Increase In Number Of Particles Research Articles

Research on jet ignition phases and control parameters in an active pre-chamber optical engine under ultra-lean combustion conditions

The active pre-chamber (APC) jet ignition system is one of the primary technologies for achieving ultra-lean combustion and high thermal efficiency in engines. The impact of the jet process within the engine, as well as its control parameters, on emission pollutants (particularly soot particles) remains unclear. This study focuses on examining the effects of various low-flow injection control strategies on engine combustion and emissions by using optical experiments and numerical simulations. It also explores the impact of different ignition advance angles (ignition timings) based on a short pre-chamber mixing interval to observe ignition combustion, flame propagation, and emission characteristics under ultra-lean conditions (λ = 2.0). The main conclusions are as follows. Appropriately increasing the injection mass can enhance engine load. However, further increases in injection mass significantly raise particulate emissions, resulting in an increase in particle number by up to more than 37-fold, especially for small particles in the 5–––10 nm size range. The chemical reaction between the luminous jet flame and the bright incandescent wake jet flame, as captured by high-speed photography, effectively characterizes the various stages of jet ignition. To reduce particulate matter emissions, it is crucial to avoid the foreseeable wake jet flame caused by the enrichment of the jet mixture in the pre-chamber. The low-flow injection timing should neither be too early nor close to the ignition spark timing. The early injection causes fuel to accumulate at the top of the pre-chamber, hindering the jet flame’s propagation into the main combustion chamber. Late low-flow injection leads to fuel enrichment, resulting in uneven mixing and poor atomization and diffusion due to short mixing times. Ignition after a short mixing time interval tends to increase knocking, resulting in intense combustion and an advanced phase, which slightly reduces load and combustion stability. Regarding the heat release ratio, the total heat release from the two combustion stages in the pre-chamber should ideally account for about 5–6 % of the heat release in the main chamber.

Comparison of aerosol number size distribution and new particle formation in summer at alpine and urban regions in the Guanzhong Plain, Northwest China

Ultrafine particles play a crucial role in understanding climate change, mitigating adverse health effects, and developing strategies for air pollution control. However, the factors influencing the occurrence and development of new particle formation (NPF) events, as well as the underlying chemical mechanisms, remain inadequately explained. This study compared number concentrations and size distributions of atmospheric ultrafine particles at Xi'an (urban area) and the summit of Mt. Hua (alpine region) in summer to investigate the NPF mechanism and particle growth in both clean and polluted areas of the Guanzhong Plain. The average particle number concentration in Xi'an was significantly higher than that at Mt. Hua. The diurnal variation of total particle number concentration differed between Xi'an and Mt. Hua indicating a divergence in influencing factors. The size distributions in Xi'an varied across different timescales and weather conditions, whereas Mt. Hua exhibited little variation. This stability at Mt. Hua is attributed to its cleaner background atmosphere and the steady influx of aging particles with larger diameters transported from the free atmosphere. In both areas, geometric mean diameters (GMDs) were inversely proportional to particle number concentrations suggesting that increase in particle numbers were primarily due to the generation of smaller particles. The potential governing factors for NPF events differed somewhat between the urban and mountainous stations. In the urban area, intense local stationary and mobile emission sources promoted the growth of newly formed nanoparticles, with ozone-oxidized condensable vapors serving as key precursors. In contrast, at the mountainous station, NPF process were significantly influenced by anthropogenic precursors from long-range transport and locally emitted biogenic organics. The rapid increase in ultrafine particle concentrations primarily poses serious health risks and degrades air quality in urban areas, while also contributing to climate-related effects in alpine regions.

Role of bolus properties in dynamic texture perception of meat analogue and beef patties: Juiciness is driven by serum release during early stages of mastication

The sensory quality of plant-based meat analogues (PBMAs) limits wider consumer acceptance, particularly because of their lack of perceived juiciness. This study aimed to investigate the role of bolus properties at different moments of consumption in dynamic texture perception, especially juiciness, of PBMA and beef patties. Patties were cooked to three core temperatures (60, 70, 80 °C) to obtain specimens differing in juiciness. For PBMA and beef patties, juiciness citation proportions (Temporal-Check-All-That-Apply) peaked within the first third of mastication, then decreased strongly until swallowing. This temporal pattern closely aligned with the serum release during mastication as 75% of serum was released from patties during the first third of mastication. Additional structural breakdown of bolus occurred until the end of mastication accompanied by less than 25% additional serum release. With increasing mastication, PBMA and beef patties showed a significant increase in saliva uptake and number of bolus particles, while bolus particle size and hardness decreased, demonstrating a progressive oral structural breakdown. No significant differences in bolus properties were observed between PBMA patties differing in juiciness, while beef patties varying in juiciness differed significantly in bolus water content and liquid expelled from bolus, as a result of the structural changes of myofibrillar protein upon heating. We conclude that, for the patties used in this study, juiciness perception of PBMA patties is driven by serum release during early stages of mastication and not effected by additional oral structural breakdown, while juiciness of beef patties is affected by initial serum release and differences in bolus properties resulting from additional oral structural breakdown.

Enterocyte-specific FATP4 deficiency elevates blood lipids via a shift from polar to neutral lipids in distal intestine.

Fatty acid transport protein (FATP)4 was thought to mediate intestinal lipid absorption, which was disputed by a study using keratinocyte-Fatp4-rescued Fatp4-/- mice. These knockouts when fed with a Western diet showed elevated intestinal triglyceride (TG) and fatty acid levels. To investigate a possible role of FATP4 on intestinal lipid processing, ent-Fatp4 (KO) mice were generated by Villin-Cre-specific inactivation of the Fatp4 gene. We aimed to measure circulating and intestinal lipids in control and KO mice after acute or chronic fat intake or during aging. Remarkably, ent-Fatp4 mice displayed an approximately 30% decrease in ileal behenic, lignoceric, and nervonic acids, ceramides containing these FA, as well as, ileal sphingomyelin, phosphatidylcholine, and phosphatidylinositol levels. Such decreases were concomitant with an increase in jejunal cholesterol ester. After a 2-wk recovery from high lipid overload by tyloxapol and oral-lipid treatment, ent-Fatp4 mice showed an increase in plasma TG and chylomicrons. Upon overnight fasting followed by an oral fat meal, ent-Fatp4 mice showed an increase in plasma TG-rich lipoproteins and the particle number of chylomicrons and very low-density lipoproteins. During aging or after feeding with a high-fat high-cholesterol (HFHC) diet, ent-Fatp4 mice showed an increase in plasma TG, fatty acids, glycerol, and lipoproteins as well as intestinal lipids. HFHC-fed KO mice displayed an increase in body weight, the number of lipid droplets with larger sizes in the ileum, concomitant with a decrease in ileal ceramides and phosphatidylcholine. Thus, enterocyte FATP4 deficiency led to a metabolic shift from polar to neutral lipids in distal intestine rendering an increase in plasma lipids and lipoproteins.NEW & NOTEWORTHY Enterocyte-specific Fatp4 deficiency in mice increased intestinal lipid absorption with elevation of blood lipids during fasting and aging, as well as after an acute oral fat-loading or chronic HFHC feeding. Lipidomics revealed that knockout mice displayed a shift from very long-chain to long-chain fatty acids, and from polar to neutral lipids, predominantly in the ileum. Thus, FATP4 may have a physiological function in the control of blood lipids via metabolic shifts in distal intestine.

Impact of RA treatment strategies on lipids and vascular inflammation in rheumatoid arthritis: a secondary analysis of the TARGET randomized active comparator trial

BackgroundTreatments for rheumatoid arthritis (RA) are associated with complex changes in lipids and lipoproteins that may impact cardiovascular (CV) risk. The objective of this study was to examine lipid and lipoprotein changes associated with two common RA treatment strategies, triple therapy or tumor necrosis factor inhibitor (TNFi), and association with CV risk.MethodsIn this secondary data analysis of the TARGET trial, methotrexate (MTX) inadequate responders with RA were randomized to either add sulfasalazine and hydroxychloroquine (triple therapy), or TNFi for 24-weeks. The primary trial outcome was the change in arterial inflammation measured in the carotid arteries or aorta by FDG-PET/CT at baseline and 24-weeks; this change was described as the target-to-background ratio (TBR) in the most diseased segment (MDS). Routine lipids and advanced lipoproteins were measured at baseline and 24-weeks; subjects on statin therapy at baseline were excluded. Comparisons between baseline and follow-up lipid measurements were performed within and across treatment arms, as well as change in lipids and change in MDS-TBR.ResultsWe studied 122 participants, 61 in each treatment arm, with median age 57 years, 76% female, and 1.5 year median RA disease duration. When comparing treatment arms, triple therapy had on average a larger reduction in triglycerides (15.9 mg/dL, p = 0.01), total cholesterol to HDL-C ratio (0.29, p-value = 0.01), and LDL particle number (111.2, p = 0.02) compared to TNFi. TNFi had on average a larger increase in HDL particle number (1.6umol/L, p = 0.006). We observed no correlation between change in lipid measurements and change in MDS-TBR within and across treatment arms.ConclusionsBoth treatment strategies were associated with improved lipid profiles via changes in different lipids and lipoproteins. These effects had no correlation with change in CV risk as measured by vascular inflammation by FDG-PET/CT.Trial registrationClinicalTrials.gov ID NCT02374021.

Shear flow dynamics in vibrated granular materials: Analysis of viscosity transitions and non-Newtonian behaviors

In a continuous fluid, the presence of a velocity gradient perpendicular to the flow creates shear stress and shear rate between adjacent layers. The fluid's viscosity can be constant, depending only on temperature (Newtonian fluid), or vary with shear rate (non-Newtonian fluid). However, the viscosity characteristics of shear flows in discrete media, such as vibrated granular materials, remain insufficiently understood. This study experimentally investigated shear flows in vibrated granular media, exploring the relationship between shear stress, shear rate, and the impact of vibration conditions and particle number on granular viscosity. The findings indicate that the viscosity of sheared granular material transitions between dilatant and pseudoplastic non-Newtonian states with increasing vibration strength, shifts from pseudoplastic non-Newtonian fluid to Newtonian fluid with increasing vibration frequency, and remains consistently pseudoplastic non-Newtonian with increasing particle number. Two continuous non-Newtonian fluid models were utilized for comparison with our experimental results. Additionally, ascending curves of granular viscosity against granular temperature reveal gas-like flow characteristics in the sheared granular material, albeit with an abnormal descending viscosity–temperature relationship. These are attributed to volume expansion and oblique collisions in the vibrated granular medium. This study uncovers distinct viscosity properties in a discrete medium under shear flows, markedly different from those in continuous fluids, and highlights potential new applications for granular materials.

Breakdown of Temporal Coherence in Photon Condensates.

The temporal coherence of an ideal Bose gas increases as the system approaches the Bose-Einstein condensation threshold from below, with coherence time diverging at the critical point. However, counterexamples have been observed for condensates of photons formed in an externally pumped, dye-filled microcavity, wherein the coherence time decreases rapidly for increasing particle number above threshold. This Letter establishes intermode correlations as the central explanation for the experimentally observed dramatic decrease in the coherence time beyond critical pump power.

Iron oxide nanoparticle synthesis: Simulation-based comparison of laboratory- and pilot plant-scale spray-flame synthesis

This study analyzes burner scale-dependent effects for iron-oxide nanoparticles synthesis in spray flames through a combined experimental and numerical approach. A laboratory- and a pilot plant-scale synthesis facility generate iron oxide nanoparticles from iron nitrate dissolved in ethanol/2-ethylhexanoic acid solvents on the 0.5 and 15 g/h scale, respectively. Phase Doppler measurements supply initial conditions for spray development in the numerical approach, while in situ OH* chemiluminescence and multi-line nitric oxide laser-induced fluorescence (NO-LIF) thermometry provide experimental data for comparison with simulation results of the pilot plant burner. Ex situ particle sizing by gas adsorption according to Brunauer-Emmet-Teller (BET) and transmission electron microscopy (TEM), along with phase composition determination via X-ray diffraction (XRD), are used to compare products of both burners and the corresponding simulations. The numerical approach employs a Reynolds-averaged Eulerian–Lagrangian description of the flow in combination with a flamelet/progress variable (FPV) combustion and monodisperse particle model to reflect spray-flame synthesis. Despite similar chemiluminescence between experiment and simulation, more significant discrepancies are observed in NO-LIF thermometry and particle sizing. Nanoparticle formation and growth at both burner scales is investigated using the numerical method. Special attention is directed to the high-temperature particle residence time (HTPRT). Notably, the average temperature–time profiles particles experience are almost identical in the burners, although their geometric scales and designs differ substantially. Simulation results show that while the primary particle diameter remains mostly consistent, the pilot-scale burner produces larger particle agglomerates than the laboratory burner. The difference is attributed to an increased particle number concentration during the initial formation of soft agglomerates. The findings demonstrate that, despite retaining a similar HTPRT, the overall flow conditions and liquid spray dispersion, which impact the distribution of the particle number concentration, influence the final agglomerate size.

Particulate matter emissions from light-duty gasoline vehicles under different ambient temperatures: Physical properties and chemical compositions

Fine particulate matter (PM2.5) from vehicle exhaust is typically emitted at breathing height and thus imposes severe adverse effects on human health and air quality. However, there is currently limited knowledge on the characteristics of PM2.5 in exhaust, specifically its chemical components, at different ambient temperatures. Particulate emissions from typical light-duty gasoline vehicles (LDGVs) were investigated on a chassis dynamometer according to the Worldwide Harmonized Light-Duty Test Cycle at ambient temperatures of 38 °C, 28 °C, 15 °C, 5 °C and − 7 °C. The results showed a significant increase in particulate mass (PM) and particle number (PN) emissions with decreasing ambient temperature, particularly during cold starts below 5 °C. The particle size distributions exhibited distinct bimodal patterns, with accumulation-mode (AM) particles (60–125 nm) dominating the gasoline direct injection (GDI) distribution and nucleation-mode (NM) particles (8–12 nm) dominating the port fuel injection (PFI) distribution. AM particles were more temperature-sensitive than NM particles. Lower temperatures produced higher emissions of elements, carbonaceous components, and large-ring polycyclic aromatic hydrocarbons, while water-soluble ions showed an opposite trend. The total toxic equivalent, primarily influenced by benzo[a]pyrene, was significantly higher at −7 °C. The penalty distribution of LDGV PM and PN, defined by comparing the emissions at the various temperatures to those at regulated temperatures (23–30 °C), exhibited notable temporal heterogeneity (winter > autumn > spring > summer) and spatial heterogeneity (northern China > southern China). These findings are essential for establishing more stringent vehicle emission standards and improving emission models in cold environments.

Lipoprotein(a) Is Markedly More Atherogenic Than LDL: An Apolipoprotein B-Based Genetic Analysis

BackgroundLipoprotein(a) (Lp(a)) is recognized as a causal factor for coronary heart disease (CHD) but its atherogenicity relative to that of low-density lipoprotein (LDL) on a per-particle basis is indeterminate. ObjectivesThe authors addressed this issue in a genetic analysis based on the fact that Lp(a) and LDL both contain 1 apolipoprotein B (apoB) per particle. MethodsGenome-wide association studies using the UK Biobank population identified 2 clusters of single nucleotide polymorphisms: one comprising 107 variants linked to Lp(a) mass concentration, the other with 143 variants linked to LDL concentration. In these Lp(a) and LDL clusters, the relationship of genetically predicted variation in apoB with CHD risk was assessed. ResultsThe Mendelian randomization-derived OR for CHD for a 50 nmol/L higher Lp(a)-apoB was 1.28 (95% CI: 1.24-1.33) compared with 1.04 (95% CI: 1.03-1.05) for the same increment in LDL-apoB. Likewise, use of polygenic scores to rank subjects according to difference in Lp(a)-apoB vs difference in LDL-apoB revealed a greater HR for CHD per 50 nmol/L apoB for the Lp(a) cluster (1.47; 95% CI: 1.36-1.58) compared with the LDL cluster (1.04; 95% CI: 1.02-1.05). From these data, we estimate that the atherogenicity of Lp(a) is approximately 6-fold (point estimate of 6.6; 95% CI: 5.1-8.8) greater than that of LDL on a per-particle basis. ConclusionsWe conclude that the atherogenicity of Lp(a) (CHD risk quotient per unit increase in particle number) is substantially greater than that of LDL. Therefore, Lp(a) represents a key target for drug-based intervention in a significant proportion of the at-risk population.

Femtosecond Laser Preparation and Biomineralizability of ZrO2 Ceramic Woven Surfaces

Improving the biomineralization of the ZrO2 ceramics surface is of great significance for field of dentistry. A femtosecond laser is used to prepare micro–nano structures on the surface of the ZrO2 ceramics. The contact angle, micromorphology, and chemical composition of the material surface are characterized using a contact angle measurement instrument, scanning electron microscope, and energy‐dispersive spectroscopy. The changes of surface wettability of different samples areanalyzed, and the biomineralization of different micropit surfaces is evaluated through hydroxyapatite (HA) deposition experiments. The results show that the deposition effect of the femtosecond laser‐textured surface is better than that of the original surface. Femtosecond laser processing improves the surface of the material, providing additional nucleation sites for HA, which is conducive to its growth and improvement of deposition efficiency. HA deposited on hydrophobic surfaces consists of a small amount of rod‐shaped and spherical particles. While the deposition effect on hydrophilic surfaces is significantly improved, the deposited particles on hydrophilic surfaces are rod‐shaped and stacked into spherical shapes, growing into pieces after combining, and the particle number increases, the density increases, and they completely cover the textured surface. This study provides a theoretical reference and experimental basis for improving its biomineralization.

Classification of pairing phase transition in the hot nucleus

The hot nucleus [Formula: see text] is investigated using covariant density functional theory, where the shell-model-like approach treats the pairing correlation. Lee–Yang’s theorem is applied to classify the pairing phase transition by analyzing the distribution of zeros of the partition function in the complex temperature plane. The distribution of zeros of the partition function converges with increasing particle numbers and illustrates the characteristics of the phase transition. In our calculations, we determine the first-order of the phase transition near the critical temperature. Different seniority states show the pairing phase transition from a superfluid to a normal phase, ranging from fully paired states to completely unpaired states.

Investigating the Particle Formation Mechanism during Precipitation of Ni-Rich Hydroxide Precursors for Cathode Active Materials for Lithium-Ion Batteries

The industrial production of lithium-nickel-cobalt-manganese-oxides (LiNi x Co y Mn z O2, with x+y+z = 1) as cathode active material (CAM) for lithium-ion batteries is conducted by precipitation of a mixed metal hydroxide (Ni x Co y Mn z (OH)2) precursor (referred to as pCAM) in a stirred tank reactor, followed by a calcination of the pCAM with a lithium compound at elevated temperatures in a roller hearth kiln.1 Thereby, the physical properties of the resulting CAM powders are significantly affected by those of the associated pCAM.2 Independent of the material composition, the fluidity and filterability of pCAM and CAM powders deteriorates drastically with decreasing particle size, with non-uniformity of the particle size distribution, and with a deviation from a spherical particle shape.3,4 However, a fluent form of the pCAM and CAM powders is imperative for their further processing in tonnage quantities during pCAM and CAM manufacturing to prevent clogging of the powders in the technical equipment. As frequent cleaning and/or pulverization of the materials between process steps is cost-intensive, an economical and efficient manufacturing of pCAM and CAM powders requires a precise control of particle size and sphericity, which in turn requires an in-depth knowledge of the pCAM particle formation mechanism during the precipitation reaction.To gain a fundamental mechanistic understanding about the pCAM particle formation mechanism, the development of the secondary particle size and morphology during the semi-batch precipitation of Ni0.8Co0.1Mn0.1(OH)2 at various stirring speeds (between 550 and 1350 rpm) was monitored by light scattering and SEM imaging. The evolution of the volume-based median particle size (d 50) over the course of the run time (t run) at the different stirring speeds is depicted in Figure 1a. The d 50 of initial particles generated after 5 minutes as well as the d 50 after 8.75 h depends inversely on the applied stirring speed. After an initial nucleation time, the analysis in Figure 1b shows that the size of the approximatively spherical particles at a given stirring speed (for constant feed flow rates) increases linearly with respect to the third square root of run time/run time to the power of one third (t run1/3 ). Thus, the course of particle growth in each experiment can be divided into two distinct regimes: i) for t run1/3 < 1.0 (stage I in Figure 1b), the particle size remains essentially constant; ii) after this initial phase, for t run1/3 ≥ 1.0 (stage II in Figure 1b), the d 50 increases perfectly linearly with. It is concluded that during stage I, the seeding phase, an increasing number of particles with a constant size are being generated, since the overall volume of formed solid is increasing. In contrast, in stage II, the growth phase, the continuing precipitation occurs via deposition on already existing particles without any further increase in particle number, reflected by the linear relationship between particle size and t run1/3 .In light of these results, it is further demonstrated by SEM imaging that, during the seeding phase (stage I), irregularly shaped secondary particle agglomerates are formed, which in the subsequent growth phase (stage II) increase in size by growth of individual plate-like shaped primary particles. Moreover, it is shown that, at constant process parameters, the degree of turbulence quantified by the average energy input and the Reynolds number, both depending on the stirring speed, governs the initial agglomerate size formed during seeding. This not only dictates the growth rate, thus the final particle size, but also the ability of particles to become spherical over t run. Finally, a particle formation mechanism is proposed and compared to mechanisms described in the literature. Figure 1

Numerical analysis of catalyst particle deposition characteristics in a flue gas turbine with an improved particle motion and deposition model

To more accurately understand and predict the deposition behavior of catalyst particles in the flue gas turbine cascade, test and numerical combined study is performed in this paper. Based on the systematic analysis of the deposition process and physical mechanism of the catalyst particles, the traditional DRW model, critical velocity particle deposition model and removal model were corrected with the user defined function custom function and validated with the actual deposition morphology. On this basis, the effects of the particle Stokes number and flue gas parameters on the particle deposition characteristics of the flue gas turbine cascade were detailed investigated. The results show that the revised DRW model, critical velocity and removal model can more accurately predict the deposition location and deposition rate of particles in the turbine cascade. With the increase in the Stokes number of particles, the average particle impact rate on the blade surface gradually increased, while the average deposition rate showed a trend of first increasing and then decreasing. The average deposition rate of particles in the rotor blade surface is roughly twice as high as that in the stator surface. With the increase of the flue gas expansion ratio, the deposition rate of particles less than 3 μm gradually increases, while the deposition rate of particles greater than 3 μm tends to decrease. In addition, the change in the flue gas expansion ratio has no obvious effect on the particle deposition distribution in different size ranges.

The benefits of measuring the size and number of lipoprotein particles for cardiovascular risk prediction: A systematic review and meta-analysis

ObjectiveCardiovascular risk (CVR) is conventionally calculated by measuring the total cholesterol content of high-density lipoproteins (HDL) and low-density lipoproteins (LDL). The purpose of this systematic review was to assess the CVR associated with LDL and HDL particle size and number as determined by nuclear magnetic resonance (NMR) spectroscopy. Material and methodsA literature search was performed using the electronic databases MEDLINE and Scopus. All cohort and case–control studies published before January 1, 2019 that met the following inclusion criteria were included: HDL-P, LDL-P, HDL-Z and/or LDL-Z measured by NMR spectroscopy; cardiovascular event as an outcome variable; risk of cardiovascular events expressed as odds ratios or hazard ratios; only adult patients. A meta-analysis was performed for each exposure variable (4 for LDL and 5 for HDL) and for each exposure measure (highest versus lowest quartile and 1-standard deviation increment). ResultsThis review included 24 studies. Number of LDL particles was directly associated with CVR: risk increased by 28% with each standard deviation increment. LDL particle size was inversely and significantly associated with CVR: each standard deviation increment corresponded to an 8% risk reduction. CVR increased by 12% with each standard deviation increase in number of small LDL particles. HD, particle number and size were inversely associated with CVR. ConclusionLarger particle size provided greater protection, although this relationship was inconsistent between studies. Larger number of LDL particles and smaller LDL particle size are associated with increased CVR. Risk decreases with increasing number and size of HDL particles.

Instabilities in Random Media and Peaking Regimes

We consider a system of particles (bacteria) in a medium, in which the birth and death intensities are distributed in space at random. In this system, we study the increase in the average number of particles, which depends on the difference between the birth intensity and the death intensity and is referred to as the random potential. It is shown that if the potential decreases quite slowly at infinity, the explosive growth in the number of bacteria and their average population formally turns to infinity immediately after the beginning of system evolution. In addition, it is shown that the finiteness of the average numbers of bacteria for each specific realization of the medium does not guarantee the finiteness of the average numbers of bacteria in the averaging over all realizations of the medium. Finally, we describe the behavior of the average numbers of bacteria averaged over the medium for a wide class of potentials for long times.

A GPU based Hybrid Material point and Discrete element method (MPDEM) algorithm and validation

The interaction between granular material and rigid bodies or complex boundaries are common in geotechnical engineering and industry. A hybrid MPDEM algorithm is proposed to simulate these kinds of problems. It is combined with the ability for solving granular material in MPM and the advantages of contact detection in DEM, which can be applied to solve sliding and impacting behavior of rigid blocks. Furthermore, the coupling algorithm based on GPU can be adopted for large-scale simulation to improve the calculation efficiency which has powerful advantages in geologic hazards simulation with high efficiency. To validate the algorithm, the sliding friction and impact effects are conducted to check the contact detection and force calculation for interaction between granular and block or boundary. Besides, the simulation results of granular impacting on the blocks are in good agreement with the experiment, which represents the feasibility and ability of algorithm to solve the interaction with granular materials and rigid-blocks or boundary systems. Through efficiency analysis, it is concluded that the computational performance is higher with the increase in particle number, compared with the pure MPM contact method. Additionally, the Tesla V100 card is a better choice for large-scale (particle number more than 1 million) simulations.

Assessment of fine droplets (

Passive samplers are especially inefficient when collecting and measuring the finest particles in primary airborne spray drift far from the spray source. We describe a method to improve the measurement of <10 μm-sized droplets that become airborne during crop spray applications. An airblast sprayer was combined with Conventional (VMD 90 μm) and Low Drift (VMD 276 μm) nozzles. Downwind droplet concentrations were measured at six sampling distances (5, 10, 15, 20, 25, and 30 m) from the sprayer pathway using an Optical Particle Counter (OPC). The instrument simultaneously measures particle mass (μg m−3) and particle number (n). Three particle size ranges were considered (<1.0, 1.0–2.5, and 2.5–10.0 μm). Weather conditions were monitored to ensure optimal spray drift generation as dictated by the ISO22866:2005 which allowed comparison of the two nozzle technologies. Significant downwind particle mass and number increases were observed using proposed methodology compared to the background level with either Conventional or Low Drift nozzles. As expected, more massive fine droplets (+55%) resulted with Conventional nozzles. Interestingly, the Low Drift nozzles highlighted their potential to generate more fine particles (<1.0 μm) at 25 and 30 m from the sprayer. This study verified the potential to use OPCs to assess drift and understand particle size variation and dynamics during drift events.

Molecular dynamics simulation of thermal conductivity of diamond/epoxy resin composites

Improving the thermal conductivity (TC) of epoxy resin thermal interface material is of great significance in tackling the heat dissipation problem of high heat flux in microelectronic chips such as 5G. Using non-equilibrium molecular dynamics (MD) method, the effects of two different filling styles of nano-diamond fillers on the TC of EP based composites are investigated. The results show that the TC of the composite increases with the diamond size when single-particle filling is used, and that a larger diamond size leads to a more significant reduction of the free volume fraction and thus an improvement of the TC. In the multi-particle packing, the composite TC first increases and then decreases with increasing particle number. Increasing the number of particles reduces the free volume fraction, but also results in a larger specific surface area and interfacial thermal resistance, which has a more significant weakening effect on the TC. Moreover, within the same mass fraction of nano-diamond filler, increasing the filler size has a more significant TC improvement on the composite than increasing the number of particles. This study is instructive for the design and preparation of high thermal conductivity nanodiamond/epoxy resin composites.

Deep Learning Aided State Estimation for Guarded Semi-Markov Switching Systems With Soft Constraints

This paper investigates the problem of state estimation for guarded semi-Markov switching systems with soft constraints. We first construct the switching system in a multiple model manner and derive the recursive Bayesian filter compatible with the sojourn time and base state dependent mode transitions. To solve the intractable conditioned mode transition probabilities, we develop deep learning based classifiers with long short-term memory networks capturing the temporal dependencies. Various network structures are designed to handle different situations where knowledge of the transition probability matrix is available or deficient. Furthermore, we incorporate sequential Monte Carlo techniques into the multiple model framework to resolve the local filtering task. A novel particle refinement procedure exploiting the constraint information is proposed to improve the efficiency of particle propagation and prevent the exponential increase of particle number simultaneously. Simulations on a robotic manipulator and an autonomous vehicle tracking task validate the effectiveness of the proposed state estimation method.