以三聚氰胺苯甲酸盐为碳源和氮源、以三聚氰胺磷钼酸盐为钼源、磷源和氮源,采用程序升温的方法制备了系列N,P掺杂型C@Mo_(2)C催化剂。采用XRD、SEM、TEM和XPS等对催化剂的结构、形貌和表面特性进行了表征,研究了三聚氰胺苯甲酸盐中n(三...以三聚氰胺苯甲酸盐为碳源和氮源、以三聚氰胺磷钼酸盐为钼源、磷源和氮源,采用程序升温的方法制备了系列N,P掺杂型C@Mo_(2)C催化剂。采用XRD、SEM、TEM和XPS等对催化剂的结构、形貌和表面特性进行了表征,研究了三聚氰胺苯甲酸盐中n(三聚氰胺)/n(苯甲酸)、前驱体中n(C)/n(Mo)等因素对所制备催化剂的结构及其在二氧化碳加氢反应中催化性能的影响。在反应温度为220℃、反应压力为3.0 MPa、空速为3600 m L/(g·h)的条件下,在N,P掺杂型C@Mo_(2)C的催化作用下,CO_(2)转化率可以达到12.2%,此时产物中CH_(3)OH的选择性达到52.2%。展开更多
Denote by E(X,Y)the nuber of integers n∈[X,X+Y] which is not the sum of a prime and a square.In this paper we prove that E(X,Y)《Y(logX)^-A for any A>0 provided that Y》X^7/12+s.
Hydrogen evolution reaction is a critical reaction in water splitting for hydrogen production.However,developing effective and stable non‐noble‐metal electrocatalysts which work well at high current densities demand...Hydrogen evolution reaction is a critical reaction in water splitting for hydrogen production.However,developing effective and stable non‐noble‐metal electrocatalysts which work well at high current densities demanded by industry still remain great challenge.Herein,taking advantage of the highly tunable metal‐organic framework(MOF)templates,nitrogen doped binary transition metal phosphides electrocatalysts(N‐CoP_(x)/Ni_(2)P)with three‐dimensional(3D)conductive network structure were successfully synthesized.The 3D open porous channels could expose more catalytically active sites;nitrogen doping and the synergistic effect between CoP and Ni_(2)P can increase the electron density of Co atoms at active sites,further optimizing the Gibbs free energy of hydrogen(ΔGH*)and water(ΔG_(H_(2)O*)).As a result,the obtained N‐CoP_(x)/Ni_(2)P catalyst exhibits extraordinary electrocatalytic activity in a wide pH range.Especially,it requires an extremely low overpotential of 152 mV to deliver a high current density of 650 mA cm^(–2) in alkaline media.This work may shed some light on the rational design of cheap electrocatalysts and electrode materials that work well at high current densities.展开更多
A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-1-ferrocenylethylamine. In a model reaction of Pd-catalyzed allylic alkylation of 1,3-d...A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-1-ferrocenylethylamine. In a model reaction of Pd-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate 6 with dimethyl malonate, good enantioselectivity (86% e.e.) was obtained.展开更多
This paper proposes a new discrete-time Geo/G/1 queueing model under the control of bi-level randomized(p,N1,N2)-policy.That is,the server is closed down immediately when the system is empty.If N1(≥1)customers are ac...This paper proposes a new discrete-time Geo/G/1 queueing model under the control of bi-level randomized(p,N1,N2)-policy.That is,the server is closed down immediately when the system is empty.If N1(≥1)customers are accumulated in the queue,the server is activated for service with probability p(0≤p≤1)or still left off with probability(1−p).When the number of customers in the system becomes N_(2)(≥N1),the server begins serving the waiting customers until the system becomes empty again.For the model,firstly,we obtain the transient solution of the queue size distribution and the explicit recursive formulas of the stationary queue length distribution by employing the total probability decomposition technique.Then,the expressions of its probability generating function of the steady-state queue size and the expected steady-state queue size are presented.Additionally,numerical examples are conducted to discuss the effect of the system parameters on some performance indices.Furthermore,the steady-state distribution of queue length at epochs n−,n and outside observer’s observation epoch are explored,respectively.Finally,we establish a cost function to investigate the cost optimization problem under the constraint of the average waiting time.And the presented model provides a less expected cost as compared to the traditional N-policy.展开更多
文摘以三聚氰胺苯甲酸盐为碳源和氮源、以三聚氰胺磷钼酸盐为钼源、磷源和氮源,采用程序升温的方法制备了系列N,P掺杂型C@Mo_(2)C催化剂。采用XRD、SEM、TEM和XPS等对催化剂的结构、形貌和表面特性进行了表征,研究了三聚氰胺苯甲酸盐中n(三聚氰胺)/n(苯甲酸)、前驱体中n(C)/n(Mo)等因素对所制备催化剂的结构及其在二氧化碳加氢反应中催化性能的影响。在反应温度为220℃、反应压力为3.0 MPa、空速为3600 m L/(g·h)的条件下,在N,P掺杂型C@Mo_(2)C的催化作用下,CO_(2)转化率可以达到12.2%,此时产物中CH_(3)OH的选择性达到52.2%。
文摘Denote by E(X,Y)the nuber of integers n∈[X,X+Y] which is not the sum of a prime and a square.In this paper we prove that E(X,Y)《Y(logX)^-A for any A>0 provided that Y》X^7/12+s.
文摘Hydrogen evolution reaction is a critical reaction in water splitting for hydrogen production.However,developing effective and stable non‐noble‐metal electrocatalysts which work well at high current densities demanded by industry still remain great challenge.Herein,taking advantage of the highly tunable metal‐organic framework(MOF)templates,nitrogen doped binary transition metal phosphides electrocatalysts(N‐CoP_(x)/Ni_(2)P)with three‐dimensional(3D)conductive network structure were successfully synthesized.The 3D open porous channels could expose more catalytically active sites;nitrogen doping and the synergistic effect between CoP and Ni_(2)P can increase the electron density of Co atoms at active sites,further optimizing the Gibbs free energy of hydrogen(ΔGH*)and water(ΔG_(H_(2)O*)).As a result,the obtained N‐CoP_(x)/Ni_(2)P catalyst exhibits extraordinary electrocatalytic activity in a wide pH range.Especially,it requires an extremely low overpotential of 152 mV to deliver a high current density of 650 mA cm^(–2) in alkaline media.This work may shed some light on the rational design of cheap electrocatalysts and electrode materials that work well at high current densities.
基金supported by the National Natural Science Foundation of China(29933050)
文摘A novel chiral bis(ferrocenyl) P2N ligand 1 with C2-symmetry was synthesized through a four-step procedure from (R)-N,N-dimethyl-1-ferrocenylethylamine. In a model reaction of Pd-catalyzed allylic alkylation of 1,3-diphenylprop-2-enyl acetate 6 with dimethyl malonate, good enantioselectivity (86% e.e.) was obtained.
基金Supported by the National Natural Science Foundation of China(71571127)the Opening Fund of Key Laboratory of Higher Education of Sichuan Province for Enterprise Informationalization and Internet of Things(2023WZJ02)。
文摘This paper proposes a new discrete-time Geo/G/1 queueing model under the control of bi-level randomized(p,N1,N2)-policy.That is,the server is closed down immediately when the system is empty.If N1(≥1)customers are accumulated in the queue,the server is activated for service with probability p(0≤p≤1)or still left off with probability(1−p).When the number of customers in the system becomes N_(2)(≥N1),the server begins serving the waiting customers until the system becomes empty again.For the model,firstly,we obtain the transient solution of the queue size distribution and the explicit recursive formulas of the stationary queue length distribution by employing the total probability decomposition technique.Then,the expressions of its probability generating function of the steady-state queue size and the expected steady-state queue size are presented.Additionally,numerical examples are conducted to discuss the effect of the system parameters on some performance indices.Furthermore,the steady-state distribution of queue length at epochs n−,n and outside observer’s observation epoch are explored,respectively.Finally,we establish a cost function to investigate the cost optimization problem under the constraint of the average waiting time.And the presented model provides a less expected cost as compared to the traditional N-policy.
