Low-cost sensors are widely used to collect high-spatial-resolution particulate matter data that traditional reference monitoring devices cannot.In addition to the mass concentration,the number concentration and size ...Low-cost sensors are widely used to collect high-spatial-resolution particulate matter data that traditional reference monitoring devices cannot.In addition to the mass concentration,the number concentration and size distribution are also fundamental in determining the origin and hazard level of particulate pollution.Therefore,low-cost optical sensors have been improved to establish optical particle sizers(OPSs).In this study,a low-cost OPS,the Nova SDS029,is introduced,and it is evaluated in comparison to two reference instruments—the GRIMM 11-D and the TSI 3330.We first tested the sizing accuracy using polystyrene latex spheres.Then,we assessed the mass and number size distribution accuracy in three application scenarios:indoor smoking,ambient air quality,and mobile monitoring.The evaluations suggest that the low-cost SDS029 rivals research-grade optical sizers in many aspects.For example,(1)the particle diameters obtained with the SDS029 are close to the reference instruments(usually<10%)in the 0.3-5μm range;(2)the number of particles and mass concentration are highly correlated(r≥0.99)with the values obtained with the reference instruments;and(3)the SDS029 slightly underestimates the number concentration,but the derived PM_(2.5)values are closer to monitoring station than the reference instruments.The successful application of the SDS029 in multiple scenarios suggests that a plausible particle size distribution can be obtained in an easy and cost-efficient way.We believe that low-cost OPSs will increasingly be used to map the sources and risk levels of particles at the city scale.展开更多
The Taklamakan Desert in China is one of the major source regions for Asian dust particles.All balloon-borne measurements in this report were carried out in Dunhuang,in the Taklamakan Desert,during calm weather condit...The Taklamakan Desert in China is one of the major source regions for Asian dust particles.All balloon-borne measurements in this report were carried out in Dunhuang,in the Taklamakan Desert,during calm weather conditions.The aerosol number concentration,size distribution,mass concentration,and horizontal mass flux due to westerly wind were investigated.The measurements were performed on 17 August 2001,17 October 2001,11 January 2002,and 30 April 2002.Five channels(0.3,0.5,0.8,1.2,and 3.6μm in diameter)were used in the Optical Particle Counter for particle measurements.The aerosol number concentration in the winter season(11 January 2002)at 3–5 km was very high.Variation of free-tropospheric aerosols on 30 April 2002 was noticeable.A super-micron range was noticeable in the size distribution of all the measurements.Many variations in temperature and aerosol concentration were found at these inversion points.High values of estimated mass concentration of aerosols were frequently observed in the atmosphere near the ground(i.e.,1–2 km);and interestingly,relatively high concentrations were frequently detected above 2 km from the surface.Wind patterns observed using ERA-Interim data at 500 and 850 hPa showed that westerly winds dominated in the Taklamakan Desert during the observation period.The average horizontal mass flux of background Asian dust due to westerly wind was observed to fall within the range of 58.5–1219 tons km?2 d?1.Vertical profiles of aerosol number concentrations showed that significant transport of aerosols dominated in the westerly region(i.e.,4–7 km).展开更多
A recent study demonstrated advancements in quantum computing by applying it to address a non-Hermitian optical manipulation problem.The emergence of exceptional points and the dynamics of optically trapped single or ...A recent study demonstrated advancements in quantum computing by applying it to address a non-Hermitian optical manipulation problem.The emergence of exceptional points and the dynamics of optically trapped single or multiple particles were simulated using a quantum computing approach.展开更多
Fibrous-type flters are used to capture dust particles in mining and other occupations where personnel are exposed for prolonged periods.Dust cleansing devices including fooded-bed dust scrubbers use these mesh-type m...Fibrous-type flters are used to capture dust particles in mining and other occupations where personnel are exposed for prolonged periods.Dust cleansing devices including fooded-bed dust scrubbers use these mesh-type multi-layered flters.These flters trap dust particles efciently on their surface and inside their mesh.However,their continued operation leads to dust build-up and clogging.This results in increased resistance of the flter and lowered airfow rate through the scrubber.This could potentially enhance the exposure of the miners.A non-clogging self-cleaning impingement screen type dust flter was designed by the authors for use in mining and industrial dust cleansing applications.The flter guides dirt-laden air through rapidly turning paths which forces it to shed heavier particles.The particles impact one of the impermeable solid metallic flter surfaces and are removed from the airstream.A full cone water spray installed upstream prevents any surface buildup of dust.This paper summaried the computer models generated to show the flter operations and laboratory experiments including optical particle counting to establish the cleaning efciency.展开更多
BACKGROUND Transmission of severe acute respiratory syndrome coronavirus 2 can occur during aerosol generating procedures.Several steps in spinal fusion may aerosolize blood but little data exists to quantify the risk...BACKGROUND Transmission of severe acute respiratory syndrome coronavirus 2 can occur during aerosol generating procedures.Several steps in spinal fusion may aerosolize blood but little data exists to quantify the risk this may confer upon surgeons.Aerosolized particles containing infectious coronavirus are typically 0.5-8.0μm.AIM To measure the generation of aerosols during spinal fusion using a handheld optical particle sizer(OPS).METHODS We quantified airborne particle counts during five posterior spinal instrumentation and fusions(9/22/2020-10/15/2020)using an OPS near the surgical field.Data were analyzed by 3 particle size groups:0.3-0.5μm/m^(3),1.0-5.0μm/m^(3),and 10.0μm/m^(3).We used hierarchical logistic regression to model the odds of a spike in aerosolized particle counts based on the step in progress.A spike was defined as a>3 standard deviation increase from average baseline levels.RESULTS Upon univariate analysis,bovie(P<0.0001),high speed pneumatic burring(P=0.009),and ultrasonic bone scalpel(P=0.002)were associated with increased 0.3-0.5μm/m^(3)particle counts relative to baseline.Bovie(P<0.0001)and burring(P<0.0001)were also associated with increased 1-5μm/m^(3)and 10μm/m^(3)particle counts.Pedicle drilling was not associated with increased particle counts in any of the size ranges measured.Our logistic regression model demonstrated that bovie(OR=10.2,P<0.001),burring(OR=10.9,P<0.001),and bone scalpel(OR=5.9,P<0.001)had higher odds of a spike in 0.3-0.5μm/m^(3)particle counts.Bovie(OR=2.6,P<0.001),burring(OR=5.8,P<0.001),and bone scalpel(OR=4.3,P=0.005)had higher odds of a spike in 1-5μm/m^(3)particle counts.Bovie(OR=0.3,P<0.001)and drilling(OR=0.2,P=0.011)had significantly lower odds of a spike in 10μm/m^(3)particle counts relative to baseline.CONCLUSION Several steps in spinal fusion are associated with increased airborne particle counts in the aerosol size range.Further research is warranted to determine if such particles have the potential to contain infectious viruses.Previous research has shown that electrocautery smoke may be an inhalation hazard for surgeons but here we show that usage of the bone scalpel and high-speed burr also have the potential to aerosolize blood.展开更多
The generation and observation of coherent THz synchrotron radiation from femtosecond electron bunches in the Shanghai Institute of Applied Physics femtosecond accelerator device is reported. We describe the experimen...The generation and observation of coherent THz synchrotron radiation from femtosecond electron bunches in the Shanghai Institute of Applied Physics femtosecond accelerator device is reported. We describe the experiment setup and present the first result of THz radiation properties such as power and spectrum.展开更多
Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the targ...Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the target experience the electrostatic fields caused by both the radiation pressure driven shock and the target normal sheath at the rear side of the target. A quasimonoenergetic proton bunch with central energy of about 11MeV and energy spread of ＆#8710; ε/ε about 0.18 is achieved by using a 3.45×1019 W/cm2, 66fs laser pulse. A comparison with the case of linearly polarized laser pulse and the same target condition is considered.展开更多
To obtain a real-time image of atmospheric particulate matter (PM) in highly polluted areas and to understand how the anthropogenic component linked to urban activities (industrial activities, domestic heating, road t...To obtain a real-time image of atmospheric particulate matter (PM) in highly polluted areas and to understand how the anthropogenic component linked to urban activities (industrial activities, domestic heating, road traffic, waste disposal) can locally affect near-surface measurement of PM, several measurement campaigns were achieved in the Campania region (Southern Italy) using both Lidar and in-situ instruments. A comparison between the obtained results highlights a good correlation between the data and the potential of remote sensing instruments for air quality monitoring. Data analysis was performed in terms of particle backscattering coefficient profile at 355 nm, PM mass concentration, and size distribution. Wind profiles, which covered a range of altitudes from 40 m to 290 m, were also used to study sources and physical processes involved. Measurement carried out in a rural area with a landfill site highlighted the presence of a homogeneous particulate layer throughout the sounded area due to winds driving aerosol from the landfill to the surrounding areas. The size distribution in mass concentration, highlighted a modal diameter moving towards 0.9 and 2 μm with a larger mass concentration of particles in the morning, before noon and in the afternoon when a large number of trucks delivered solid wastes. Moreover, large concentrations of particulate matter were measured in a small urban town with few industrial activities which peak (211 ± 33 μg·m<sup>-</sup><sup>3</sup>) was measured in the direction of the most urbanized area, probably due to the lighting of the domestic heating systems. Bimodal size distribution in number concentration was measured, indicative of two types of atmospheric particles sources: gas and liquid combustion (particles with sizes below 80 nm), including vehicular traffic and domestic gas-heating, and biomass combustion (particles with sizes of the order of 200 - 500 nm). Finally, data collected in a highly populated and industrialized area highlights the presence of particles having a high level of spherical geometry (aerosol depolarization below 5%) pointing towards the industrial area. Conversely, the measurements performed pointing toward other directions highlighted a diffused source of aspherical particles (depolarization values of about 3%) spreading throughout all city territory. The work showed as the co-location of remote sensing and near surface instruments is a promising approach to studying aerosol properties in the atmospheric layers and has more accurate information on atmospheric dynamics. Moreover, the correlation between the obtained results highlighted the potential of remote sensing instruments for air quality monitoring.展开更多
A model for measuring aerosol mass concentration by an optical particle counter is presented using the conception of the average mass. In this model, to understand the meaning of the pulse height distribution of parti...A model for measuring aerosol mass concentration by an optical particle counter is presented using the conception of the average mass. In this model, to understand the meaning of the pulse height distribution of particles which is used to inverse mass concentration, the relationship among intensity distribution in the optical sensing volume, particle shape, and the pulse height distribution is discussed. To solve the instability of the equivalent factor, a novel two-step calibration method is proposed. The experimental results demonstrate that mass concentrations calculated by the model are in good agreement with those measured by a norm-referenced instrument. For samples of soot and air, the slopes of fitting lines of data points are 0.9582 and 0.9220, and the correlation coefficients are 0.9991 and 0.9965, respectively.展开更多
This study presents the development of a medium flow, multiple slit based PM2.5 （particle aerodynamic diameter 〈2.5 μm） inertial impactor. Its performance was compared with that of a light scattering based optical...This study presents the development of a medium flow, multiple slit based PM2.5 （particle aerodynamic diameter 〈2.5 μm） inertial impactor. Its performance was compared with that of a light scattering based optical particle sizer in a field study and in controlled lab based experiments using polydisperse dolomite powder as test aerosol. The impactor＇s optimum nozzle configuration had a cutoff size of 2.51 μm （aero- dynamic diameter） at an operating flow rate of 215 L/rain with a pressure drop of 0.35 kPa across the impactor stage. Because the apparent particle density of an ambient aerosol depends on the physical properties and the chemical composition of the particles, the PM2.5 mass concentration was measured with an optical particle sizer and an inertial impactor over a weekday and a weekend day in a field study during which the effective particle shape factor and density were in tandem modified in order to com- pare the results from the two sampling techniques. The correlation of the two instrument results tended towards 1：1 with increasing values of shape factor （irregular shaped） and effective particle density. This observation was supported through chemical investigations of the collected mass, which showed a higher percentage contribution from elements which are mostly of crustal nature （namely, Ca, Fe, and Mg）.展开更多
In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical bea...In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical beam. By using this arbitrary beam theory, we systematically investigate the optical forces exerted on the graphene-coated particle by a focused Gaussian beam. Via tuning the chemical potential of the graphene, the optical force spectra could be modulated accordingly at resonant excitation. The hybridized whispering gallery mode of the electromagnetic field inside the graphene-coated polystyrene particle is more intensively localized than the pure polystyrene particle, which leads to a weakened morphology-dependent resonance in the optical forces. These investigations could open new perspectives for dynamic engineering of optical manipulations in optical tweezers applications.展开更多
This Letter reports the formation of periodic surface structures on Ni–Fe film irradiated by a single femtosecond laser pulse. A concave lens with a focus length of-150 mm is placed in front of an objective（100×...This Letter reports the formation of periodic surface structures on Ni–Fe film irradiated by a single femtosecond laser pulse. A concave lens with a focus length of-150 mm is placed in front of an objective（100×, NA=0.9）,which transforms the Gaussian laser field into a ring distribution by the Fresnel diffraction. Periodic ripples form on the ablation area after the irradiation of a single femtosecond laser pulse, which depends on the laser polarization and laser fluence. We propose that the ring structure of the laser field leads to a similar transient distribution of the permittivity on the sample surface, which further launches the surface plasmon polaritons. The interaction of the incident laser with surface plasmon polaritons dominates the formation of periodic surface structures.展开更多
We propose and analyze a long-range dielectric-loaded surface plasmon polariton （SPP） waveguide based on graded-index ridge over server millimeter distances. Then the influence of the dielectric thickness and the ri...We propose and analyze a long-range dielectric-loaded surface plasmon polariton （SPP） waveguide based on graded-index ridge over server millimeter distances. Then the influence of the dielectric thickness and the ridge refractive index on propagation length and mode width is discussed and simulated with the finite ele- ment raethod. The result shows that the SPP can propagate as long as 3.42 mm, as well as the mode width keeping as 1.64μm, a better one compared with the fixed refractive index. Considering its nanoscale dimension and outstanding performance, the structure is easily realized when connected with electrodes.展开更多
Particulate mass concentration (PM10, PM2.5), aerosol number concentration (NOPC), aerosol size distribu-tion and atmospheric visibility were simultaneously measured in Beijing in the summer and winter of 2001. From t...Particulate mass concentration (PM10, PM2.5), aerosol number concentration (NOPC), aerosol size distribu-tion and atmospheric visibility were simultaneously measured in Beijing in the summer and winter of 2001. From the profuse data collected, the following conclusions can be drown: (1) there are two peaks for the average diurnal variations of PM10 and NOPC in the summer, an obvious valley can be seen between 12:30 and 15:00 for their average diurnal variation in the winter; (2) there is one single peak for the average diurnal variation of atmospheric visibility in the summer, while there are two peaks in the winter; (3) PM10 and NOPC are usually smaller in the summer than those in the winter; (4) the average visibility is much lower during 00:00~09:00 in the summer than that in the winter, because of the very high relative humidity and higher concentration of the large particles (r>1.25 mm) in the summer during the period; (5) aerosol size distributions usually depend closely on season and relative humidity at the same place.展开更多
基金supported by the National Natural Science Foundation of China(No.42075182)。
文摘Low-cost sensors are widely used to collect high-spatial-resolution particulate matter data that traditional reference monitoring devices cannot.In addition to the mass concentration,the number concentration and size distribution are also fundamental in determining the origin and hazard level of particulate pollution.Therefore,low-cost optical sensors have been improved to establish optical particle sizers(OPSs).In this study,a low-cost OPS,the Nova SDS029,is introduced,and it is evaluated in comparison to two reference instruments—the GRIMM 11-D and the TSI 3330.We first tested the sizing accuracy using polystyrene latex spheres.Then,we assessed the mass and number size distribution accuracy in three application scenarios:indoor smoking,ambient air quality,and mobile monitoring.The evaluations suggest that the low-cost SDS029 rivals research-grade optical sizers in many aspects.For example,(1)the particle diameters obtained with the SDS029 are close to the reference instruments(usually<10%)in the 0.3-5μm range;(2)the number of particles and mass concentration are highly correlated(r≥0.99)with the values obtained with the reference instruments;and(3)the SDS029 slightly underestimates the number concentration,but the derived PM_(2.5)values are closer to monitoring station than the reference instruments.The successful application of the SDS029 in multiple scenarios suggests that a plausible particle size distribution can be obtained in an easy and cost-efficient way.We believe that low-cost OPSs will increasingly be used to map the sources and risk levels of particles at the city scale.
基金supported by the National Natural Science Foundations of China [grant numbers 41590871 and 41475136]the International Science&Technology Cooperation Program of China [grant number 2013DFG22820]
文摘The Taklamakan Desert in China is one of the major source regions for Asian dust particles.All balloon-borne measurements in this report were carried out in Dunhuang,in the Taklamakan Desert,during calm weather conditions.The aerosol number concentration,size distribution,mass concentration,and horizontal mass flux due to westerly wind were investigated.The measurements were performed on 17 August 2001,17 October 2001,11 January 2002,and 30 April 2002.Five channels(0.3,0.5,0.8,1.2,and 3.6μm in diameter)were used in the Optical Particle Counter for particle measurements.The aerosol number concentration in the winter season(11 January 2002)at 3–5 km was very high.Variation of free-tropospheric aerosols on 30 April 2002 was noticeable.A super-micron range was noticeable in the size distribution of all the measurements.Many variations in temperature and aerosol concentration were found at these inversion points.High values of estimated mass concentration of aerosols were frequently observed in the atmosphere near the ground(i.e.,1–2 km);and interestingly,relatively high concentrations were frequently detected above 2 km from the surface.Wind patterns observed using ERA-Interim data at 500 and 850 hPa showed that westerly winds dominated in the Taklamakan Desert during the observation period.The average horizontal mass flux of background Asian dust due to westerly wind was observed to fall within the range of 58.5–1219 tons km?2 d?1.Vertical profiles of aerosol number concentrations showed that significant transport of aerosols dominated in the westerly region(i.e.,4–7 km).
文摘A recent study demonstrated advancements in quantum computing by applying it to address a non-Hermitian optical manipulation problem.The emergence of exceptional points and the dynamics of optically trapped single or multiple particles were simulated using a quantum computing approach.
基金Funding The authors acknowledge the National Institute for Occupational Safety and Health(NIOSH)for funding this research project.
文摘Fibrous-type flters are used to capture dust particles in mining and other occupations where personnel are exposed for prolonged periods.Dust cleansing devices including fooded-bed dust scrubbers use these mesh-type multi-layered flters.These flters trap dust particles efciently on their surface and inside their mesh.However,their continued operation leads to dust build-up and clogging.This results in increased resistance of the flter and lowered airfow rate through the scrubber.This could potentially enhance the exposure of the miners.A non-clogging self-cleaning impingement screen type dust flter was designed by the authors for use in mining and industrial dust cleansing applications.The flter guides dirt-laden air through rapidly turning paths which forces it to shed heavier particles.The particles impact one of the impermeable solid metallic flter surfaces and are removed from the airstream.A full cone water spray installed upstream prevents any surface buildup of dust.This paper summaried the computer models generated to show the flter operations and laboratory experiments including optical particle counting to establish the cleaning efciency.
文摘BACKGROUND Transmission of severe acute respiratory syndrome coronavirus 2 can occur during aerosol generating procedures.Several steps in spinal fusion may aerosolize blood but little data exists to quantify the risk this may confer upon surgeons.Aerosolized particles containing infectious coronavirus are typically 0.5-8.0μm.AIM To measure the generation of aerosols during spinal fusion using a handheld optical particle sizer(OPS).METHODS We quantified airborne particle counts during five posterior spinal instrumentation and fusions(9/22/2020-10/15/2020)using an OPS near the surgical field.Data were analyzed by 3 particle size groups:0.3-0.5μm/m^(3),1.0-5.0μm/m^(3),and 10.0μm/m^(3).We used hierarchical logistic regression to model the odds of a spike in aerosolized particle counts based on the step in progress.A spike was defined as a>3 standard deviation increase from average baseline levels.RESULTS Upon univariate analysis,bovie(P<0.0001),high speed pneumatic burring(P=0.009),and ultrasonic bone scalpel(P=0.002)were associated with increased 0.3-0.5μm/m^(3)particle counts relative to baseline.Bovie(P<0.0001)and burring(P<0.0001)were also associated with increased 1-5μm/m^(3)and 10μm/m^(3)particle counts.Pedicle drilling was not associated with increased particle counts in any of the size ranges measured.Our logistic regression model demonstrated that bovie(OR=10.2,P<0.001),burring(OR=10.9,P<0.001),and bone scalpel(OR=5.9,P<0.001)had higher odds of a spike in 0.3-0.5μm/m^(3)particle counts.Bovie(OR=2.6,P<0.001),burring(OR=5.8,P<0.001),and bone scalpel(OR=4.3,P=0.005)had higher odds of a spike in 1-5μm/m^(3)particle counts.Bovie(OR=0.3,P<0.001)and drilling(OR=0.2,P=0.011)had significantly lower odds of a spike in 10μm/m^(3)particle counts relative to baseline.CONCLUSION Several steps in spinal fusion are associated with increased airborne particle counts in the aerosol size range.Further research is warranted to determine if such particles have the potential to contain infectious viruses.Previous research has shown that electrocautery smoke may be an inhalation hazard for surgeons but here we show that usage of the bone scalpel and high-speed burr also have the potential to aerosolize blood.
文摘The generation and observation of coherent THz synchrotron radiation from femtosecond electron bunches in the Shanghai Institute of Applied Physics femtosecond accelerator device is reported. We describe the experiment setup and present the first result of THz radiation properties such as power and spectrum.
基金Supported by the National Key Basic Research Program of China under Grant No 2006CB806004, the National Natural Science Foundation of China under Grant Nos 10675155 and 10834008, Scientific Research Foundation for Awarder of Excellent Doctor Thesis, and President Award of Chinese Academy of Sciences （No 0801051-X00）.
文摘Two dimensional particle-in-cell simulations are taken to study the interaction of a circularly polarized laser pulse with a nano-scale micro-structured target. The protons which are doped in the rear side of the target experience the electrostatic fields caused by both the radiation pressure driven shock and the target normal sheath at the rear side of the target. A quasimonoenergetic proton bunch with central energy of about 11MeV and energy spread of ＆#8710; ε/ε about 0.18 is achieved by using a 3.45×1019 W/cm2, 66fs laser pulse. A comparison with the case of linearly polarized laser pulse and the same target condition is considered.
文摘To obtain a real-time image of atmospheric particulate matter (PM) in highly polluted areas and to understand how the anthropogenic component linked to urban activities (industrial activities, domestic heating, road traffic, waste disposal) can locally affect near-surface measurement of PM, several measurement campaigns were achieved in the Campania region (Southern Italy) using both Lidar and in-situ instruments. A comparison between the obtained results highlights a good correlation between the data and the potential of remote sensing instruments for air quality monitoring. Data analysis was performed in terms of particle backscattering coefficient profile at 355 nm, PM mass concentration, and size distribution. Wind profiles, which covered a range of altitudes from 40 m to 290 m, were also used to study sources and physical processes involved. Measurement carried out in a rural area with a landfill site highlighted the presence of a homogeneous particulate layer throughout the sounded area due to winds driving aerosol from the landfill to the surrounding areas. The size distribution in mass concentration, highlighted a modal diameter moving towards 0.9 and 2 μm with a larger mass concentration of particles in the morning, before noon and in the afternoon when a large number of trucks delivered solid wastes. Moreover, large concentrations of particulate matter were measured in a small urban town with few industrial activities which peak (211 ± 33 μg·m<sup>-</sup><sup>3</sup>) was measured in the direction of the most urbanized area, probably due to the lighting of the domestic heating systems. Bimodal size distribution in number concentration was measured, indicative of two types of atmospheric particles sources: gas and liquid combustion (particles with sizes below 80 nm), including vehicular traffic and domestic gas-heating, and biomass combustion (particles with sizes of the order of 200 - 500 nm). Finally, data collected in a highly populated and industrialized area highlights the presence of particles having a high level of spherical geometry (aerosol depolarization below 5%) pointing towards the industrial area. Conversely, the measurements performed pointing toward other directions highlighted a diffused source of aspherical particles (depolarization values of about 3%) spreading throughout all city territory. The work showed as the co-location of remote sensing and near surface instruments is a promising approach to studying aerosol properties in the atmospheric layers and has more accurate information on atmospheric dynamics. Moreover, the correlation between the obtained results highlighted the potential of remote sensing instruments for air quality monitoring.
基金the Doctor Creation Foundation of Nanjing University of Science and Technology
文摘A model for measuring aerosol mass concentration by an optical particle counter is presented using the conception of the average mass. In this model, to understand the meaning of the pulse height distribution of particles which is used to inverse mass concentration, the relationship among intensity distribution in the optical sensing volume, particle shape, and the pulse height distribution is discussed. To solve the instability of the equivalent factor, a novel two-step calibration method is proposed. The experimental results demonstrate that mass concentrations calculated by the model are in good agreement with those measured by a norm-referenced instrument. For samples of soot and air, the slopes of fitting lines of data points are 0.9582 and 0.9220, and the correlation coefficients are 0.9991 and 0.9965, respectively.
文摘This study presents the development of a medium flow, multiple slit based PM2.5 （particle aerodynamic diameter 〈2.5 μm） inertial impactor. Its performance was compared with that of a light scattering based optical particle sizer in a field study and in controlled lab based experiments using polydisperse dolomite powder as test aerosol. The impactor＇s optimum nozzle configuration had a cutoff size of 2.51 μm （aero- dynamic diameter） at an operating flow rate of 215 L/rain with a pressure drop of 0.35 kPa across the impactor stage. Because the apparent particle density of an ambient aerosol depends on the physical properties and the chemical composition of the particles, the PM2.5 mass concentration was measured with an optical particle sizer and an inertial impactor over a weekday and a weekend day in a field study during which the effective particle shape factor and density were in tandem modified in order to com- pare the results from the two sampling techniques. The correlation of the two instrument results tended towards 1：1 with increasing values of shape factor （irregular shaped） and effective particle density. This observation was supported through chemical investigations of the collected mass, which showed a higher percentage contribution from elements which are mostly of crustal nature （namely, Ca, Fe, and Mg）.
基金supported by the National 973 Program of China(Nos.2013CB632704 and 2013CB922404)the National Natural Science Foundation of China(Nos.11374357,61475186,and 11434017)
文摘In this paper, we derive the analytical expression for the multipole expansion coefficients of scattering and interior fields of a graphene-coated dielectric particle under the illumination of an arbitrary optical beam. By using this arbitrary beam theory, we systematically investigate the optical forces exerted on the graphene-coated particle by a focused Gaussian beam. Via tuning the chemical potential of the graphene, the optical force spectra could be modulated accordingly at resonant excitation. The hybridized whispering gallery mode of the electromagnetic field inside the graphene-coated polystyrene particle is more intensively localized than the pure polystyrene particle, which leads to a weakened morphology-dependent resonance in the optical forces. These investigations could open new perspectives for dynamic engineering of optical manipulations in optical tweezers applications.
基金supported by the National Natural Science Foundation of China (Nos. 11474097, 11274116, 11104178, 44108280, and 51132004)the National Special Science Research Program of China (No. 2011CB808105)
文摘This Letter reports the formation of periodic surface structures on Ni–Fe film irradiated by a single femtosecond laser pulse. A concave lens with a focus length of-150 mm is placed in front of an objective（100×, NA=0.9）,which transforms the Gaussian laser field into a ring distribution by the Fresnel diffraction. Periodic ripples form on the ablation area after the irradiation of a single femtosecond laser pulse, which depends on the laser polarization and laser fluence. We propose that the ring structure of the laser field leads to a similar transient distribution of the permittivity on the sample surface, which further launches the surface plasmon polaritons. The interaction of the incident laser with surface plasmon polaritons dominates the formation of periodic surface structures.
基金supported by the National Natural Science Foundation of China(Nos.61275201 and 61372037)the Beijing Excellent Ph.D.Thesis Guidance Foundation(No.20131001301)+1 种基金the Fund of State Key Laboratory of Information Photonics and Optical Communications(Beijing University of Posts and Telecommunications)the Opened Fund of the State Key Laboratory on Integrated Optoelectronics,Institute of Semiconductors,Chinese Academy of Sciences
文摘We propose and analyze a long-range dielectric-loaded surface plasmon polariton （SPP） waveguide based on graded-index ridge over server millimeter distances. Then the influence of the dielectric thickness and the ridge refractive index on propagation length and mode width is discussed and simulated with the finite ele- ment raethod. The result shows that the SPP can propagate as long as 3.42 mm, as well as the mode width keeping as 1.64μm, a better one compared with the fixed refractive index. Considering its nanoscale dimension and outstanding performance, the structure is easily realized when connected with electrodes.
文摘Particulate mass concentration (PM10, PM2.5), aerosol number concentration (NOPC), aerosol size distribu-tion and atmospheric visibility were simultaneously measured in Beijing in the summer and winter of 2001. From the profuse data collected, the following conclusions can be drown: (1) there are two peaks for the average diurnal variations of PM10 and NOPC in the summer, an obvious valley can be seen between 12:30 and 15:00 for their average diurnal variation in the winter; (2) there is one single peak for the average diurnal variation of atmospheric visibility in the summer, while there are two peaks in the winter; (3) PM10 and NOPC are usually smaller in the summer than those in the winter; (4) the average visibility is much lower during 00:00~09:00 in the summer than that in the winter, because of the very high relative humidity and higher concentration of the large particles (r>1.25 mm) in the summer during the period; (5) aerosol size distributions usually depend closely on season and relative humidity at the same place.
