In this study, two types of pre-distributors (nonuniform-pores and dual-baffle)for the combined solids-liquid distributor in gas-liquid-solid circulating fluidized bed heat exchanger, were designed and the characteris...In this study, two types of pre-distributors (nonuniform-pores and dual-baffle)for the combined solids-liquid distributor in gas-liquid-solid circulating fluidized bed heat exchanger, were designed and the characteristics of particles distribution was compared. In the experiments, the sampling method was used to measure local solids flux and a U shape pipe was used to measure static pressure drop in the lower pipe box.The effects of different superficial liquid velocities and liquid viscosities on the parameters mentioned above were investigated.The degree of distribution of local solids flux in exchanger pipe was evaluated by the non-uniformity function.The results showed that the two types of pre-distributors were both suitable for gas-liquid-solid circulating fluidized bed heat exchanger at a lower static pressure drop in the lower pipe box.Compared with the nonuniform-pores pre-distributor, the dual-baffle pre-distributor showed better performance.展开更多
Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is...Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is presented. The measurement of upward, downward and net solid fluxes was carried out in a cold model circulating fluidized bed (CFB) unit. The result shows that the profile of the net solid flux is in good agreement with the previous experimental data measured with a suction probe. The comparison between the average solid flux determined with the optical measuring system and the external solid flux was made, and the maximum deviationturned out to be 22%, with the average error being about 6.9%. These confirm that the optical fiber system can be successfully used to measure the upward, downward and net solid fluxes simultaneously by correctly processing the sampling signals obtained from the optical measuring system.展开更多
Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase a...Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring(A-EMS)technique under different conditions.The effects of stirring current,pouring temperature and stirring time on microstructural evolution,mean particle size,shape factor and solid fraction were investigated.The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity.The filling behavior and mechanical properties of parts were studied.Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of~27μm and a shape factor of~0.8 was achieved at the stirring current of 70 A,melt pouring temperature of 670℃,and stirring time of 30 s.Under these conditions,the step-die cavity was completely filled at die preheating temperature of 470℃.The hardness increases by decreasing step thickness as well as die preheating temperature.Moreover,the tensile properties are improved at lower die preheating temperatures.The fracture surface,which consists of a complex topography,indicates a typical ductile fracture.展开更多
The luminescence of EU^2＋ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from dif...The luminescence of EU^2＋ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from different Eu^2＋ sites in the lattice. When the BaB2O4 flux was applied, the intensity of the 398 nm emission was not clearly affected, but the intensity of the 515 nm emission was enhanced by about ten times. Gaussian fitting showed that the emission band at around 515 nm could actually be resolved into two bands with peak wavelengths of 499 nm and 521 nm, respectively. The assignments of the emission bands to the cation sites were carried out according to the values of bond valence. The overlapping of the 398 nm emission band on the excitation band of 515 nm emission implied that energy transfer could occur from the luminescent center related to the 398 nm emission to the center related to the 515 nm emission, and the energy transfer process remarkably enhanced the intensity of the 515 nm emission band. The phosphor had strong excitation at around 350-400 nm and emitted a bright green luminescence. Thus it could have applications as a green component in solid-state lighting devices assembled by near-UV Light Emitting Diodes （LED） combined with tricolor phosphors.展开更多
Dissolved black carbon(DBC)includes the water-soluble component of black carbon and/or its degradation products.It is a hydrophobic organic compound due to its thick cyclic aromatic structure and can therefore be pres...Dissolved black carbon(DBC)includes the water-soluble component of black carbon and/or its degradation products.It is a hydrophobic organic compound due to its thick cyclic aromatic structure and can therefore be present as particulate DBC(PDBC)on suspended particulate matter or particulate organic matter.PDBC is not equivalent to particulate black carbon(PBC)and is thus often overlooked when researchers measure PBC in particulate matter using current conventional methods.Consequently,the amount of DBC in nature is likely underestimated in many studies and the reliability of current findings on the geochemical behavior of DBC is subject to challenge.In this study,we attempted to draw the solid-liquid partition coefficient(K_(d),PDBC/DBC)based on detailed data on PBC,DBC,particulate organic carbon,total suspended solids,dissolved polycyclic aromatic hydrocarbons,and particulate polycyclic aromatic hydrocarbons in the surface waters of the Bohai Sea.The obtained K_(d)was in the range of 0.018-0.072.Accordingly,the concentrations of PDBC were 1.637-6.449μg C L^(-1).The estimated inventory of PDBC on suspended particulate matter in the Bohai Sea was 2.049-8.194 Gg,which was lower than that of PBC(15.16 Gg)but of the same order of magnitude.These results indicate that PDBC is an important form of DBC in the Bohai Sea.Quantitative results of DBC fluxes between the dissolved and particulate phases will benefit our understanding of DBC transport and fates in the ocean.展开更多
A solid sustained-release energetic material sample,an eruption device and a complete test system were prepared further to analyse the combustion characteristics of solid sustainedrelease energetic materials.The high-...A solid sustained-release energetic material sample,an eruption device and a complete test system were prepared further to analyse the combustion characteristics of solid sustainedrelease energetic materials.The high-temperature heat flux generated by the combustion of the samples from the eruption device was used to penetrate the Q235 target plate.In addition,the meaning and calculation formula of energy density characterising the all-around performance of heat flux were proposed.The numerical simulation of the combustion effect of samples was carried out.According to the data comparison,the numerical simulation results agreed with the experimental results,and the maximum deviation between the two was less than 8.9%.In addition,the structure of the combustion wave and high-temperature jet was proposed and analysed.Based on theoretical analysis,experimental research and numerical simulation,the theoretical burning rate formula of the sample was established.The maximum error between the theoretically calculated mass burning rate and the experimental results was less than 9.8%.Therefore,using the gas-phase steady-state combustion model to study the combustion characteristics of solid sustained-release energetic materials was reasonable.The theoretical burning rate formula also had high accuracy.Therefore,the model could provide scientific and academic guidance for the theoretical research,system design and practical application of solid sustained-release energetic materials in related fields.展开更多
When a thin laser crystal disk is used with a nearly flat-top pump profile, the heat flux can be considered to be one-dimensional. This results in a homogeneous temperature and stress profile within the laser medium l...When a thin laser crystal disk is used with a nearly flat-top pump profile, the heat flux can be considered to be one-dimensional. This results in a homogeneous temperature and stress profile within the laser medium leading to reduction of thermal effects. A nearly flat-top pump profile is achieved with a two-pass cylindrical-lens coupling system. An average output power of 550 W is obtained by an average pumping power of 1650 W with a 40-mm diameter Nd：YAG disk. The optical-optical efficiency is 33%.展开更多
文摘In this study, two types of pre-distributors (nonuniform-pores and dual-baffle)for the combined solids-liquid distributor in gas-liquid-solid circulating fluidized bed heat exchanger, were designed and the characteristics of particles distribution was compared. In the experiments, the sampling method was used to measure local solids flux and a U shape pipe was used to measure static pressure drop in the lower pipe box.The effects of different superficial liquid velocities and liquid viscosities on the parameters mentioned above were investigated.The degree of distribution of local solids flux in exchanger pipe was evaluated by the non-uniformity function.The results showed that the two types of pre-distributors were both suitable for gas-liquid-solid circulating fluidized bed heat exchanger at a lower static pressure drop in the lower pipe box.Compared with the nonuniform-pores pre-distributor, the dual-baffle pre-distributor showed better performance.
文摘Previous works have shown that the suction probe cannot be used to accurately measure the upward and downward particle fluxes independently. A new method using a single optical probe to measure the local solid flux is presented. The measurement of upward, downward and net solid fluxes was carried out in a cold model circulating fluidized bed (CFB) unit. The result shows that the profile of the net solid flux is in good agreement with the previous experimental data measured with a suction probe. The comparison between the average solid flux determined with the optical measuring system and the external solid flux was made, and the maximum deviationturned out to be 22%, with the average error being about 6.9%. These confirm that the optical fiber system can be successfully used to measure the upward, downward and net solid fluxes simultaneously by correctly processing the sampling signals obtained from the optical measuring system.
基金Central Applied Research Laboratory(CARL)Center of Materials ResearchDepartment of Materials Science and Metallurgy,Shahid Bahonar University of Kerman(SBUK)for support of this work。
文摘Nowadays,having an effective technique in preparing semi-solid slurries for rheocasting process seems to be an essential requirement.In this study,semi-solid slurry of A356 aluminum alloy was prepared by three-phase annular electromagnetic stirring(A-EMS)technique under different conditions.The effects of stirring current,pouring temperature and stirring time on microstructural evolution,mean particle size,shape factor and solid fraction were investigated.The rheocasting process was carried out by using a drop weight setup and to inject the prepared semi-solid slurry in optimal conditions into the step-die cavity.The filling behavior and mechanical properties of parts were studied.Microstructural evolution showed that the best semi-solid slurry which had fine spherical particles with the average size of~27μm and a shape factor of~0.8 was achieved at the stirring current of 70 A,melt pouring temperature of 670℃,and stirring time of 30 s.Under these conditions,the step-die cavity was completely filled at die preheating temperature of 470℃.The hardness increases by decreasing step thickness as well as die preheating temperature.Moreover,the tensile properties are improved at lower die preheating temperatures.The fracture surface,which consists of a complex topography,indicates a typical ductile fracture.
基金Project supported by the State Key Program for Basic Research of China (G1998061306)the National Natural Science Foundation of China (20071003, 20221101)the High Tech. Research of Zhejiang Province (2003C31029)
文摘The luminescence of EU^2＋ in BaMgSiO4 with BaB2O4 as flux was studied. The emission spectrum of the phosphor consisted of two bands, peaking at about 398 nm and 515 nm, which were attributed to the emissions from different Eu^2＋ sites in the lattice. When the BaB2O4 flux was applied, the intensity of the 398 nm emission was not clearly affected, but the intensity of the 515 nm emission was enhanced by about ten times. Gaussian fitting showed that the emission band at around 515 nm could actually be resolved into two bands with peak wavelengths of 499 nm and 521 nm, respectively. The assignments of the emission bands to the cation sites were carried out according to the values of bond valence. The overlapping of the 398 nm emission band on the excitation band of 515 nm emission implied that energy transfer could occur from the luminescent center related to the 398 nm emission to the center related to the 515 nm emission, and the energy transfer process remarkably enhanced the intensity of the 515 nm emission band. The phosphor had strong excitation at around 350-400 nm and emitted a bright green luminescence. Thus it could have applications as a green component in solid-state lighting devices assembled by near-UV Light Emitting Diodes （LED） combined with tricolor phosphors.
基金supported by the National Natural Science Foundation of China(Grant No.42076205)。
文摘Dissolved black carbon(DBC)includes the water-soluble component of black carbon and/or its degradation products.It is a hydrophobic organic compound due to its thick cyclic aromatic structure and can therefore be present as particulate DBC(PDBC)on suspended particulate matter or particulate organic matter.PDBC is not equivalent to particulate black carbon(PBC)and is thus often overlooked when researchers measure PBC in particulate matter using current conventional methods.Consequently,the amount of DBC in nature is likely underestimated in many studies and the reliability of current findings on the geochemical behavior of DBC is subject to challenge.In this study,we attempted to draw the solid-liquid partition coefficient(K_(d),PDBC/DBC)based on detailed data on PBC,DBC,particulate organic carbon,total suspended solids,dissolved polycyclic aromatic hydrocarbons,and particulate polycyclic aromatic hydrocarbons in the surface waters of the Bohai Sea.The obtained K_(d)was in the range of 0.018-0.072.Accordingly,the concentrations of PDBC were 1.637-6.449μg C L^(-1).The estimated inventory of PDBC on suspended particulate matter in the Bohai Sea was 2.049-8.194 Gg,which was lower than that of PBC(15.16 Gg)but of the same order of magnitude.These results indicate that PDBC is an important form of DBC in the Bohai Sea.Quantitative results of DBC fluxes between the dissolved and particulate phases will benefit our understanding of DBC transport and fates in the ocean.
文摘A solid sustained-release energetic material sample,an eruption device and a complete test system were prepared further to analyse the combustion characteristics of solid sustainedrelease energetic materials.The high-temperature heat flux generated by the combustion of the samples from the eruption device was used to penetrate the Q235 target plate.In addition,the meaning and calculation formula of energy density characterising the all-around performance of heat flux were proposed.The numerical simulation of the combustion effect of samples was carried out.According to the data comparison,the numerical simulation results agreed with the experimental results,and the maximum deviation between the two was less than 8.9%.In addition,the structure of the combustion wave and high-temperature jet was proposed and analysed.Based on theoretical analysis,experimental research and numerical simulation,the theoretical burning rate formula of the sample was established.The maximum error between the theoretically calculated mass burning rate and the experimental results was less than 9.8%.Therefore,using the gas-phase steady-state combustion model to study the combustion characteristics of solid sustained-release energetic materials was reasonable.The theoretical burning rate formula also had high accuracy.Therefore,the model could provide scientific and academic guidance for the theoretical research,system design and practical application of solid sustained-release energetic materials in related fields.
基金This work was supported by the National "863" Program of China under Grant No. 2004AA821160.
文摘When a thin laser crystal disk is used with a nearly flat-top pump profile, the heat flux can be considered to be one-dimensional. This results in a homogeneous temperature and stress profile within the laser medium leading to reduction of thermal effects. A nearly flat-top pump profile is achieved with a two-pass cylindrical-lens coupling system. An average output power of 550 W is obtained by an average pumping power of 1650 W with a 40-mm diameter Nd：YAG disk. The optical-optical efficiency is 33%.
