Distributed certification via threshold cryptography is much more secu re than other ways to protect certification authority (CA) 's private key,and c an tolerate some intrusions. As the original system such as IT...Distributed certification via threshold cryptography is much more secu re than other ways to protect certification authority (CA) 's private key,and c an tolerate some intrusions. As the original system such as ITTC,etc.,is unsaf e ,inefficient and impracitcal in actual network environment,this paper brings u p a new distributed certification scheme,which although it generates key shares concentratively,it updates key shares distributedly,and so,avoids single-po in t failure like ITTC. It not only enhances robustness with Feldman verification and SSL protocol,but can also change the threshold (t,k) flexibly and robu stly,and so,is much more practical. In this work,the authors implement the prototype sy stem of the new scheme and test and analyze its performance.展开更多
The widespread utilization of fossil fuels has caused an associated increase in CO_(2) emissions over the past few decades,which has resulted in global warming and ocean acidification.CO hydrogenation(Fischer‐Tropsch...The widespread utilization of fossil fuels has caused an associated increase in CO_(2) emissions over the past few decades,which has resulted in global warming and ocean acidification.CO hydrogenation(Fischer‐Tropsch synthesis,FTS)is considered a significant route for the production of liquid fuels and chemicals from nonpetroleum sources to meet worldwide demand.Conversion of CO_(2) with renewable H_(2) into valuable hydrocarbons is beneficial for reducing dependence on fossil fuels and mitigating the negative effects of high CO_(2) concentrations in the atmosphere.Iron‐based catalysts exhibit superior catalytic performance in both FTS and CO_(2) hydrogenation to value‐added hydrocarbons.The abundance and low cost of iron‐based catalysts also promote their wide application in CO_(x) hydrogenation.This paper provides a comprehensive overview of the significant developments in the application of iron‐based catalysts in these two fields.The active phases,promoter effect,and support of iron‐based catalysts are discussed in the present paper.Based on understanding of these three essential aspects,we also cover recent advances in the design and preparation of novel iron‐based catalysts for FTS and CO_(2) hydrogenation.Current challenges and future catalytic applications are also outlined.展开更多
Several high performance tokamak operation regimes have been achieved experimentally in the experiments with the peaked density profiles. The regimes include the improved Ohmic confinement in ASDEX, the pellet enhance...Several high performance tokamak operation regimes have been achieved experimentally in the experiments with the peaked density profiles. The regimes include the improved Ohmic confinement in ASDEX, the pellet enhanced performance mode in Alcator-C, and the super-shot mode in TFTR. In these regimes, peaked core density profiles are always existent, and almost always go with the internal transport barriers, these barriers generally produced by sheared radial electric field. In addition to enhance confinement, the peaked density profile is also needed for the optimized fusion reaction rate and alpha heating power in tokamak plasma, and combined peaked density profile and peaked temperature profile, would make the ignition condition easy obtained. It is desirable to seek and analyze the density profile control schemes that effectively lead to density profile peaking in particle transports experimental investigation.展开更多
The ECRH is an effective way of plasma heating on tokamak. The gyrotrons with two high voltage power supplies （ HVPS ） are used in ECRH experiment on the HL-2A tokamak. This type of gyrotron is benefit to improve th...The ECRH is an effective way of plasma heating on tokamak. The gyrotrons with two high voltage power supplies （ HVPS ） are used in ECRH experiment on the HL-2A tokamak. This type of gyrotron is benefit to improve the output efficiency and HVPS design. So the anode HVPS with higher output power, reliable characteristic and controlling easily are necessary for the work of gyrotron normally.展开更多
Electron cyclotron resonance heating and electron cyclotron current drive （ ECRH/ECCD ） have been developed significantly in recent years in many devices such as Tore Supra, JT-60U, Heliotron J. It has many advantag...Electron cyclotron resonance heating and electron cyclotron current drive （ ECRH/ECCD ） have been developed significantly in recent years in many devices such as Tore Supra, JT-60U, Heliotron J. It has many advantages over other means of heating and current drive. The EC power can be injected as narrow gaussian beams, giving rise to so highly localized power deposition as to make ECRH an ideal candidate for local MHD control.展开更多
On August 25,2015 the CFHL technology for hydroupgrading of syncrude obtained from low-temperature Fischer-Tropsch synthesis had been successfully applied on the first in China 1.0 Mt/a indirect coal liquefaction unit.
CoCu/TiO_2 catalysts promoted using alkali metals（Li, Na, K, Rb, and Cs） were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the ...CoCu/TiO_2 catalysts promoted using alkali metals（Li, Na, K, Rb, and Cs） were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the alkali metals on the physicochemical properties of the CoCu/TiO_2 catalysts and the catalytic performance for CO_2 hydrogenation to long-chain hydrocarbons（C_（5＋））were investigated in this work. According to the characterization of the catalysts based on X-ray photoelectron spectroscopy, X-ray diffraction, CO_2 temperature-programmed desorption（TPD）, and H_2-TPD, the introduction of alkali metals could increase the CO_2 adsorption and decrease the H_2 chemisorption, which could suppress the formation of CH_4, enhance the production of C_（5＋）, and decrease the hydrogenation activity. Among all the promoters, the Na-modified CoCu/TiO_2 catalyst provided the maximum C_（5＋） yield of 5.4%, with a CO_2 conversion of 18.4% and C_（5＋） selectivity of42.1%, because it showed the strongest basicity and a slight decrease in the amount of H_2 desorption;it also exhibited excellent catalytic stability of more than 200 h.展开更多
Let H（x） be the interpolation polynomial of degree n for function f, where the interpolation nodes a0, a1, …, an may be repeated, For the interpolation remainder and its
We study the time-decay properties of weighted norms of solutions to the Stokes equations and the Navier-Stokes equations in the half-space Rn+ (n 2). Three kinds of the weighted Lp-Lr estimates are established for th...We study the time-decay properties of weighted norms of solutions to the Stokes equations and the Navier-Stokes equations in the half-space Rn+ (n 2). Three kinds of the weighted Lp-Lr estimates are established for the Stokes semigroup generated by the Stokes operator in the half-space R+n (n 2). As an application of the weighted estimates of the Stokes semigroup, a class of local and global strong solutions in weighted Lp (R+n) are constructed, following the approach given by Kato.展开更多
文摘Distributed certification via threshold cryptography is much more secu re than other ways to protect certification authority (CA) 's private key,and c an tolerate some intrusions. As the original system such as ITTC,etc.,is unsaf e ,inefficient and impracitcal in actual network environment,this paper brings u p a new distributed certification scheme,which although it generates key shares concentratively,it updates key shares distributedly,and so,avoids single-po in t failure like ITTC. It not only enhances robustness with Feldman verification and SSL protocol,but can also change the threshold (t,k) flexibly and robu stly,and so,is much more practical. In this work,the authors implement the prototype sy stem of the new scheme and test and analyze its performance.
文摘The widespread utilization of fossil fuels has caused an associated increase in CO_(2) emissions over the past few decades,which has resulted in global warming and ocean acidification.CO hydrogenation(Fischer‐Tropsch synthesis,FTS)is considered a significant route for the production of liquid fuels and chemicals from nonpetroleum sources to meet worldwide demand.Conversion of CO_(2) with renewable H_(2) into valuable hydrocarbons is beneficial for reducing dependence on fossil fuels and mitigating the negative effects of high CO_(2) concentrations in the atmosphere.Iron‐based catalysts exhibit superior catalytic performance in both FTS and CO_(2) hydrogenation to value‐added hydrocarbons.The abundance and low cost of iron‐based catalysts also promote their wide application in CO_(x) hydrogenation.This paper provides a comprehensive overview of the significant developments in the application of iron‐based catalysts in these two fields.The active phases,promoter effect,and support of iron‐based catalysts are discussed in the present paper.Based on understanding of these three essential aspects,we also cover recent advances in the design and preparation of novel iron‐based catalysts for FTS and CO_(2) hydrogenation.Current challenges and future catalytic applications are also outlined.
文摘Several high performance tokamak operation regimes have been achieved experimentally in the experiments with the peaked density profiles. The regimes include the improved Ohmic confinement in ASDEX, the pellet enhanced performance mode in Alcator-C, and the super-shot mode in TFTR. In these regimes, peaked core density profiles are always existent, and almost always go with the internal transport barriers, these barriers generally produced by sheared radial electric field. In addition to enhance confinement, the peaked density profile is also needed for the optimized fusion reaction rate and alpha heating power in tokamak plasma, and combined peaked density profile and peaked temperature profile, would make the ignition condition easy obtained. It is desirable to seek and analyze the density profile control schemes that effectively lead to density profile peaking in particle transports experimental investigation.
文摘The ECRH is an effective way of plasma heating on tokamak. The gyrotrons with two high voltage power supplies （ HVPS ） are used in ECRH experiment on the HL-2A tokamak. This type of gyrotron is benefit to improve the output efficiency and HVPS design. So the anode HVPS with higher output power, reliable characteristic and controlling easily are necessary for the work of gyrotron normally.
文摘Electron cyclotron resonance heating and electron cyclotron current drive （ ECRH/ECCD ） have been developed significantly in recent years in many devices such as Tore Supra, JT-60U, Heliotron J. It has many advantages over other means of heating and current drive. The EC power can be injected as narrow gaussian beams, giving rise to so highly localized power deposition as to make ECRH an ideal candidate for local MHD control.
文摘On August 25,2015 the CFHL technology for hydroupgrading of syncrude obtained from low-temperature Fischer-Tropsch synthesis had been successfully applied on the first in China 1.0 Mt/a indirect coal liquefaction unit.
文摘CoCu/TiO_2 catalysts promoted using alkali metals（Li, Na, K, Rb, and Cs） were prepared by the homogeneous deposition-precipitation method followed by the incipient wetness impregnation method. The influences of the alkali metals on the physicochemical properties of the CoCu/TiO_2 catalysts and the catalytic performance for CO_2 hydrogenation to long-chain hydrocarbons（C_（5＋））were investigated in this work. According to the characterization of the catalysts based on X-ray photoelectron spectroscopy, X-ray diffraction, CO_2 temperature-programmed desorption（TPD）, and H_2-TPD, the introduction of alkali metals could increase the CO_2 adsorption and decrease the H_2 chemisorption, which could suppress the formation of CH_4, enhance the production of C_（5＋）, and decrease the hydrogenation activity. Among all the promoters, the Na-modified CoCu/TiO_2 catalyst provided the maximum C_（5＋） yield of 5.4%, with a CO_2 conversion of 18.4% and C_（5＋） selectivity of42.1%, because it showed the strongest basicity and a slight decrease in the amount of H_2 desorption;it also exhibited excellent catalytic stability of more than 200 h.
文摘Let H（x） be the interpolation polynomial of degree n for function f, where the interpolation nodes a0, a1, …, an may be repeated, For the interpolation remainder and its
基金supported in part by National Basic Research Program of China (Grant No. 2006CB805902)Knowledge Innovation Funds of Chinese Academy of Sciences(Grant No. KJCX3-SYW-S03)+1 种基金supported in part by Scientific Research Plan Projects of Shaanxi Education (Grant No. 09JK770)China Postdoctoral Science Foundation (Grant No. 20090461305)
文摘We study the time-decay properties of weighted norms of solutions to the Stokes equations and the Navier-Stokes equations in the half-space Rn+ (n 2). Three kinds of the weighted Lp-Lr estimates are established for the Stokes semigroup generated by the Stokes operator in the half-space R+n (n 2). As an application of the weighted estimates of the Stokes semigroup, a class of local and global strong solutions in weighted Lp (R+n) are constructed, following the approach given by Kato.
