussed. In addition, we propose some concepts and conditions for two intuitionistic coverings to generate an identical lower IF rough approximation operator and an identical upper IF rough approximation operator with the purpose of removing the redundancy in an IF covering. Finally, we compare the IF-neighborhood-oriented IF rough approximation operators with IF-neighborhood-operator-oriented IF rough approximation operators and obtain the conditions under which some or all of these approximation operators are equivalent. © 2012 Elsevier Inc. All rights reserved.
Zhang Z.,Hebei University
Information Fusion | Year: 2013
In this paper, we extend the power geometric (PG) operator and the power ordered weighted geometric (POWG) operator [Z.S. Xu, R.R. Yager, Power-geometric operators and their use in group decision making, IEEE Transactions on Fuzzy Systems 18 (2010) 94-105] to Atanassov's intuitionistic fuzzy environments, i.e., we develop a series of generalized Atanassov's intuitionistic fuzzy power geometric operators to aggregate input arguments that are Atanassov's intuitionistic fuzzy numbers (IFNs). Then, we study some desired properties of these aggregation operators and investigate the relationships among these operators. Furthermore, we apply these aggregation operators to develop some methods for multiple attribute group decision making with Atanassov's intuitionistic fuzzy information. Finally, two practical examples are provided to illustrate the proposed methods. © 2013 Elsevier B.V. All rights reserved.
Yu W.,Hebei University
Journal of Alloys and Compounds | Year: 2013
The evolution of photoluminescence (PL) from Si cluster to nanocrystal in Si-rich oxide (SRO)/SiO2 multilayer films is reported. Two PL bands can be obtained when the SRO layer thickness is no larger than 2 nm, and the high energy PL band (blue band) is related to the interband transition of Si cluster caused by quantum confinement effect (QCE), while the low energy band (red band) is related to the interface recombination. Both Si clusters and nanocrystals exist in the film when the SRO layer is increased to 3 nm, and the intense PL in the red band suggests that Si nanocrystals becomes the main light-emitting centers. The blue band disappears when the SRO layer is increased to 4 nm, and the PL mechanisms of the red band are QCE and interface defects in Si nanocrystals. © 2013 Elsevier B.V. All rights reserved.