Reduced graphene oxide(RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which...Reduced graphene oxide(RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which include thermal and chemical reduction with ethylene glycol, KOH and Fe powder. The changes in microstructure and surface chemistry of RGOs were extensively characterized by SEM, TEM, AFM, XRD, XPS and Raman spectrum. The results show that significant exfoliation occurs during oxidation and is retained in reduction processes, along with the formation of curled wavy morphology. Compared with large d spacing(0.852 nm) of graphene oxide(GO), the(002) plane distance decreases to 0.358-0.384 nm of RGOs, indicating efficient tuning of surface functionalities through mild reduction methods. The ID/IG ratio of RGOs is about 1.0-1.15, indicating that reconstructed sp^2 domains have smaller sizes and larger quantity. The content of sp^2 bonded C in GO(36.93%, molar fraction) increases to 45.48%-72.92%(molar fraction) in RGOs, along with a drastic decrease in hydroxyl and epoxy and minor changes in carbonyl and carboxyl. Thermal reduction or chemical reduction produces RGOs with residual functionalities, which may render different chemical activity and is desirable in various applications.展开更多
In the article, the author presents some arguments concerning the ＂mathematical method issue＂ in modem economics. The author shows why some reasons, according to which we should use mathematics in （economic） theor...In the article, the author presents some arguments concerning the ＂mathematical method issue＂ in modem economics. The author shows why some reasons, according to which we should use mathematics in （economic） theory, are not convincing （they are even tautological）, and what does mathematization have to do with arbitrariness of the orthodox economic theory. The author also shows why using game theory （a mathematical discipline） in modem microeconomics does not yield knowledge and correct explanation of economic situations and phenomena. At the end, the author presents fundamental questions that form the basis of economic science and its qualitative research methods, and shows what their practical relevance is. The purpose of this article is to argue, contrary to common opinion, that there can be an exact and objective science of economic phenomena that does not necessarily use modem mathematical theories or methods to explain these phenomena.展开更多
Considering the attractive interaction between ferromagnet, we propose the model of magnon-pairs, which two magnons with opposite wave vectors in a Heisenberg is suitable for low-temperature environment. A dressed mag...Considering the attractive interaction between ferromagnet, we propose the model of magnon-pairs, which two magnons with opposite wave vectors in a Heisenberg is suitable for low-temperature environment. A dressed magnon is an energy quantum of the magnon-pairs whose energy is a monotonically increasing function of absolute temperature. Based on the model, we re-investigate the excitation mechanism and thermodynamic properties of the Heisenberg ferromagnet. The correction factor e（O） plays an important role in studying the low-temperature properties of a ferromagnet.展开更多
Researching residual oil distribution not only is a difficulty in the world, but also is the pioneering research subject in different fields such as geology, physical geography and reservoir engineering. The modem geo...Researching residual oil distribution not only is a difficulty in the world, but also is the pioneering research subject in different fields such as geology, physical geography and reservoir engineering. The modem geology technique, well logging technology and reservoir engineering technique develops rapidly, which provides favorable conditions for researching residual oil distribution.展开更多
Three-dimensional （3D） copper foams have been formed by electrodeposition at different nitrogen pressures and examined by scanning electron microscopy. The results indicate that an increase in system pressure leads ...Three-dimensional （3D） copper foams have been formed by electrodeposition at different nitrogen pressures and examined by scanning electron microscopy. The results indicate that an increase in system pressure leads to a decrease of the pore size of the copper foam due to the suppressed coalescence of hydrogen bubbles, while the thickness of the copper foam increases with decreasing pressure. Also, the walls around the pores on the copper foam consist of copper dendrites, and the copper dendrites are made up of copper grains with sizes less than 1 l.tm. The average sizes of the copper grains decrease with increasing system pressure. It has been demonstrated that copper foams with controllable 3D structure formed by electrodeposition at different pressures are comparable to those obtained by electrodeposition at normal pressure in the presence of specific additives.展开更多
基金Project(51274248)supported by the National Natural Science Foundation of ChinaProjects(2015DFR50580,2013DFA31440)supported by the International Scientific and Technological Cooperation Program of China
文摘Reduced graphene oxide(RGO) sheets with varied contents and types of oxygenated groups were synthesized by Hummers treatment of natural graphite powders followed by different nontoxic and mild reduction methods, which include thermal and chemical reduction with ethylene glycol, KOH and Fe powder. The changes in microstructure and surface chemistry of RGOs were extensively characterized by SEM, TEM, AFM, XRD, XPS and Raman spectrum. The results show that significant exfoliation occurs during oxidation and is retained in reduction processes, along with the formation of curled wavy morphology. Compared with large d spacing(0.852 nm) of graphene oxide(GO), the(002) plane distance decreases to 0.358-0.384 nm of RGOs, indicating efficient tuning of surface functionalities through mild reduction methods. The ID/IG ratio of RGOs is about 1.0-1.15, indicating that reconstructed sp^2 domains have smaller sizes and larger quantity. The content of sp^2 bonded C in GO(36.93%, molar fraction) increases to 45.48%-72.92%(molar fraction) in RGOs, along with a drastic decrease in hydroxyl and epoxy and minor changes in carbonyl and carboxyl. Thermal reduction or chemical reduction produces RGOs with residual functionalities, which may render different chemical activity and is desirable in various applications.
文摘In the article, the author presents some arguments concerning the ＂mathematical method issue＂ in modem economics. The author shows why some reasons, according to which we should use mathematics in （economic） theory, are not convincing （they are even tautological）, and what does mathematization have to do with arbitrariness of the orthodox economic theory. The author also shows why using game theory （a mathematical discipline） in modem microeconomics does not yield knowledge and correct explanation of economic situations and phenomena. At the end, the author presents fundamental questions that form the basis of economic science and its qualitative research methods, and shows what their practical relevance is. The purpose of this article is to argue, contrary to common opinion, that there can be an exact and objective science of economic phenomena that does not necessarily use modem mathematical theories or methods to explain these phenomena.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10174024 and 10474025
文摘Considering the attractive interaction between ferromagnet, we propose the model of magnon-pairs, which two magnons with opposite wave vectors in a Heisenberg is suitable for low-temperature environment. A dressed magnon is an energy quantum of the magnon-pairs whose energy is a monotonically increasing function of absolute temperature. Based on the model, we re-investigate the excitation mechanism and thermodynamic properties of the Heisenberg ferromagnet. The correction factor e（O） plays an important role in studying the low-temperature properties of a ferromagnet.
文摘Researching residual oil distribution not only is a difficulty in the world, but also is the pioneering research subject in different fields such as geology, physical geography and reservoir engineering. The modem geology technique, well logging technology and reservoir engineering technique develops rapidly, which provides favorable conditions for researching residual oil distribution.
基金supported by the National Natural Science Foundation of China (20776004)the Program for New Century Excellent Talents in University (NCET-08-0710)
文摘Three-dimensional （3D） copper foams have been formed by electrodeposition at different nitrogen pressures and examined by scanning electron microscopy. The results indicate that an increase in system pressure leads to a decrease of the pore size of the copper foam due to the suppressed coalescence of hydrogen bubbles, while the thickness of the copper foam increases with decreasing pressure. Also, the walls around the pores on the copper foam consist of copper dendrites, and the copper dendrites are made up of copper grains with sizes less than 1 l.tm. The average sizes of the copper grains decrease with increasing system pressure. It has been demonstrated that copper foams with controllable 3D structure formed by electrodeposition at different pressures are comparable to those obtained by electrodeposition at normal pressure in the presence of specific additives.
