In this study,the particle size-resolved distribution from a China-3 certificated light-duty diesel vehicle was measured by using a portable emission measurement system（PEMS）.In order to examine the influences of ve...In this study,the particle size-resolved distribution from a China-3 certificated light-duty diesel vehicle was measured by using a portable emission measurement system（PEMS）.In order to examine the influences of vehicle specific power（VSP） and high-altitude operation,measurements were conducted at 8 constant speeds,which ranged from 10 to 80 km/hr at10 km/hr intervals,and two different high altitudes,namely 2200 and 3200 m.The results demonstrated that the numbers of particles in all size ranges decreased significantly as VSP increased when the test vehicle was running at lower speeds（〈 20 km/hr）,while at a moderate speed（between 30 and 60 km/hr）,the particle number was statistically insensitive to increase VSP.Under high-speed cruising conditions,the numbers of ultrafine particles and PM2.5were insensitive to changes in VSP,but the numbers of nanoparticles and PM10 surged considerably.An increase in the operational altitude of the test vehicle resulted in increased particle number emissions at low and high driving speeds;however,particle numbers obtained at moderate speeds decreased as altitude rose.When the test vehicle was running at moderate speeds,particle numbers measured at the two altitudes were very close,except for comparatively higher number concentrations of nanoparticles measured at 2200 m.展开更多
The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofD = 240mm. The effect...The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofD = 240mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution （PSD） were investigated, d43 and PSD were measured online using a Malvern Insitec Liquid Pro- cess Sizer every 20 s. It was found that d43 varied between 13 kwh and 26 lain under different operating conditions, and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.展开更多
As the main use of TBM(tunnel boring machine)cutter ring(DC53 steel)currently is difficult to meet the requirements of high wear resistance and high toughness synchronously in its service environment,a new HWR0 steel ...As the main use of TBM(tunnel boring machine)cutter ring(DC53 steel)currently is difficult to meet the requirements of high wear resistance and high toughness synchronously in its service environment,a new HWR0 steel with 4%Cr-3%V for TBM cutter ring has been developed to control carbides in steel.Precipitation behavior of carbides in HWR0 steel was investigated through theoretical calculation by Thermo-Calc and experimental measurement using scanning electron microscope,energy dispersive spectrometer,electron probe X-ray micro-analyzer,and laser particle size analyzer.The results show that three different carbides are precipitated during cooling.And the as-cast electroslag remelting ingot of HWR0 steel primarily consists of many blocky or strip-like MC distributed along grain boundaries,few chrysanthemum-like M_(6)C concentrated at grain boundary intersections,and a large quantity of fine M_(23)C_(6)and M_(6)C dispersed in the matrix.Compared with DC53 steel,HWR0 steel has more high-hardness carbides MC,which are discontinuously distributed at the grain boundaries,achieving the dual improvement of wear resistance and impact toughness.Cooling rates significantly influence the carbides distribution and grain size.A slower cooling rate exacerbates the segregation of alloying elements,which leads to the localized enrichment of Mo and the subsequent precipitation of M_(6)C carbides at grain boundary intersections.In contrast,faster cooling rate decreases the element segregation,promotes carbide nucleation and limits the space for carbides growth,which results in finer size and distribution of carbides and grains.Higher cooling rates yield a more homogeneous microstructure with uniform MC compositions and promote the preferential formation of M_(6)C carbides along grain boundaries,which enhances the mechanical properties.展开更多
A modified regularization algorithm with a more proper operator was proposed for the inversion of particle size distribution （PSD） from light-scattering data in a laser particle sizer based on the Mie scattering pri...A modified regularization algorithm with a more proper operator was proposed for the inversion of particle size distribution （PSD） from light-scattering data in a laser particle sizer based on the Mie scattering principle. The Generalized Cross-Validation （GCV） method and the L-curve method were used for deter- mining the regularization parameter. The Successive Over-Relaxation （SOR） iterative method was used to increase the exactness and stability of the converged result. The simulated results based on the modified algorithm are in a good agreement with the experimental data measured for nine standard particulate samples, their mixtures as well as three natural particulate materials with irregular shapes, indicating that this modified regularization method is not only feasible but also effective for the simulation of PSD from corresponding light-scattering data.展开更多
Size distributions of ambient aerosols at the Fresno Supersite were measured with four commercially available scanning mobility particle sizers （SMPS）. TSI nano, TSI standard, Grimm, and MSP instruments were colloca...Size distributions of ambient aerosols at the Fresno Supersite were measured with four commercially available scanning mobility particle sizers （SMPS）. TSI nano, TSI standard, Grimm, and MSP instruments were collocated at the Fresno Supersite and particle size distributions were measured continuously from August 18 through September 18, 2005. For particles with diameters between 10 and 200 nm, differences among hourly-average ambient particle concentrations ranged from 0% between the TSI nano and Grimm in the 30-50 nm size range to 39% between the Grimm and MSP in the 10-30 nm size range. MSP concentrations were 10-33% lower than those measured with the TSI standard for particles smaller than 200 nm. The TSI nano and TSI standard agreed to within 5% in their overlapping size range （10-84 nm）. The TSI nano and Grimm agreed to within 40% for 5-10 nm particles.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.51576016 and 51476012)
文摘In this study,the particle size-resolved distribution from a China-3 certificated light-duty diesel vehicle was measured by using a portable emission measurement system（PEMS）.In order to examine the influences of vehicle specific power（VSP） and high-altitude operation,measurements were conducted at 8 constant speeds,which ranged from 10 to 80 km/hr at10 km/hr intervals,and two different high altitudes,namely 2200 and 3200 m.The results demonstrated that the numbers of particles in all size ranges decreased significantly as VSP increased when the test vehicle was running at lower speeds（〈 20 km/hr）,while at a moderate speed（between 30 and 60 km/hr）,the particle number was statistically insensitive to increase VSP.Under high-speed cruising conditions,the numbers of ultrafine particles and PM2.5were insensitive to changes in VSP,but the numbers of nanoparticles and PM10 surged considerably.An increase in the operational altitude of the test vehicle resulted in increased particle number emissions at low and high driving speeds;however,particle numbers obtained at moderate speeds decreased as altitude rose.When the test vehicle was running at moderate speeds,particle numbers measured at the two altitudes were very close,except for comparatively higher number concentrations of nanoparticles measured at 2200 m.
基金the State Key Development Program for Basic Research of China(2013CB632601)the National High Technology Research and Development Program of China(2011AA060704)+1 种基金the National Natural Science Foundation of China(21476236,91434126)the National Science Fund for Distinguished Young Scholars(21025627)
文摘The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofD = 240mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution （PSD） were investigated, d43 and PSD were measured online using a Malvern Insitec Liquid Pro- cess Sizer every 20 s. It was found that d43 varied between 13 kwh and 26 lain under different operating conditions, and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.
基金financial support of the Central Guide Local Science and Technology Development Project of Hubei Province of China(No.2023EGA008)the Wuhan Natural Science Foundation Exploration Project(Chenguang Project)(No.2024040801020309).
文摘As the main use of TBM(tunnel boring machine)cutter ring(DC53 steel)currently is difficult to meet the requirements of high wear resistance and high toughness synchronously in its service environment,a new HWR0 steel with 4%Cr-3%V for TBM cutter ring has been developed to control carbides in steel.Precipitation behavior of carbides in HWR0 steel was investigated through theoretical calculation by Thermo-Calc and experimental measurement using scanning electron microscope,energy dispersive spectrometer,electron probe X-ray micro-analyzer,and laser particle size analyzer.The results show that three different carbides are precipitated during cooling.And the as-cast electroslag remelting ingot of HWR0 steel primarily consists of many blocky or strip-like MC distributed along grain boundaries,few chrysanthemum-like M_(6)C concentrated at grain boundary intersections,and a large quantity of fine M_(23)C_(6)and M_(6)C dispersed in the matrix.Compared with DC53 steel,HWR0 steel has more high-hardness carbides MC,which are discontinuously distributed at the grain boundaries,achieving the dual improvement of wear resistance and impact toughness.Cooling rates significantly influence the carbides distribution and grain size.A slower cooling rate exacerbates the segregation of alloying elements,which leads to the localized enrichment of Mo and the subsequent precipitation of M_(6)C carbides at grain boundary intersections.In contrast,faster cooling rate decreases the element segregation,promotes carbide nucleation and limits the space for carbides growth,which results in finer size and distribution of carbides and grains.Higher cooling rates yield a more homogeneous microstructure with uniform MC compositions and promote the preferential formation of M_(6)C carbides along grain boundaries,which enhances the mechanical properties.
基金supported by the Science and Technology Development Planning Program of the Guangzhou City Bureau of Scienceand Technology,China(grant200773-D2091)
文摘A modified regularization algorithm with a more proper operator was proposed for the inversion of particle size distribution （PSD） from light-scattering data in a laser particle sizer based on the Mie scattering principle. The Generalized Cross-Validation （GCV） method and the L-curve method were used for deter- mining the regularization parameter. The Successive Over-Relaxation （SOR） iterative method was used to increase the exactness and stability of the converged result. The simulated results based on the modified algorithm are in a good agreement with the experimental data measured for nine standard particulate samples, their mixtures as well as three natural particulate materials with irregular shapes, indicating that this modified regularization method is not only feasible but also effective for the simulation of PSD from corresponding light-scattering data.
基金sponsored by the California Air Resources Board (ARB) under DRI project number 04-307U.S. EPA's Supersites Program at Fresno
文摘Size distributions of ambient aerosols at the Fresno Supersite were measured with four commercially available scanning mobility particle sizers （SMPS）. TSI nano, TSI standard, Grimm, and MSP instruments were collocated at the Fresno Supersite and particle size distributions were measured continuously from August 18 through September 18, 2005. For particles with diameters between 10 and 200 nm, differences among hourly-average ambient particle concentrations ranged from 0% between the TSI nano and Grimm in the 30-50 nm size range to 39% between the Grimm and MSP in the 10-30 nm size range. MSP concentrations were 10-33% lower than those measured with the TSI standard for particles smaller than 200 nm. The TSI nano and TSI standard agreed to within 5% in their overlapping size range （10-84 nm）. The TSI nano and Grimm agreed to within 40% for 5-10 nm particles.
