A series of self-reducing bifunctional Ni-W/SBA-15 catalysts were synthesized using biomass-based carbon source as the reducing agent without conventional further reduction step. The self-reducing catalysts were perfo...A series of self-reducing bifunctional Ni-W/SBA-15 catalysts were synthesized using biomass-based carbon source as the reducing agent without conventional further reduction step. The self-reducing catalysts were performed on the hydrogenolysis of cellulose to low carbon polyols. The effects of calcination temperature and metallic loading contents for cellulose hydrogenolysis reaction were investigated detailedly.The optimal calcination temperature was found to be 673 K by TG analysis. The active metal nanoparticles with a better dispersion were observed using SEM and element mapping technology. The yield of low carbon polyols using the catalyst with the receipt of 10%Ni-15%W/SBA-15-673 K can reach as high as68.14%, of which the ethylene glycol(EG) accounts for 61.04%.展开更多
The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-...The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-1,5-di-furanyl catalyzed by DBU reached 98.0% under optimized conditions. According to the kinetic analysis, the reaction order of furfural was estimated as 1.0, the apparent activation energy was 17.7 kJ.mol.1, and the pre-exponential factor was 2.67 L.min.1 in fitting with the Arrhenius equation, which explains the high efficiency of the DBU catalyst. DBU-catalyzed aldol condensation with free solvent offers an alternative route to simplify aldol condensation and separation into a single step.展开更多
Background:Telesurgery has the potential to overcome spatial limitations for surgeons,which depends on surgical robot and the quality of network communication.However,the influence of network latency and bandwidth on ...Background:Telesurgery has the potential to overcome spatial limitations for surgeons,which depends on surgical robot and the quality of network communication.However,the influence of network latency and bandwidth on telesurgery is not well understood.Methods:A telesurgery system capable of dynamically adjusting image compression ratios in response to bandwidth changes was established between Beijing and Sanya(Hainan province),covering a distance of 3000 km.In total,108 animal operations,including 12 surgical procedures,were performed.Total latency ranging from 170 ms to 320 ms and bandwidth from 15-20 Mbps to less than 1 Mbps were explored using designed surgical tasks and hemostasis models for renal vein and internal iliac artery rupture bleeding.Network latency,jitter,frame loss,and bit rate code were systemically measured during these operations.National Aeronautics and Space Administration Task Load Index(NASA-TLX)and a self-designed scale measured the workload and subjective perception of surgeons.Results:All 108 animal telesurgeries,conducted from January 2023 to June 2023,were performed effectively over a total duration of 3866 min.The operations were completed with latency up to 320 ms and bandwidths as low as 1-5 Mbps.Hemostasis for vein and artery rupture bleeding models was effectively achieved under these low bandwidth conditions.The NASA-TLX results indicated that latency significantly impacted surgical performance more than bandwidth and image clarity reductions.Conclusions:This telesurgery system demonstrated safety and reliability.A total of 320 ms latency is acceptable for telesurgery operations.Reducing image clarity can effectively mitigate the potential latency increase caused by decreased bandwidth,offering a new method to reduce the impact of latency on telesurgery.展开更多
Satellite communications and reconfigurable intelligent surface (RIS) are considered as twopromising technologies that can significantly improve the coverage and energy efficiency of futurewireless communication netwo...Satellite communications and reconfigurable intelligent surface (RIS) are considered as twopromising technologies that can significantly improve the coverage and energy efficiency of futurewireless communication networks. The satellite communications security is often threatened dueto its broadcasting nature. To enhance the physical layer security (PLS) of satellite communications with channel similarity, an aerial RIS-aided dual full-duplex (DFD-ARIS) cooperative jamming method is presented in this paper. Specifically, unlike the existing works that relied onchannel difference, DFD-ARIS utilizes the channel similarity against the eavesdroppers with thehelp of ARIS. In addition, the power allocation is further studied in conjunction with the phasedesign of RIS to minimize the total power under the constraints of data rate, satellite powerlimitation and secrecy rate. Then, the closed-form solutions are achieved. Simulation results showthat the performance of the proposed scheme is superior to the traditional method.展开更多
The amplify-and-forward(AF)relay is widely employed owing to its simplicity,while reconfig-urable intelligent surface(RIS)technology is envisioned as the next generation of relay technology due to its high energy effi...The amplify-and-forward(AF)relay is widely employed owing to its simplicity,while reconfig-urable intelligent surface(RIS)technology is envisioned as the next generation of relay technology due to its high energy efficiency.This paper compares these two technologies at the physical layer security(PLS)level for non-orthogonal multiple access(NOMA)with an internal near-end eavesdropper.Specifically,for a fair comparison,both the number of RIS elements and AF relay antennas are set to N,and similar secure transport strategies are utilized for both models to maximize the secrecy rate.Analytical results demonstrate that the PLS performance of RIS-assisted NOMA is better than that of AF relay-assisted NOMA if N reaches a certain threshold.Simulation results verify the correctness of the theoretical analysis.展开更多
基金supported by scientific research project of Zhejiang Provincial Education Department(Grant No.Y20112088,China)Science and technology project of Zhejiang Province(Grant No.2011R09028-10,China)
文摘A series of self-reducing bifunctional Ni-W/SBA-15 catalysts were synthesized using biomass-based carbon source as the reducing agent without conventional further reduction step. The self-reducing catalysts were performed on the hydrogenolysis of cellulose to low carbon polyols. The effects of calcination temperature and metallic loading contents for cellulose hydrogenolysis reaction were investigated detailedly.The optimal calcination temperature was found to be 673 K by TG analysis. The active metal nanoparticles with a better dispersion were observed using SEM and element mapping technology. The yield of low carbon polyols using the catalyst with the receipt of 10%Ni-15%W/SBA-15-673 K can reach as high as68.14%, of which the ethylene glycol(EG) accounts for 61.04%.
文摘The kinetics of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-catalyzed aldol condensation of furfural with acetone was investigated under free solvent conditions from 50℃ - 90℃. The highest yield of 1,4-pentandien-3-on-1,5-di-furanyl catalyzed by DBU reached 98.0% under optimized conditions. According to the kinetic analysis, the reaction order of furfural was estimated as 1.0, the apparent activation energy was 17.7 kJ.mol.1, and the pre-exponential factor was 2.67 L.min.1 in fitting with the Arrhenius equation, which explains the high efficiency of the DBU catalyst. DBU-catalyzed aldol condensation with free solvent offers an alternative route to simplify aldol condensation and separation into a single step.
基金National Natural Science Foundation of China(No.M-0735)
文摘Background:Telesurgery has the potential to overcome spatial limitations for surgeons,which depends on surgical robot and the quality of network communication.However,the influence of network latency and bandwidth on telesurgery is not well understood.Methods:A telesurgery system capable of dynamically adjusting image compression ratios in response to bandwidth changes was established between Beijing and Sanya(Hainan province),covering a distance of 3000 km.In total,108 animal operations,including 12 surgical procedures,were performed.Total latency ranging from 170 ms to 320 ms and bandwidth from 15-20 Mbps to less than 1 Mbps were explored using designed surgical tasks and hemostasis models for renal vein and internal iliac artery rupture bleeding.Network latency,jitter,frame loss,and bit rate code were systemically measured during these operations.National Aeronautics and Space Administration Task Load Index(NASA-TLX)and a self-designed scale measured the workload and subjective perception of surgeons.Results:All 108 animal telesurgeries,conducted from January 2023 to June 2023,were performed effectively over a total duration of 3866 min.The operations were completed with latency up to 320 ms and bandwidths as low as 1-5 Mbps.Hemostasis for vein and artery rupture bleeding models was effectively achieved under these low bandwidth conditions.The NASA-TLX results indicated that latency significantly impacted surgical performance more than bandwidth and image clarity reductions.Conclusions:This telesurgery system demonstrated safety and reliability.A total of 320 ms latency is acceptable for telesurgery operations.Reducing image clarity can effectively mitigate the potential latency increase caused by decreased bandwidth,offering a new method to reduce the impact of latency on telesurgery.
基金supported in part by the National Natural Science Foundation of China(62171354)the key R&D plan of Shaanxi Province(2019ZDLGY07-02)+1 种基金the Fundamental Research Funds for the Central Universities,the National Natural Science Foundation of China(61501347)the“111”project(B08038).
文摘Satellite communications and reconfigurable intelligent surface (RIS) are considered as twopromising technologies that can significantly improve the coverage and energy efficiency of futurewireless communication networks. The satellite communications security is often threatened dueto its broadcasting nature. To enhance the physical layer security (PLS) of satellite communications with channel similarity, an aerial RIS-aided dual full-duplex (DFD-ARIS) cooperative jamming method is presented in this paper. Specifically, unlike the existing works that relied onchannel difference, DFD-ARIS utilizes the channel similarity against the eavesdroppers with thehelp of ARIS. In addition, the power allocation is further studied in conjunction with the phasedesign of RIS to minimize the total power under the constraints of data rate, satellite powerlimitation and secrecy rate. Then, the closed-form solutions are achieved. Simulation results showthat the performance of the proposed scheme is superior to the traditional method.
基金supported by the Fundamental Research Funds for the Central Universities,the Innovation Fund of Xidian University,the China National Key R&D Program(2021YFA1000500 and 2023YFB2904804)National Natural Science Foundation of China(62331023,62101492,62394292 and U20A20158)the Youth Innovation Team of Shaanxi Universities,the Double First-Class Overseas Research Scholarship Fund of Xidian University。
文摘The amplify-and-forward(AF)relay is widely employed owing to its simplicity,while reconfig-urable intelligent surface(RIS)technology is envisioned as the next generation of relay technology due to its high energy efficiency.This paper compares these two technologies at the physical layer security(PLS)level for non-orthogonal multiple access(NOMA)with an internal near-end eavesdropper.Specifically,for a fair comparison,both the number of RIS elements and AF relay antennas are set to N,and similar secure transport strategies are utilized for both models to maximize the secrecy rate.Analytical results demonstrate that the PLS performance of RIS-assisted NOMA is better than that of AF relay-assisted NOMA if N reaches a certain threshold.Simulation results verify the correctness of the theoretical analysis.
