Number Of Particles Research Articles

Long-term dynamics around the Didymos–Dimorphos binary asteroid of boulders ejected after the DART impact

Context. In 2022, the DART mission spacecraft impacted the asteroid Dimorphos, the secondary body of the binary Didymos system, ejecting a large number of dust particles, rocks and boulders. The ESA Hera mission will reach the system in 2026 for post-impact studies and a possible detection of orbiting fragments. Aims. We aim to investigate the long-term dynamics of the large boulders ejected by DART to test if any of these objects survive in orbit until the arrival of the Hera mission. Methods. To model the dynamics of the boulders, we used a numerical model that includes the gravity of non-spherical Didymos and Dimorphos, the solar gravity, and the radiation pressure. The SPICE kernels are used to define the correct reference frame for the integrations. Results. The dynamics of the boulders is highly chaotic, and 1% of the initial boulders survive at least for four years on quasi-stable orbits. These orbits are characterised by wide oscillations in eccentricity in antiphase with those in inclination (including spin flips), a mechanism similar to the Kozai one. This behaviour may protect these bodies from close encounters with both asteroids. We also computed the distribution on the surfaces of the asteroids of sesquinary impacts, which may influence the dust emission (after the initial DART impact) and the surface composition of the asteroids. Conclusions. The probability of observing boulders by the mission Hera is small but non-negligible, and an almost constant flux of escaping boulders is expected in the coming years since their lifetime after the DART impact covers a large time interval. Most re-impacts on Dimorphos occur in the hemisphere opposite the impact site, preferentially close to the equatorial plane.

Ion cyclotron emission in Maxwellian plasmas

Destabilization of ion cyclotron waves—waves with frequencies close to ion cyclotron harmonics—in inhomogeneous plasmas with Maxwell velocity distribution is considered. A new mechanism of destabilization of these waves is found, whereas the known interaction between cyclotron waves and drift waves is shown to be hardly able to lead to instabilities in realistic tokamak plasmas. Our finding is that the resonance wave–particle interaction in the presence of temperature gradient can change the diamagnetic drift frequency in such a way that the destabilizing influence of the diamagnetic drift exceeds Landau damping. This occurs when the energy of resonance particles is sufficiently high, which is always the case due to the infinite tail of the Maxwell distribution. Particles with higher energies provide a larger ratio of drive to damping, but the number of resonance particles and, thus, instability growth rates are exponentially small when particle energy is very high. Therefore, only moderately suprathermal particles can lead to observable instabilities. A condition for instabilities driven by these particles is obtained. Destabilization of electrostatic cyclotron waves and ordinary cyclotron waves is studied.

Disappearance of cobalt particles above nanocrystalline diamond films by HF-CVD on cemented tungsten carbide

Abstract In this study, the possibility of the disappearance of Co particles on the surface of nanocrystalline diamond (NCD) films with large thicknesses was examined. It is shown that the number of Co particles decreased clearly with larger thicknesses. In the thickest case, the Co particles disappeared almost completely. Investigation with energy-dispersive spectroscopy for the cross section of the NCD films suggested that the Co particle was embedded during the growth of the NCD film. Our observations will contribute to depositing smooth NCD films on tools without the embrittlement of substrates by Co etching.

Return Air Grille Position in a Cleanroom for Medicinal Packaging Using CFD Method

A cleanroom is a highly controlled environment; therefore, air quality is of significant concern, and specific physical and microbiological requirements must meet the standard. In addition to the number of particles, another critical parameter in a cleanroom is temperature. USP (The United States Pharmacopeia) 797 recommends that the temperature of a cleanroom be around 20 °C. Air quality is achieved through several parameters and components, such as using a high-efficiency particulate air filter (HEPA), the amount of fresh air entering the room, temperature, pressure difference, and airflow direction. In this study, the cooling load of the room for the filling and sealing process was calculated, and the airflow and temperature distribution patterns between two parameters of the return air grille (RAG) position were compared using Computational Fluid Dynamics (CFD). The first parameter, RAG 1, was placed above the ceiling, while the second parameter, RAG 2, was set on the sidewall. Based on the results of the study, it was found that the heat load generated from the room was 6.99 kW with a cooling coil capacity amounting to 10.77 kW. Moreover, the supply airflow rate was 371.66 l/s. Based on the results of the simulation modelling, it was found that the RAG positioned on the sidewall was more ideal than the RAG positioned above the ceiling since the temperature was more evenly distributed in the room where the RAG was positioned on the sidewall.

Migration trajectories and blocking effect of the fine particles in porous media based on particle flow simulation

The particle flow code method based on the discrete element method was used to establish the seepage migration model of fine particles [fine particles (FPs), i.e., suspended particles] in a porous medium. A series of numerical simulations were carried out by changing the particle size, seepage velocity, particle injection number, and wide particle size gradation. The research showed that large FPs play a major role in blocking porous medium channels when the injected FPs have a wide size gradation. Due to the blocking effect, small FPs that would not otherwise have deposited also deposit. Moreover, by increasing the number of large FPs in the mixed particles, the total number of particles deposited and the number of smaller FPs deposited will also increase. The distribution of FPs in porous mediums can be divided into three types: surface deposition, internal deposition, and non-deposition. When the seepage velocity increases and reaches a seepage threshold, which is the critical seepage velocity, the deposited FPs will once again be in a suspended state and undergo migration. On the contrary, the FPs will continue to maintain their sedimentary state, and the critical seepage velocity will also increase correspondingly with increasing particle size.

Slip topology of steady flows around a critical point: Taking the linear velocity field as an example

The flow of viscous fluids is considered as the aggregation of the motion of fluid particles when the fluid is conceived to be made up by an infinite number of particles. As an alternative of this conventional model, fluid motion could be understood as the slip of fluid layers with a molecular scale over each other, where the slip structures of fluid and their associated small-scale motion are characterized by an axial-vector-valued differential 1-form, called the vortex field. In this paper, in the case of steady flows we define the swirling degree of the velocity field at a point, and further the swirl field of the steady flow, to study the slip topology of fluid or the local streamline pattern around the critical point. The linear velocity field in the right real Schur form is used to carry out detailed analyses around the isolated critical point. Theoretical deduction and numerical test unveil the connection between the swirling degree and the swirl field, greatly make clear the topological property of slip structures of fluid in steady flows, especially in three-dimensional space.

The application of the "inverse problem" method for constructing confining potentials that make N-soliton waveforms exact solutions in the Gross-Pitaevskii equation.

In this work, we discuss an application of the "inverse problem" method to find the external trapping potential, which has particular N trapped soliton-like solutions of the Gross-Pitaevskii equation (GPE) also known as the cubic nonlinear Schrödinger equation (NLSE). This inverse method assumes particular forms for the trapped soliton wave function, which then determines the (unique) external (confining) potential. The latter renders these assumed waveforms exact solutions of the GPE (NLSE) for both attractive (g<0) and repulsive (g>0) self-interactions. For both signs of g, we discuss the stability with respect to self-similar deformations and translations. For g<0, a critical mass Mc or equivalently the number of particles for instabilities to arise can often be found analytically. On the other hand, for the case with g>0 corresponding to repulsive self-interactions which is often discussed in the atomic physics realm of Bose-Einstein condensates, the bound solutions are found to be always stable. For g<0, we also determine the critical mass numerically by using linear stability or Bogoliubov-de Gennes analysis, and compare these results with our analytic estimates. Various analytic forms for the trapped N-soliton solutions in one, two, and three spatial dimensions are discussed, including sums of Gaussians or higher-order eigenfunctions of the harmonic oscillator Hamiltonian.

Kinetic stability of Chapman–Enskog plasmas

In this paper, we investigate the kinetic stability of classical, collisional plasma – that is, plasma in which the mean-free-path $\lambda$ of constituent particles is short compared with the length scale $L$ over which fields and bulk motions in the plasma vary macroscopically, and the collision time is short compared with the evolution time. Fluid equations are typically used to describe such plasmas, since their distribution functions are close to being Maxwellian. The small deviations from the Maxwellian distribution are calculated via the Chapman–Enskog (CE) expansion in $\lambda /L \ll 1$ , and determine macroscopic momentum and heat fluxes in the plasma. Such a calculation is only valid if the underlying CE distribution function is stable at collisionless length scales and/or time scales. We find that at sufficiently high plasma $\beta$ , the CE distribution function can be subject to numerous microinstabilities across a wide range of scales. For a particular form of the CE distribution function arising in strongly magnetised plasma (viz. plasma in which the Larmor periods of particles are much smaller than collision times), we provide a detailed analytic characterisation of all significant microinstabilities, including peak growth rates and their associated wavenumbers. Of specific note is the discovery of several new microinstabilities, including one at sub-electron-Larmor scales (the ‘whisper instability’) whose growth rate in certain parameter regimes is large compared with other instabilities. Our approach enables us to construct the kinetic stability maps of classical, two-species collisional plasma in terms of $\lambda$ , the electron inertial scale $d_e$ and the plasma $\beta$ . This work is of general consequence in emphasising the fact that high- $\beta$ collisional plasmas can be kinetically unstable; for strongly magnetised CE plasmas, the condition for instability is $\beta \gtrsim L/\lambda$ . In this situation, the determination of transport coefficients via the standard CE approach is not valid.

Anharmonic effects on the squeezing of axion perturbations

It is assumed in standard cosmology that the Universe underwent a period of inflation in its earliest phase, providing the seeds for structure formation through vacuum fluctuations of the inflaton scalar field. These fluctuations get stretched by the quasi-exponential expansion of the Universe and become squeezed. The aim of this paper is to deepen the understanding of the squeezing process, considering the effect of self-interactions. Axion-like particles can provide a useful setup to study this effect. Specifically we focus on the consequences that a non-trivial evolution of the background axion field has on the squeezing of the perturbations. We follow the evolution of the axion's fluctuation modes from the horizon exit during inflation to the radiation-dominated epoch. We compute Bogoliubov coefficients and squeezing parameters, which are linked to the axion particle number and isocurvature perturbation. We find that the quantum mechanical particle production and the squeezing of the perturbations are enhanced, if one accounts for anharmonic effects, i.e., the effect of higher order terms in the potential. This effect becomes particularly strong towards the hilltop of the potential.

Chinese migrants exhibit impaired postprandial lipaemia compared to Caucasian counterparts following both high fat and high carbohydrate test meals.

People of Chinese ethnicity develop type 2 diabetes mellitus (T2DM) at a younger age and lower body mass index (BMI) than their Caucasian counterparts. Furthermore, Chinese migrants to Westernised countries have an increased risk of metabolic diseases compared to those in their country of origin(1,2). We propose that this increased risk is due to a greater manifestation of metabolic abnormalities in response to altered diet and lifestyle behaviours. Although fasting lipaemia and glycaemia are commonly used to predict risk of CVD and T2DM, assessment of impaired postprandial metabolism has been found to be a more sensitive indicator of risk(3). We hypothesised that Chinese migrants, at risk of T2DM, exhibit impaired postprandial lipid and lipoprotein metabolism compared to Australian-born Caucasian counterparts. Chinese and Caucasian adults at risk of T2DM were recruited to the study in which postprandial lipaemia and glycaemia were monitored following consumption of a high fat and high carbohydrate breakfast meal followed by a mixed, lunch meal. In a nonrandomised acute crossover trial, 15 adults (n = 8 Chinese and n = 7 Caucasian) aged ≥ 18 and ≤ 65 years at risk of T2DM (AUSDRISK score &gt; 12 (median = 14.0, IQR = 3.0)), attended two postprandial test days separated by ≥ 7-day washout period. Test breakfast meals were isocaloric (3.6 MJ), high fat (46% energy from fat, 46% energy from carbohydrates) or high carbohydrate (74% E carbohydrates, 17.5% E fat). Blood samples were collected at baseline (fasting), 180 min and 360 min after consumption of the breakfast meal. The lunch meal (3.7 MJ, 18% E fat, 76% E carbohydrates) was consumed 240 min after baseline. Samples were analysed for lipaemia and glycaemia. Additionally, chylomicron-rich, and VLDL-rich lipoprotein fractions were isolated by sequential ultracentrifugation and chylomicron particle number (apolipoprotein (apo) B48), triacylglycerol (TAG), and total cholesterol were assessed in these fractions. Data were analysed using a mixed between-within-subject analysis of variance. There were no differences in age, and baseline anthropometric measures between groups, apart from the Chinese group exhibiting significantly lower waist circumference and BMI compared to the Caucasian group. There were no differences between groups in blood measures, apart from a higher total- and LDL-cholesterol concentration in the Caucasian compared to the Chinese group (P&lt;0.05). Despite identical fasting TAG concentrations, the Chinese group, compared with the Caucasian group exhibited significantly elevated serum TAG and chylomicron-apo-B48 concentrations at 360 min following both test meals (P&lt;0.01). All other postprandial measures were not different between groups. These findings show that despite having identical or improved fasting glycaemia and lipid profile, the Chinese group exhibited impaired postprandial lipid metabolism which may contributes to their increased risk of metabolic diseases.

Quantifying Exhaled Particles in Healthy Humans During Various Respiratory Activities Under Realistic Conditions.

Background: Quantitatively collecting and characterizing exhaled aerosols is vital for infection risk assessment, but the entire droplet size spectrum has often been neglected. We analyzed particle number and size distribution of healthy participants in various respiratory activities, considering inter-individual variability, and deployed a simplified far-field model to inform on infection risks. Methods: Participants repeated the same respiratory activities on two visits. Particles were collected using an airtight extraction helmet supplied with High Efficiency Particulate Air (HEPA) filtered air. The sampling volume flow was transported to two particle counters covering the small and large particle spectrum. The applied simple mass balance model included respiratory activity, viral load, room size, and air exchange rates. Results: Thirty participants completed the study. The major fraction of the number-based size distribution was <5 μm in all respiratory activities. In contrast, the major fraction of the volume-based size distribution was 2-12 μm in tidal breathing, but >60 μm in all other activities. Aerosol volume flow was lowest in tidal breathing, 10-fold higher in quiet/normal speaking, deep breathing, coughing, and 100-fold higher in loud speaking/singing. Intra-individual reproducibility was high. Between participants, aerosol volume flow varied by two orders of magnitude in droplets <80 μm, and three orders of magnitude in droplets >80 μm. Simple model calculations not accounting for potential particle size-dependent differences in viral load and infection-related differences were used to model airborne pathogen concentrations. Conclusions: Quantitative analysis of exhaled aerosols for the entire droplet size spectrum as well as the variability in aerosol emission between individuals provides information that can support infection research. Clinical Trial Registration number: NCT04771585.

Relevance of plasma lipoproteins and small metabolites in assessment of nutritional status among patients with severe injuries

BackgroundThis study aimed to identify plasma lipoproteins and small metabolites associated with high risk of malnutrition during intensive care unit (ICU) stay in patients with severe injuries. MethodsThis observational prospective exploratory study was conducted at two level-1 trauma centers in the Netherlands. Adult patients (aged ≥18 years) who were admitted to the ICU for more than 48 h between July 2018 and April 2022 owing to severe injuries (polytrauma, as defined by Injury Severity Scores of ≥16) caused by blunt trauma were eligible for inclusion. Overall, 51 patients were included; partial least squares discriminant analysis was used to analyze the relationship of 112 lipoprotein-related components and 23 small metabolites with the risk of malnutrition (modified Nutrition Risk in Critically Ill score). Malnutrition was diagnosed based on Subjective Global Assessment scores. The relationship of lipoprotein properties and small metabolite concentrations with malnutrition (during ICU admission) was evaluated using mixed effects logistic regression. ResultsLower (very) low-density lipoprotein ([V]LDL) (free) cholesterol and phospholipid levels, low particle number, and higher levels of LDL triglycerides were associated with a higher risk of malnutrition (variable importance in projection [VIP] value >1.5). Low levels of most (V)LDL and intermediate-density lipoprotein subfractions and high levels of high-density lipoprotein Apo-A1 were associated with the diagnosis of malnutrition (VIP value >1.5). Increased levels of dimethyl sulfone, trimethylamine N-oxide, creatinine, N, N-dimethylglycine, and pyruvic acid and decreased levels of creatine, methionine, and acetoacetic acid were also indicative of malnutrition (VIP value >1.5). Overall, 14 lipoproteins and 1 small metabolite were significantly associated with a high risk of malnutrition during ICU admission (P <0.05); however, the association did not persist after correcting the false discovery rate (P=0.35 for all). ConclusionIncreased triglyceride in several lipoprotein subfractions and decreased levels of other lipoprotein subfraction lipids and several small metabolites (involved in the homocysteine cycle, ketone body formation, and muscle metabolism) may be indicative of malnutrition risk. Following validation in larger cohorts, these indicators may guide institution of preventive nutritional measures in patients admitted to the ICU with severe injuries.

Efficient simulation of stochastic interactions among representative Monte Carlo particles

Context. Interaction processes between discrete particles are often modelled with stochastic methods such as the Representative Particle Monte Carlo (RPMC) method which simulate mutual interactions (e.g. chemical reactions, collisions, gravitational stirring) only for a representative subset of n particles instead of all N particles in the system. However, in the traditionally employed computational scheme the memory requirements and the simulation runtime scale quadratically with the number of representative particles. Aims. We want to develop a computational scheme that has significantly lower memory requirements and computational costs than the traditional scheme, so that highly resolved simulations with stochastic processes such as the RPMC method become feasible. Results. In this paper we propose the bucketing scheme, a hybrid sampling scheme that groups similar particles together and combines rejection sampling with a coarsened variant of the traditional discrete inverse transform sampling. For a v-partite bucket grouping, the storage requirements scale with n and v2, and the computational cost per fixed time increment scales with n ⋅ v, both thus being much less sensitive to the number of representative particles n. Extensive performance testing demonstrates the higher efficiency and the favourable scaling characteristics of the bucketing scheme compared to the traditional approach, while being statistically equivalent and not introducing any new requirements or approximations. With this improvement, the RPMC method can be efficiently applied not only with very high resolution but also in scenarios where the number of representative particles increases over time, and the simulation of high-frequency interactions (such as gravitational stirring) as a Monte Carlo process becomes viable.

Measurement and Analysis of Brake and Tyre Particle Emissions from Automotive Series Components for High-Load Driving Tests on a Wheel and Suspension Test Bed

A current challenge in realising clean road transport is non-exhaust emissions. Important advances regarding measurement systems, including well-defined characterisation techniques, as well as regulation, will be made in the next few years. In this work, we present the detailed results of particle emission analyses, consisting of aerosol (size distribution, particle number (PN), and mass (PM)) and electron microscopy (EM) measurements, under different load conditions on a test bed for a wheel suspension and brakes. Standard tyres and brakes from serial production were tested with a high-load driving cycle, while particle measurements were conducted by gravimetric measurements and with a TSI SMPS, a TSI APS, and a GRIMM OPS. Furthermore, samples were analysed by electron microscopy. A bimodal particle size distribution (PSD) was obtained with an SMPS, with peaks at 20 nm and around 400 nm. The results of an EM analysis of &gt;1400 single particles from the electrostatic sampler match the PSD results. The EM analysis also showed ultrafine particles, mainly containing O, Fe, Si, Ba, Mg, and S, and also fractal particles with high-C fractions. Our results suggest, in agreement with the previously published literature, that particulate emissions are related to the brake disc temperature and occur in significant amounts above a threshold temperature.

Commercial plant protein isolates: The effect of insoluble particles on gelation properties

Commercial plant protein isolates generally contain a substantial fraction of large insoluble protein particles. We study how these affect the gelation properties of heat-induced protein gels (15% w/w protein, pH 7) and used homogenization as a mean to reduce the particle size of the insoluble fraction before gelation. Three different commercial plant proteins were studied as models for isolates differing in dispersibility and size of insoluble protein particles: Fava bean (FBPI), Pea (PPI) and Mung bean (MBPI). As expected, homogenization (50 MPa, 2 cycles) reduced the particle size and improved the dry matter dispersibility of protein dispersions. We found that the (shear) storage modulus G’ and critical shear strain for fracture of gels obtained after heating were not consistently impacted by homogenization. In contrast, fracture properties in uniaxial compression were sensitive to homogenization, with homogenization leading to gels that are more resistant to fracture. Gels obtained from the isolate with the smallest fraction of insoluble particles and still contained native proteins, FBPI, were the most fracture resistant. Fluorescence microscopy indicated that the insoluble fraction remained well-dispersed in the matrix after heat-induced gelation and that homogenization led to a more homogeneous appearance of the protein networks, with smaller particles being homogeneously dispersed in the continuous background. We conclude that mechanically breaking down insoluble particles in commercial plant protein isolates contributes strongly to their functionality by reducing the number of large insoluble particles that act as effective nucleation points for hydrogel fracture.

Investigation of the influence mechanism of hypersonic flow field environment on thermionic emission efficiency

Electron Transpiration Cooling (ETC) is a novel thermal management method that utilizes thermionic emission to cool the leading edge surface of a hypersonic vehicle. Establishing a thermionic emission model that accounts for the hypersonic flow field environment is imperative for accurately predicting the thermal protection efficiency of ETC. A thermionic emission dual-sheath model was established, considering the impact of hypersonic non-equilibrium flow field particle parameters on thermal electron emission. The virtual cathode threshold was obtained through numerical analysis, considering the influence of particles parameters and surface thermoelectric material parameters in a non-equilibrium flow field. Distribution of sheath potential and particle number density in plasma sheath region were performed at a range of conditions. Thermionic emission efficiency approached 80 % as the plasma ion density was 5 × 20 m−3 and the work function was 2 eV. The results showed that plasma ions have different degrees of neutralization effect on thermal emission electrons depending on the flow field and surface material characteristics, ultimately causing varying surface thermionic emission efficiency.

Characteristics of number concentration, size distribution and components of particulate matter emitted from a typical large civil airport

Civil airports are recognized as significant contributors to fine particulate matter, especially ultra-fine particulate matter (UFP). The pollutants from airport activities have a notable adverse impact on global climate, urban air quality, and public health. However, there is a lack of practical observational studies on the characterization of integrated pollutant emissions from large civil airports. This study aims to focus on the combined emission characteristics of particulate number concentration (PNC), size distribution, and components at a large civil airport, especially UFP. The findings reveal that airport activities significantly contribute to elevated PNC levels during aircraft activity in downwind conditions (four times higher than background levels) and upwind conditions (7.5 times higher). UFP dominates the PNC around the airport. The particle size distribution shows two peaks occurring around 10-30 nm and 60-80 nm. Notably, particles within the ranges of 17-29 nm and 57-101 nm account for 65.9 % and 12.0 % of the total PNC respectively. Aircraft landing has the greatest impact on particles sized between 6 and 17 nm while takeoff affects particles sized between 29 and 57 nm resulting in a respective increase in PNC by factors of approximately 3.27 and 35.4-fold increase compared to background levels. Different aircraft types exhibit varying effects on PNC with A320 and A321 showing more pronounced effects during takeoff and landing.The presence of airports leads to roughly five-fold rise in elemental component concentrations with Si being highest followed by OC, Ca, Al, Fe, Ca2+, EC, and Mg2+. The OC/EC ratio under high aircraft activity in downwind conditions falls within range of approximately 2.5–3.5. These characteristic components and ratio can be considered as identifying species for civil airports. PMF model show about 75 % of the particulate emissions at the airport boundary were related to airport activities.

Chaos and anomalous transport in a semiclassical Bose-Hubbard chain.

We study chaotic dynamics and anomalous transport in a Bose-Hubbard chain in the semiclassical regime (the limit when the number of particles goes to infinity). We find that the system has mixed phase space with both regular and chaotic dynamics, even for long chains with up to 100 wells. The consequence of the mixed phase space is strongly anomalous diffusion in the space of occupation numbers, with a discrete set of transport exponents. After very long times the system crosses over to the hydrodynamic regime with normal diffusion. Anomalous transport is quite universal and almost completely independent of the parameters of the model (Coulomb interaction and chemical potential): It is mainly determined by the initial distribution of particles along the chain. We corroborate our findings by analytical arguments: scaling analysis for the anomalous regime and the Langevin equationfor the normal diffusion regime.

Towards a reference material for microplastics’ number concentration—case study of PET in water using Raman microspectroscopy

Increasing demand for size-resolved identification and quantification of microplastic particles in drinking water and environmental samples requires the adequate validation of methods and techniques that can be used for this purpose. In turn, the feasibility of such validation depends on the existence of suitable certified reference materials (CRM). A new candidate reference material (RM), consisting of polyethylene terephthalate (PET) particles and a water matrix, has been developed. Here, we examine its suitability with respect to a homogeneous and stable microplastic particle number concentration across its individual units. A measurement series employing tailor-made software for automated counting and analysis of particles (TUM-ParticleTyper 2) coupled with Raman microspectroscopy showed evidence of the candidate RM homogeneity with a relative standard deviation of 12% of PET particle counts involving particle sizes >30 µm. Both the total particle count and the respective sums within distinct size classes were comparable in all selected candidate RM units. We demonstrate the feasibility of production of a reference material that is sufficiently homogeneous and stable with respect to the particle number concentration.Graphical

Evaluation of the point sampling method and inter-comparison of remote emission sensing systems for screening real-world car emissions

Emissions from internal combustion vehicles are currently not properly monitored throughout their life cycle. Remote emission sensing (RES) is a technology that can measure emissions under real driving conditions without contact. Current light extinction based RES systems are capable of providing emission factors for various gases, but lack accuracy for particulate matter (PM). Point Sampling (PS) is an extraction-based RES technique that can measure gases as well as various particle metrics such as black carbon or particle number. In this work, we evaluated the performance of a recently developed PS system and the state-of-the-art light extinction based remote sensing devices EDAR (HEAT) and ORSD (OPUS RSE) during co-location measurements. Validation measurements with portable emission measurement systems and emissions screening of several thousand cars in three European cities provide detailed insights into system's performance. Meteorological evaluations showed that the PS capture rate is strongly influenced by wind, but no other weather influences were found. Both light extinction based systems are unable to measure during rain. We found that all three systems tested were capable of screening NOx emissions from pre-Euro 6 diesel cars. Measurement results show the ability of the PS system to quantify high and low PM emitters equally well. The open-path RES systems (EDAR, ORSD) are capable of estimating PM emissions from pre-Euro 5 diesel cars. However, deficiencies of open-path RES systems are evident in the quantification of PM emissions from newer engine technologies (diesel Euro 5 and beyond) and from petrol cars. The PS system has a 2 to 5 times lower capture rate than open-path RES systems, but the PS measurement results are more accurate (more than 5 times for PM and more than 1.35 times for NOx). The good accuracy of individual measurements makes PS a powerful tool for reliable high emitter identification.