The analytic response theory at density functional theory level is applied to investigate onephoton and two-photon absorption properties of a series of recently synthesized pyrene-core derivatives. The theoretical res...The analytic response theory at density functional theory level is applied to investigate onephoton and two-photon absorption properties of a series of recently synthesized pyrene-core derivatives. The theoretical results show that there are a few charge-transfer states for each compound in the lower energy region. The one-photon absorption properties of the five investigated compounds are highly consistent with those given by experimental measurements. The two-photon absorption intensities of the compounds are greatly enhanced with the increments of the molecular sizes, in which the two-photon absorption cross section of the four-branched compound is about 5.6 times of that of the mono-branched molecule. Fhrthermore, it is shown that the two-photon absorption properties are sensitive to the geometrical arrangements.展开更多
Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives.In this work,we conducted a computational study of two com...Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives.In this work,we conducted a computational study of two competitive mechanisms in which the carbon atom of acetylene or carbon monoxide attacked and inserted from two different directions of the six-membered ring reactant to clarify the principle characteristics of this transformation.The calculation results reveal that:(i)the insertion process of alkyne or carbon monoxide is the key step of the reaction;(ii)for the(5+2)cycloaddition reaction of acetylene,higher energy is required to break the Rh−O bond of the reactant,and the reaction tends to complete the insertion from the side of the Rh−C bond;(iii)for the(5+1)cycloaddition of carbon monoxide,both reaction paths have lower activation free energy,and the two will generate a competition mechanism.展开更多
In order to improve the safety properties of an offloading system with side-by-side （SBS） mooring in which the FPSO is moored by a yoke system in the field of BZ25-1, it is necessary to analyze those properties. Acc...In order to improve the safety properties of an offloading system with side-by-side （SBS） mooring in which the FPSO is moored by a yoke system in the field of BZ25-1, it is necessary to analyze those properties. According to the experience of similar projects, tow strategies of different offioading arrangements were discussed by using the 3-D radiation/diffraction theory and quasi-static time domain method to assess their respective safety properties. Through the safety assessment analysis of different arrangement comparisons, various ways to improve the safety properties of off＇loading systems with side-by-side mooring were verified by analyzing the tension in the mooring lines and the fender deflection. Through comparison it can be concluded that by enlarging the key factors properly, including the size of the fenders and the hawsers as well as the number of hawsers, a better safety performance can be achieved.展开更多
Ionic liquids （ILs） have attracted many attentions in the dissolution of cellulose due to their unique physicochemical properties as green solvents. However, the mechanism of dissolution is still under debate. In th...Ionic liquids （ILs） have attracted many attentions in the dissolution of cellulose due to their unique physicochemical properties as green solvents. However, the mechanism of dissolution is still under debate. In this work, computational investigation for the mechanisms of dissolution of cellulose in [Bmim]Cl, [Emim]C1 and [Emim]OAc ILs was performed, and it was focused on the process of breakage of cellulose chain and ring opening using cellobiose as a model molecule. The detailed mechanism and reaction energy barriers were computed for various possible pathways by density functional theoretical method. The key finding was that 1Ls catalyze the dissolution process by synergistic effect of anion and cation, which led to the cleavage of cellulose chain and formation of derivatives of cellulose. The investigation on ring opening process ofcellobiose suggested that carbene formed in ILs played an important role in the side reaction of cellulose, and it facilitated the formation of a covalent bond between cellulose and imidazolium core. These computation results may provide new perspective to understand and apply ILs for pretreatment of cellulose.展开更多
The objective of this article was to analyze the poultry and derivatives commerce between Brazil and China, taking into account the current market and the perspectives for the next years. The method used was the bibli...The objective of this article was to analyze the poultry and derivatives commerce between Brazil and China, taking into account the current market and the perspectives for the next years. The method used was the bibliographic review and analysis of secondary data from different sources, associated with the Market Orientation Theory and the Value Chain Theory. Nowadays, China is Brazil＇s main commercial partner in the international market, but taking into account the chicken meat and its derivatives, having Brazil as the first worldwide exporter and China, the second largest consumer, an effective commercial relationship has not been established yet. To understand the poultry market exchanges between Brazil and China, a framework was built to demonstrate the characteristics and factors found to influence country negotiations, considering current reality and future perspectives. Considering the Theory of Market Orientation, it is concluded that Brazil has effective conditions to consolidate itself as a major supplier of chicken meat and derivatives to China, because it shows determinant characteristics and market factors that allows the association of the national poultry value chain to the demands of the Chinese consumers, but some adjustments are needed in the sphere of international politics.展开更多
The Noether and Lie symmetries as well as the conserved quantities of Hamiltonian system with fractional derivatives are es-tablished. The definitions and criteria for the fractional symmetrical transformations and qu...The Noether and Lie symmetries as well as the conserved quantities of Hamiltonian system with fractional derivatives are es-tablished. The definitions and criteria for the fractional symmetrical transformations and quasi-symmetrical transformations inthe Noether sense of Hamiltonian system are first discussed. Then, using the invariance of Hamiltonian action under the infini-tesimal transformations with respect to time, generalized coordinates and generalized momentums, the fractional Noethertheorem of the system is obtained. Further, the Lie symmetry and conserved quantity of the system are acquired. Two exam-ples are presented to illustrate the application of the results.展开更多
文摘The analytic response theory at density functional theory level is applied to investigate onephoton and two-photon absorption properties of a series of recently synthesized pyrene-core derivatives. The theoretical results show that there are a few charge-transfer states for each compound in the lower energy region. The one-photon absorption properties of the five investigated compounds are highly consistent with those given by experimental measurements. The two-photon absorption intensities of the compounds are greatly enhanced with the increments of the molecular sizes, in which the two-photon absorption cross section of the four-branched compound is about 5.6 times of that of the mono-branched molecule. Fhrthermore, it is shown that the two-photon absorption properties are sensitive to the geometrical arrangements.
基金This work was supported by the Natural Science Foundation of Gansu Province(20JR5RA479)the Outstanding Youth Research Program of Lanzhou University of Arts and Sciences(2018JCQN008).
文摘Rhodium-catalyzed cycloaddition reaction was calculated by density functional theory M06-2X method to directly synthesize benzoxepine and coumarin derivatives.In this work,we conducted a computational study of two competitive mechanisms in which the carbon atom of acetylene or carbon monoxide attacked and inserted from two different directions of the six-membered ring reactant to clarify the principle characteristics of this transformation.The calculation results reveal that:(i)the insertion process of alkyne or carbon monoxide is the key step of the reaction;(ii)for the(5+2)cycloaddition reaction of acetylene,higher energy is required to break the Rh−O bond of the reactant,and the reaction tends to complete the insertion from the side of the Rh−C bond;(iii)for the(5+1)cycloaddition of carbon monoxide,both reaction paths have lower activation free energy,and the two will generate a competition mechanism.
基金Supported by the China National 111 project under Grant No.B07019Important National Science & Technology Specific Projects under Grant No.2008ZX05-056-03
文摘In order to improve the safety properties of an offloading system with side-by-side （SBS） mooring in which the FPSO is moored by a yoke system in the field of BZ25-1, it is necessary to analyze those properties. According to the experience of similar projects, tow strategies of different offioading arrangements were discussed by using the 3-D radiation/diffraction theory and quasi-static time domain method to assess their respective safety properties. Through the safety assessment analysis of different arrangement comparisons, various ways to improve the safety properties of off＇loading systems with side-by-side mooring were verified by analyzing the tension in the mooring lines and the fender deflection. Through comparison it can be concluded that by enlarging the key factors properly, including the size of the fenders and the hawsers as well as the number of hawsers, a better safety performance can be achieved.
基金Supported by the National Natural Science Foundation of China(21210006,21276255,21406230,91434111)the Natural Science Foundation of Beijing of China(2131005,2142029)
文摘Ionic liquids （ILs） have attracted many attentions in the dissolution of cellulose due to their unique physicochemical properties as green solvents. However, the mechanism of dissolution is still under debate. In this work, computational investigation for the mechanisms of dissolution of cellulose in [Bmim]Cl, [Emim]C1 and [Emim]OAc ILs was performed, and it was focused on the process of breakage of cellulose chain and ring opening using cellobiose as a model molecule. The detailed mechanism and reaction energy barriers were computed for various possible pathways by density functional theoretical method. The key finding was that 1Ls catalyze the dissolution process by synergistic effect of anion and cation, which led to the cleavage of cellulose chain and formation of derivatives of cellulose. The investigation on ring opening process ofcellobiose suggested that carbene formed in ILs played an important role in the side reaction of cellulose, and it facilitated the formation of a covalent bond between cellulose and imidazolium core. These computation results may provide new perspective to understand and apply ILs for pretreatment of cellulose.
文摘The objective of this article was to analyze the poultry and derivatives commerce between Brazil and China, taking into account the current market and the perspectives for the next years. The method used was the bibliographic review and analysis of secondary data from different sources, associated with the Market Orientation Theory and the Value Chain Theory. Nowadays, China is Brazil＇s main commercial partner in the international market, but taking into account the chicken meat and its derivatives, having Brazil as the first worldwide exporter and China, the second largest consumer, an effective commercial relationship has not been established yet. To understand the poultry market exchanges between Brazil and China, a framework was built to demonstrate the characteristics and factors found to influence country negotiations, considering current reality and future perspectives. Considering the Theory of Market Orientation, it is concluded that Brazil has effective conditions to consolidate itself as a major supplier of chicken meat and derivatives to China, because it shows determinant characteristics and market factors that allows the association of the national poultry value chain to the demands of the Chinese consumers, but some adjustments are needed in the sphere of international politics.
基金supported by the National Natural Science Foundation of China (Grant No. 11072218)
文摘The Noether and Lie symmetries as well as the conserved quantities of Hamiltonian system with fractional derivatives are es-tablished. The definitions and criteria for the fractional symmetrical transformations and quasi-symmetrical transformations inthe Noether sense of Hamiltonian system are first discussed. Then, using the invariance of Hamiltonian action under the infini-tesimal transformations with respect to time, generalized coordinates and generalized momentums, the fractional Noethertheorem of the system is obtained. Further, the Lie symmetry and conserved quantity of the system are acquired. Two exam-ples are presented to illustrate the application of the results.
