Random access is a well-known multiple access method for uncoordinated communication nodes.Existing work mainly focuses on optimizing iterative access protocols,assuming that packets are corrupted once they are collid...Random access is a well-known multiple access method for uncoordinated communication nodes.Existing work mainly focuses on optimizing iterative access protocols,assuming that packets are corrupted once they are collided,or that feedback is available and can be exploited.In practice,a packet may still be able to be recovered successfully even when collided with other packets.System design and performance analysis under such a situation,particularly when the details of collision are taken into consideration,are less known.In this paper,we provide a framework for analytically evaluating the actual detection performance in a random temporal multiple access system where nodes can only transmit.Explicit expressions are provided for collision probability and signal to interference and noise ratio(SINR)when different numbers of packets are collided.We then discuss and compare two receiver options for the AP,and provide detailed receiver design for the premium one.In particular,we propose a synchronization scheme which can largely reduce the preamble length.We also demonstrate that system performance could be a convex function of preamble length both analytically and via simulation,as well as the forward error correction(FEC)coding rate.展开更多
The rational design of highly active and stable atomically dispersed M-X4(M=Fe,Co,Ni,etc.,X=C,N)-based catalysts holds promises for wide application in almost all realms of catalysis.Despite great effort in the constr...The rational design of highly active and stable atomically dispersed M-X4(M=Fe,Co,Ni,etc.,X=C,N)-based catalysts holds promises for wide application in almost all realms of catalysis.Despite great effort in the construction of specific M-X4 centers,the possible effect of non-coordinated heteroatoms on the catalytic activity of metal centers has been rarely explored.Herein,we develop a new type of M-X4 catalyst composed of Fe-N4 centers and non-coordinated B heteroatoms(FeNC+B)and find the key role of non-coordinated B adjacent to Fe-N4 centers in tailoring their electron density and final catalytic selectivity.The experimental and theoretical results demonstrated that non-coordinated boron atoms could decrease the electron density of Fe-N4 centers to a suitable level and thus boost the selective production of nitriles from amine oxidation by depressing the formation of imines due to the flattened energy barrier of the reversible conversion of imines back to amines.As a reusable heterocatalyst,the state-of-the-art FeNC+B catalyst provides a turn-over frequency(TOF)value of 21.6 molbenzonitrile·molFe^−1·h^−1(100℃),outpacing that of bench-marked nonnoble-metal-based homogeneous catalyst by a factor of 3.4.展开更多
Urbanization is a comprehensive concept, a trinity process that population urbanization, economic urbanization and space urbanization, is based on the interactions and mutual influences among the in which, people are ...Urbanization is a comprehensive concept, a trinity process that population urbanization, economic urbanization and space urbanization, is based on the interactions and mutual influences among the in which, people are the central and leading players in this process, while economic activities serve as the driving force and space is the carrier-the physical or material setting as well as the product. So the coordination among these processes is crucial for a country or region＇s sustainable development. China is experiencing rapid growth of cities and a surge in urban population, with the basic national condition of many people and little land, which calls for a systematic study of the issue of coordinated urbanization from theoretical, methodological and practical perspectives. Based on the concept of urbanization and non-coordination of urbanization, this article built a quantitative method to identify and evaluate the urbanization and non-coordination of urbanization, and made an empirical analysis in China between 2000 and 2008. The results show that the non-coordination overall level of China＇s urbanization declined during the study period, because population urbanization, economic urbanization, and space urbanization exhibited different trajectories of change. This study also reveals that performance assessment system, household registration system, and urban land expropriation system, etc., are the main affecting factors. At the end, we put forward some suggestions to achieve sustainable development of China＇s urbanization from the aspects of improving the local government＇s obiective function, imolementing the urban plalming svstem, enforcing public particination asnects and so on.展开更多
Several novel pyridine-oxadiazole iridium complexes were synthesized and characterized through X-ray crystallography.The designed iridium.complexes revealed surprisingly high catalytic activity in C-N bondformation of...Several novel pyridine-oxadiazole iridium complexes were synthesized and characterized through X-ray crystallography.The designed iridium.complexes revealed surprisingly high catalytic activity in C-N bondformation of amides and benzyl alcohols with the assistance of non-coordinating anions.In an attempt to achieve borrowing hydrogen reactions of amides with benzyl alcohols,N,N'-(phenylmethylene)dibenzamide products we re unexpectedly isolated under non-coordinating anion conditions,whereas N-benzylbenzamide products were achieved in the absence of non-coordinating anions.The mechanism explorations excluded the possibility of"silver effect"(silver-assisted or bimetallic catalysis)and revealed that the reactivity of iridium catalyst was varied by non-coordinating anions.This work provided a convenient and useful methodology that allowed the iridium complex to be a chemoselective catalyst and demonstrated the first example of non-coordinating-anion-tuned selective C-N bond formation.展开更多
基金supported by National Natural Science Foundation of China (No. 61271236)Major Projects of Natural Science Research of Jiangsu Provincial Universities (No. 17KJA510004)Postgraduate Research & Practice Innovation Program of Jiangsu Province (No. KYCX17_0763, No.KYCX18_0907)
文摘Random access is a well-known multiple access method for uncoordinated communication nodes.Existing work mainly focuses on optimizing iterative access protocols,assuming that packets are corrupted once they are collided,or that feedback is available and can be exploited.In practice,a packet may still be able to be recovered successfully even when collided with other packets.System design and performance analysis under such a situation,particularly when the details of collision are taken into consideration,are less known.In this paper,we provide a framework for analytically evaluating the actual detection performance in a random temporal multiple access system where nodes can only transmit.Explicit expressions are provided for collision probability and signal to interference and noise ratio(SINR)when different numbers of packets are collided.We then discuss and compare two receiver options for the AP,and provide detailed receiver design for the premium one.In particular,we propose a synchronization scheme which can largely reduce the preamble length.We also demonstrate that system performance could be a convex function of preamble length both analytically and via simulation,as well as the forward error correction(FEC)coding rate.
基金This work was supported by the National Natural Science Foundation of China(Nos.21722103,21931005,21720102002,and 21673140)Shanghai Science and Technology Committee(No.19JC1412600)the SJTU-MPI partner group.The authors thank Shanghai Synchrotron Radiation Facility for providing beam time(No.BL14W1).
文摘The rational design of highly active and stable atomically dispersed M-X4(M=Fe,Co,Ni,etc.,X=C,N)-based catalysts holds promises for wide application in almost all realms of catalysis.Despite great effort in the construction of specific M-X4 centers,the possible effect of non-coordinated heteroatoms on the catalytic activity of metal centers has been rarely explored.Herein,we develop a new type of M-X4 catalyst composed of Fe-N4 centers and non-coordinated B heteroatoms(FeNC+B)and find the key role of non-coordinated B adjacent to Fe-N4 centers in tailoring their electron density and final catalytic selectivity.The experimental and theoretical results demonstrated that non-coordinated boron atoms could decrease the electron density of Fe-N4 centers to a suitable level and thus boost the selective production of nitriles from amine oxidation by depressing the formation of imines due to the flattened energy barrier of the reversible conversion of imines back to amines.As a reusable heterocatalyst,the state-of-the-art FeNC+B catalyst provides a turn-over frequency(TOF)value of 21.6 molbenzonitrile·molFe^−1·h^−1(100℃),outpacing that of bench-marked nonnoble-metal-based homogeneous catalyst by a factor of 3.4.
基金Under the auspices of National Natural Science Foundation of China(No.41071109)Fundamental Research Funds for the Central University(No.10SSXT137)
文摘Urbanization is a comprehensive concept, a trinity process that population urbanization, economic urbanization and space urbanization, is based on the interactions and mutual influences among the in which, people are the central and leading players in this process, while economic activities serve as the driving force and space is the carrier-the physical or material setting as well as the product. So the coordination among these processes is crucial for a country or region＇s sustainable development. China is experiencing rapid growth of cities and a surge in urban population, with the basic national condition of many people and little land, which calls for a systematic study of the issue of coordinated urbanization from theoretical, methodological and practical perspectives. Based on the concept of urbanization and non-coordination of urbanization, this article built a quantitative method to identify and evaluate the urbanization and non-coordination of urbanization, and made an empirical analysis in China between 2000 and 2008. The results show that the non-coordination overall level of China＇s urbanization declined during the study period, because population urbanization, economic urbanization, and space urbanization exhibited different trajectories of change. This study also reveals that performance assessment system, household registration system, and urban land expropriation system, etc., are the main affecting factors. At the end, we put forward some suggestions to achieve sustainable development of China＇s urbanization from the aspects of improving the local government＇s obiective function, imolementing the urban plalming svstem, enforcing public particination asnects and so on.
基金financial support from the National Natural Science Foundation of China(Nos.21776111,21861039)the Fundamental Research Funds for the Central Universities(No.JUSRP 51627B)the Ministry of Education and the State Administration of Foreign Experts Affairs for the 111 Project(No.B13025)。
文摘Several novel pyridine-oxadiazole iridium complexes were synthesized and characterized through X-ray crystallography.The designed iridium.complexes revealed surprisingly high catalytic activity in C-N bondformation of amides and benzyl alcohols with the assistance of non-coordinating anions.In an attempt to achieve borrowing hydrogen reactions of amides with benzyl alcohols,N,N'-(phenylmethylene)dibenzamide products we re unexpectedly isolated under non-coordinating anion conditions,whereas N-benzylbenzamide products were achieved in the absence of non-coordinating anions.The mechanism explorations excluded the possibility of"silver effect"(silver-assisted or bimetallic catalysis)and revealed that the reactivity of iridium catalyst was varied by non-coordinating anions.This work provided a convenient and useful methodology that allowed the iridium complex to be a chemoselective catalyst and demonstrated the first example of non-coordinating-anion-tuned selective C-N bond formation.
