The nozzle inner-flow characteristic of the“spray G”injector was studied by the computational fluid dynamics(CFD)simulation,and the sensitivity of cycle fuel mass to the conicity and entrance radius of the nozzle ho...The nozzle inner-flow characteristic of the“spray G”injector was studied by the computational fluid dynamics(CFD)simulation,and the sensitivity of cycle fuel mass to the conicity and entrance radius of the nozzle hole were analyzed.Results show that the inner conicity of nozzle hole inhibits the development of cavitation phenomena,and increases the injection rate.While the outer conicity of nozzle hole promotes the diffusion of cavita-tion,leading to reductions of the liquid volume fraction of the nozzle outlet and the local flow resistance of the nozzle hole.The sensitivity of cycle fuel mass to inner-cone nozzle hole is stronger than that of the outer-cone noz-zle,especially at the smaller hole conicity.The increase of injection pressure enhances the sensitivity of the injection characteristics to the nozzle hole structure,in which inner-cone nozzle has higher sensitivity coefficient than the outer-cone nozzle hole.However,the increase of injection pressure aggravates the offset of liquid jet to the nozzle axis of the outer-cone nozzle hole.With the increase of the inner conicity of nozzle,the sensitivity of the injection characteristics to the entrance radius of the hole decreases.With the increase of the outer conicity of nozzle hole,the sensitivity of the injection characteristics to the entrance radius of the hole increases.展开更多
Heat and mass transfer of a circular-shaped porous moist object inside a two-dimensional triangle cavity is investigated by using finite element method.The porous object is considered to be a moist food sample,located...Heat and mass transfer of a circular-shaped porous moist object inside a two-dimensional triangle cavity is investigated by using finite element method.The porous object is considered to be a moist food sample,located in the middle of the cavity with inlet and outlet ports with different configurations of inlet/outlet ports.Convective drying performance is numerically assessed for different values of Reynolds numbers(between 50 and 250),dry air inlet temperature(between 40 and 80℃)and different locations of the port.It is observed that changing the port locations has significant impacts on the flow recirculaitons inside the triangular chamber while convective drying performance is highly affected.The moisture content reduces with longer time and for higher Reynolds number(Re)values.Case P4 where inlet and outlet ports are in the middle of the walls provides the most effective configuration in terms of convective drying performance while the worst case is seen for P1 case where inlet and outlet are closer to the corners of the chamber.There is a 192% difference between the moisture reduction of these two cases at Re=250,T=80℃ and t=120 min.展开更多
Since the first description of the concept of natural orifice translumenal endoscopic surgery (NOTES), a substantial number of clinical NOTES reports have appeared in the literature. This editorial reviews the availab...Since the first description of the concept of natural orifice translumenal endoscopic surgery (NOTES), a substantial number of clinical NOTES reports have appeared in the literature. This editorial reviews the available human data addressing research questions originally proposed by the white paper, including determining the optimal method of access for NOTES, developing safe methods of lumenal closure, suturing and anastomotic devices, advanced multitasking platforms, addressing the risk of infection, managing complications, addressing challenges with visualization, and training for NOTES procedures. An analysis of the literature reveals that so far transvaginal access and closure appear to be the most feasible techniques for NOTES, with a limited, but growing transgastric, transrectal, and transesophageal NOTES experience in humans. The theoretically increased risk of infection as a result of NOTES procedures has not been substantiated in transvaginal and transgastric procedures so far. Development of suturing and anastomotic devices and advanced platforms for NOTES has progressed slowly, with limited clinical data on their use so far. Data onthe optimal management and incidence of intraoperative complications remain sparse, although possible factors contributing to complications are discussed. Finally, this editorial discusses the likely direction of future NOTES development and its possible role in clinical practice.展开更多
Recent studies confirm that the emerging bifunctional catalysts consisting of metal oxide and zeolites can directly convert syngas into high-quality gasoline,however,the formation mechanism of iso-paraffins and the di...Recent studies confirm that the emerging bifunctional catalysts consisting of metal oxide and zeolites can directly convert syngas into high-quality gasoline,however,the formation mechanism of iso-paraffins and the difference with the conventional FT/zeolite catalyst have not been investigated.Herein,three one-dimensional SAPO zeolites with diverse micropore sizes were synthesized and assembled with ZnAlO_(x)with spinel structure.It was found that ZnAlO_(x)/SAPO-41 and ZnAlO_(x)/SAPO-11 with medium micropore sizes favored the formation of C_(5)–C_(11)hydrocarbons with a high content of iso-paraffins.The characterizations pointed out that the formation of iso-paraffins over SAPO-11 followed a pore-mouth catalysis mechanism,which means the isomerization of linear hydrocarbons can only take place near the pore mouth region of zeolites.This mechanism only allows the formation of mono-branched iso-paraffins in the C_(5)–C_(11)range,which are less prone to be cracked than their di-branched isomers.A careful comparative analysis between ZnAlO_(x)/SAPO-11 and Co/H-meso-ZSM-5 was also made in terms of product distribution,activity,and stability.展开更多
Stabilizing gold nanoparticles（AuNPs） within a desired size range is critical to realize their promising catalytic performance in many important reactions.Herein,we investigate the anti-sintering properties of cubic...Stabilizing gold nanoparticles（AuNPs） within a desired size range is critical to realize their promising catalytic performance in many important reactions.Herein,we investigate the anti-sintering properties of cubic mesoporous silica（FDU-12） as a function of pore entrance size.Simple adjustments to the type of organic template and reaction temperature enable the successful synthesis of FDU-12 with controllable entrance sizes（ 3,3-5 and 7 nm）.Excellent anti-sintering properties are observed for FDU-12 with a sub-5-nm entrance size（3-5 nm） over a wide loading concentration（1.0-8.3 wt%） and the AuNPs can be stabilized within a 4.5-5.0-nm range after calcination at 550 ℃in air for 5 h.Smaller entrance size（ 3 nm） prevents ingress of 3-nm AuNPs to the mesopores and results in low loading capacity and sintering.Conversely,FDU-12 possessing a larger entrance size（7 nm） shows promising anti-sintering properties at high loading concentrations,although catalytic performance is significantly lost at lower concentrations（e.g.2.1 wt%,14.2 ± 5.5 nm）.Different anti-sintering mechanisms are proposed for each of the different FDU-12 entrance sizes.Additionally,catalytic data indicates that the obtained 4.5-nm AuNPs supported on FDU-12 with a sub-5-nm entrance size exhibit excellent mass-specific activity（1544 mmol g_（Au）^（-1） h^（-1）） and selectivity（ 99%）at 230 ℃ for the gas-phase selective oxidation of cyclohexanol.展开更多
文摘The nozzle inner-flow characteristic of the“spray G”injector was studied by the computational fluid dynamics(CFD)simulation,and the sensitivity of cycle fuel mass to the conicity and entrance radius of the nozzle hole were analyzed.Results show that the inner conicity of nozzle hole inhibits the development of cavitation phenomena,and increases the injection rate.While the outer conicity of nozzle hole promotes the diffusion of cavita-tion,leading to reductions of the liquid volume fraction of the nozzle outlet and the local flow resistance of the nozzle hole.The sensitivity of cycle fuel mass to inner-cone nozzle hole is stronger than that of the outer-cone noz-zle,especially at the smaller hole conicity.The increase of injection pressure enhances the sensitivity of the injection characteristics to the nozzle hole structure,in which inner-cone nozzle has higher sensitivity coefficient than the outer-cone nozzle hole.However,the increase of injection pressure aggravates the offset of liquid jet to the nozzle axis of the outer-cone nozzle hole.With the increase of the inner conicity of nozzle,the sensitivity of the injection characteristics to the entrance radius of the hole decreases.With the increase of the outer conicity of nozzle hole,the sensitivity of the injection characteristics to the entrance radius of the hole increases.
文摘Heat and mass transfer of a circular-shaped porous moist object inside a two-dimensional triangle cavity is investigated by using finite element method.The porous object is considered to be a moist food sample,located in the middle of the cavity with inlet and outlet ports with different configurations of inlet/outlet ports.Convective drying performance is numerically assessed for different values of Reynolds numbers(between 50 and 250),dry air inlet temperature(between 40 and 80℃)and different locations of the port.It is observed that changing the port locations has significant impacts on the flow recirculaitons inside the triangular chamber while convective drying performance is highly affected.The moisture content reduces with longer time and for higher Reynolds number(Re)values.Case P4 where inlet and outlet ports are in the middle of the walls provides the most effective configuration in terms of convective drying performance while the worst case is seen for P1 case where inlet and outlet are closer to the corners of the chamber.There is a 192% difference between the moisture reduction of these two cases at Re=250,T=80℃ and t=120 min.
文摘Since the first description of the concept of natural orifice translumenal endoscopic surgery (NOTES), a substantial number of clinical NOTES reports have appeared in the literature. This editorial reviews the available human data addressing research questions originally proposed by the white paper, including determining the optimal method of access for NOTES, developing safe methods of lumenal closure, suturing and anastomotic devices, advanced multitasking platforms, addressing the risk of infection, managing complications, addressing challenges with visualization, and training for NOTES procedures. An analysis of the literature reveals that so far transvaginal access and closure appear to be the most feasible techniques for NOTES, with a limited, but growing transgastric, transrectal, and transesophageal NOTES experience in humans. The theoretically increased risk of infection as a result of NOTES procedures has not been substantiated in transvaginal and transgastric procedures so far. Development of suturing and anastomotic devices and advanced platforms for NOTES has progressed slowly, with limited clinical data on their use so far. Data onthe optimal management and incidence of intraoperative complications remain sparse, although possible factors contributing to complications are discussed. Finally, this editorial discusses the likely direction of future NOTES development and its possible role in clinical practice.
文摘Recent studies confirm that the emerging bifunctional catalysts consisting of metal oxide and zeolites can directly convert syngas into high-quality gasoline,however,the formation mechanism of iso-paraffins and the difference with the conventional FT/zeolite catalyst have not been investigated.Herein,three one-dimensional SAPO zeolites with diverse micropore sizes were synthesized and assembled with ZnAlO_(x)with spinel structure.It was found that ZnAlO_(x)/SAPO-41 and ZnAlO_(x)/SAPO-11 with medium micropore sizes favored the formation of C_(5)–C_(11)hydrocarbons with a high content of iso-paraffins.The characterizations pointed out that the formation of iso-paraffins over SAPO-11 followed a pore-mouth catalysis mechanism,which means the isomerization of linear hydrocarbons can only take place near the pore mouth region of zeolites.This mechanism only allows the formation of mono-branched iso-paraffins in the C_(5)–C_(11)range,which are less prone to be cracked than their di-branched isomers.A careful comparative analysis between ZnAlO_(x)/SAPO-11 and Co/H-meso-ZSM-5 was also made in terms of product distribution,activity,and stability.
基金supported by the National Natural Science Foundation of China(21222307,21373181,21403197,91545113,21503189)the Fundamental Research Funds for the Central Universities(2014XZZX003-02)+1 种基金Zhejiang Provincial Natural Science Foundation(LY15B030009)China Postdoctoral Science Foundation(2014M550333,2015T80636)~~
文摘Stabilizing gold nanoparticles（AuNPs） within a desired size range is critical to realize their promising catalytic performance in many important reactions.Herein,we investigate the anti-sintering properties of cubic mesoporous silica（FDU-12） as a function of pore entrance size.Simple adjustments to the type of organic template and reaction temperature enable the successful synthesis of FDU-12 with controllable entrance sizes（ 3,3-5 and 7 nm）.Excellent anti-sintering properties are observed for FDU-12 with a sub-5-nm entrance size（3-5 nm） over a wide loading concentration（1.0-8.3 wt%） and the AuNPs can be stabilized within a 4.5-5.0-nm range after calcination at 550 ℃in air for 5 h.Smaller entrance size（ 3 nm） prevents ingress of 3-nm AuNPs to the mesopores and results in low loading capacity and sintering.Conversely,FDU-12 possessing a larger entrance size（7 nm） shows promising anti-sintering properties at high loading concentrations,although catalytic performance is significantly lost at lower concentrations（e.g.2.1 wt%,14.2 ± 5.5 nm）.Different anti-sintering mechanisms are proposed for each of the different FDU-12 entrance sizes.Additionally,catalytic data indicates that the obtained 4.5-nm AuNPs supported on FDU-12 with a sub-5-nm entrance size exhibit excellent mass-specific activity（1544 mmol g_（Au）^（-1） h^（-1）） and selectivity（ 99%）at 230 ℃ for the gas-phase selective oxidation of cyclohexanol.
