Fluidized-bed reactor is a candidate for dimethyl ether (DME) synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol...Fluidized-bed reactor is a candidate for dimethyl ether (DME) synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller (BET), X-ray powder diffraction (XRD) and temperature programmed reduction (TPR).展开更多
In the littlest Higgs model with T-parity(LHT) the mirror quarks induce the special flavor structures and some new flavor-changing couplings,which could greatly enhance the production rates of the flavor-changing proc...In the littlest Higgs model with T-parity(LHT) the mirror quarks induce the special flavor structures and some new flavor-changing couplings,which could greatly enhance the production rates of the flavor-changing processes. We in this paper study some bottom and anti-strange production processes in the LHT model at the International Linear Collider(ILC),i.e.,e^+e^-→bs andγγ→bs.The results show that the production rates of these processes are sizeable for the favorable values of the parameters.Therefore,it is quite possible to test the LHT model or make some constraints on the relevant parameters of the LHT through the detection of these processes at the ILC.展开更多
This paper introduces the design of the TZ-2 high voltage modulator for electron cyclotron resonance heating (ECRH) on HL-2A tokamak. The high voltage power supplies (HVPS) for the cyclotron have to operate advant...This paper introduces the design of the TZ-2 high voltage modulator for electron cyclotron resonance heating (ECRH) on HL-2A tokamak. The high voltage power supplies (HVPS) for the cyclotron have to operate advantageously and flexibly, with high stabilization and good insulation to high-voltage. Moreover, the HVPS must carry out the function of protection quickly, for insure the security of people and devices in the experiment on HL-2A. In this year, the HVPS with these modulators satisfies the requirement of the experiment of HL-2A.展开更多
In this paper a comprehensive review of heat transfer enhancement through microchannels has been presented. Over the past few years due to multifunetion, shrinking package size and high power dissipation, the heat flu...In this paper a comprehensive review of heat transfer enhancement through microchannels has been presented. Over the past few years due to multifunetion, shrinking package size and high power dissipation, the heat flux per unit area has increased significantly. Microchannels, with their large heat transfer surface to volume ratio and their small volumes, have shown a good thermal performance. Microchannels have been proven to be a high per- formaace cooling technique which is able to dissipate heat flux effectively from localized hot spots over small surface area. A good amount of heat transfer augmentation techniques have been reported on flow disruption through microchannel. These techniques promote free stream separation at the leading edge which results in boundary layer development and enhanced mixing leading to increased heat transfer. Flow disruption can be achieved through passive surface modifications, such as, shape of channel, dimple surfaces, ribs, cavities, groove structures, porous medium, etc. Combined effects of these geometrical configurations in heat transfer augmenta- tion are also reported in the literature. In this paper recent developments in experimental and numerical simula- tions of single-phase liquid cooled microchannel have been discussed to analyze the pressure drop, friction and heat transfer characteristics due to different flow conditions, roughness structure and passive surface modifica- tions. It has been observed that the flow disruption techniques are effective for heat transfer enhancement with lower penalties of increased pressure drop. The review concludes with suggestions for future research in this area.展开更多
We present a novel electrochemical technique for the fabrication of nano-photonic crystal structures. Based on a specially designed electrolyte, porous silicon(PSi) layers with different porosities are possible to be ...We present a novel electrochemical technique for the fabrication of nano-photonic crystal structures. Based on a specially designed electrolyte, porous silicon(PSi) layers with different porosities are possible to be produced on highly-doped n-type silicon substrate by varying the applied current density which determines the size and the morphology of pores. By applying an alternative current density modulation during anodization, porous silicon photonic crystals are obtained using HF-containing electrolyte without oxidizing components. The current burst model(CBM) is employed to interpret the mechanism of the formation of the macropore porous silicon.展开更多
文摘Fluidized-bed reactor is a candidate for dimethyl ether (DME) synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller (BET), X-ray powder diffraction (XRD) and temperature programmed reduction (TPR).
基金Supported by the National Natural Science Foundation of China under Grant Nos.10775039,11075045by Specialized Research Fund for the Doctoral Program of Higher Education under Grant Nos.20094104110001,20104104110001by the Programme for Youth's Talents of Xinyang Normal University under Grant No.200950
文摘In the littlest Higgs model with T-parity(LHT) the mirror quarks induce the special flavor structures and some new flavor-changing couplings,which could greatly enhance the production rates of the flavor-changing processes. We in this paper study some bottom and anti-strange production processes in the LHT model at the International Linear Collider(ILC),i.e.,e^+e^-→bs andγγ→bs.The results show that the production rates of these processes are sizeable for the favorable values of the parameters.Therefore,it is quite possible to test the LHT model or make some constraints on the relevant parameters of the LHT through the detection of these processes at the ILC.
文摘This paper introduces the design of the TZ-2 high voltage modulator for electron cyclotron resonance heating (ECRH) on HL-2A tokamak. The high voltage power supplies (HVPS) for the cyclotron have to operate advantageously and flexibly, with high stabilization and good insulation to high-voltage. Moreover, the HVPS must carry out the function of protection quickly, for insure the security of people and devices in the experiment on HL-2A. In this year, the HVPS with these modulators satisfies the requirement of the experiment of HL-2A.
文摘In this paper a comprehensive review of heat transfer enhancement through microchannels has been presented. Over the past few years due to multifunetion, shrinking package size and high power dissipation, the heat flux per unit area has increased significantly. Microchannels, with their large heat transfer surface to volume ratio and their small volumes, have shown a good thermal performance. Microchannels have been proven to be a high per- formaace cooling technique which is able to dissipate heat flux effectively from localized hot spots over small surface area. A good amount of heat transfer augmentation techniques have been reported on flow disruption through microchannel. These techniques promote free stream separation at the leading edge which results in boundary layer development and enhanced mixing leading to increased heat transfer. Flow disruption can be achieved through passive surface modifications, such as, shape of channel, dimple surfaces, ribs, cavities, groove structures, porous medium, etc. Combined effects of these geometrical configurations in heat transfer augmenta- tion are also reported in the literature. In this paper recent developments in experimental and numerical simula- tions of single-phase liquid cooled microchannel have been discussed to analyze the pressure drop, friction and heat transfer characteristics due to different flow conditions, roughness structure and passive surface modifica- tions. It has been observed that the flow disruption techniques are effective for heat transfer enhancement with lower penalties of increased pressure drop. The review concludes with suggestions for future research in this area.
基金supported by the National Natural Science Foundation of China(No.61265009)the Excellent Youth Foundation of Shihezi University(No.2012ZRKXYQ-YD20)the Doctoral Research Foundation of Shihezi University(No.RCZX201327)
文摘We present a novel electrochemical technique for the fabrication of nano-photonic crystal structures. Based on a specially designed electrolyte, porous silicon(PSi) layers with different porosities are possible to be produced on highly-doped n-type silicon substrate by varying the applied current density which determines the size and the morphology of pores. By applying an alternative current density modulation during anodization, porous silicon photonic crystals are obtained using HF-containing electrolyte without oxidizing components. The current burst model(CBM) is employed to interpret the mechanism of the formation of the macropore porous silicon.