Escape Rate Research Articles

Optimization of combustion chamber geometry for a two-stroke spark-ignited direct-injection opposed-piston rod-less aviation kerosene engine

Spark-ignited direct-injection opposed-piston rod-less kerosene engines are highly suitable for small and medium-size unmanned aerial vehicles (UAVs) because of the high power-to-weight ratio, self-balancing ability, and safety of such engines. The design and optimization of combustion systems are crucial for power, fuel economy, and knock control. To meet the increasing demand for UAV power systems and fill the research void in this area, reported here for the first time are the design and optimization of a swirl-wall-guided combustion system including the spray pattern and pit structure on the top surface of the piston, with the dynamic, fuel economy, and knock intensity as the evaluation indicators. The results indicate that the spray pattern mainly affects the fuel escape rate and inhomogeneity. After it is injected into the pit, the fuel is guided to the combustion chamber by the steering role of the guide arc. If the spray drop point is located away from the pit, it leads to increased fuel escape rate and inhomogeneity. The turbulent kinetic energy in the spark-plug zone decreases as the pit diameter decreases, fluctuating by 48 %, while the average value remains relatively constant. The distribution is influenced primarily by the enveloping effect of the pit structure on the airflow. Under low-speed conditions, as the pit diameter decreases, the ignition delay period increases and then decreases, and the combustion duration decreases monotonically. The fluctuation of indicated power is relatively small (2.64 %), and the fuel escape rate decreases monotonically, resulting in the same variation pattern of indicated specific fuel consumption (ISFC). When the pit diameter is 43 mm, the fuel escape rate and ISFC reach their lowest values. Knock combustion near the wall is influenced mainly by two factors: the temperature rise rate and the flame propagation speed. The temperature rise rate increases significantly with decreasing pit diameter. When the pit diameter is less than 50 mm, knock combustion begins to occur. Under high-speed equivalent combustion conditions, as the pit diameter decreases, the indicated power changes by 5.21 %, and the ISFC decreases monotonically.

Controlling Long-Term Plasticity in Neuromorphic Computing Through Modulation of Ferroelectric Polarization.

Electrolyte-gated transistors (EGTs) have significant potential for neuromorphic computing because they can control the number of ions by mimicking neurotransmitters. However, fast depolarization of the electric double layer (EDL) makes it difficult to achieve long-term plasticity (LTP). Additionally, most research utilizing organic ferroelectric materials has been focused on basic biological functions, and the impact on nonvolatile memory properties is still lacking. Herein, we present a polyvinylidene fluoride (PVDF)-based ion-gel synaptic device using PVDF and poly(vinylidene fluoride-co-hexafluoropropylene) (P(VDF-HFP)) to implement LTP through the introduction of ferroelectric materials. The PVDF-based polymer slows the escape rate of TFSI anions from the electrolyte/channel layer through residual polarization. The fabricated synaptic devices successfully demonstrate LTP by controlling ion adsorption under the influence of PVDF-based polymers. Furthermore, it implements synaptic functions including paired pulse facilitation (PPF), high-pass filtering, and neurotransmitter control. To validate the potential of neuromorphic computing, we successfully achieved high recognition rates for artificial/convolutional neural network (A/CNN) simulations via sequential adsorption and desorption under ferroelectric polarization with long-term potentiation/depression (LTP/D). This study provides a rational ion adsorption strategy utilizing the ferroelectric polarization caused by the introduction of a PVDF-based polymer in the dielectric layer.

Atmospheric escape in hot Jupiters under sub-Alfvénic interactions

ABSTRACT Hot Jupiters might reside inside the Alfvén surface of their host star wind, where the stellar wind is dominated by magnetic energy. The implications of such a sub-Alfvénic environment for atmospheric escape are not fully understood. Here, we employ 3D radiation-magnetohydrodynamic simulations and Ly-$\alpha$ transit calculations to investigate atmospheric escape properties of magnetized hot Jupiters. By varying the planetary magnetic field strength ($B_\mathrm{p}$) and obliquity, we find that the structure of the outflowing atmosphere transitions from a magnetically unconfined regime, where a tail of material streams from the nightside of the planet, to a magnetically confined regime, where material escapes through the polar regions. Notably, we find an increase in the planet escape rate with $B_\mathrm{p}$ in both regimes, with a local decrease when the planet transitions from the unconfined to the confined regime. Contrary to super-Alfvénic interactions, which predicted two polar outflows from the planet, our sub-Alfvénic models show only one significant polar outflow. In the opposing pole, the planetary field lines connect to the star. Finally, our synthetic Ly-$\alpha$ transits show that both the red-wing and blue-wing absorptions increase with $B_\mathrm{p}$. Furthermore, there is a degeneracy between $B_\mathrm{p}$ and the stellar wind mass-loss rate when considering absorption of individual Ly-$\alpha$ wings. This degeneracy can be broken by considering the ratio between the blue-wing and the red-wing absorptions, as stronger stellar winds result in higher blue-to-red absorption ratios. We show that, by using the absorption ratios, Ly-$\alpha$ transits can probe stellar wind properties and exoplanetary magnetic fields.

Enhancing possum capture rates with chain springs on leghold traps

ABSTRACT Leghold traps are an essential tool for managing brushtail possums (Trichosurus vulpecula) in New Zealand. However, the currently used trap design (No 1 double coil spring traps, often called Victor-type traps) has escape rates of up to 26%. This study focussed on addressing the high escape rate to improve the usefulness and acceptability of these traps. Specifically, modifications were made to the anchoring chain of the standard No 1 trap by adding one or two springs. These springs were designed to reduce the forces exerted by an animal during escape attempts. Over approximately 300 trap nights per trap configuration (unmodified No-Spring, 1-Spring, 2-Springs), the capture rates (proportion of animals caught and held until inspection) were measured. The results showed that traps with one or two springs achieved a significantly higher capture rate of 92%, compared to only 74% for the standard devices. The chain springs increased the capture rate by 24% due to a 69% reduction in escape rate. This study demonstrates that a minor modification (addition of one or two springs) to the restraining chain of No 1 double coil spring leghold traps greatly enhances their efficacy for capturing and managing possums.

Research on water droplet interception mechanism of sheet-type drift eliminator based on three-dimensional transient numerical simulation

A three-dimensional transient numerical study was conducted on the sheet-type drift eliminator single-channel to reveal the droplet interception mechanism, using a mechanical draft wet cooling tower (MDWCT) as a typical operating environment. The droplet-air, droplet-droplet, droplet-film, and film-air interactions were considered comprehensively from the aerodynamics and heat transfer. The results indicate the existence of two distinct types of droplet escape: primary escape and secondary escape. The Stokes number (St) ≤ 1 for the vast majority of primary escaped droplets, whereas the secondary escaped droplets exhibit a considerable range of St. The correlation curves between the escape rate and the Stokes number (Stin) is similar under different inlet velocities (vin). The escape rate first decreases and then increases as Stin increases. There is a safety zone (Stin from 0.83 to 18.62) where the escape rate is near zero. For the studied eliminator, the specific safety zone is 65∼190 μm. The mass flow rate of escaped droplets first decreases and then increases as vin increases. The secondary escape dominates instead of primary escape when vin ≥ 7 m/s. This paper provides theoretical support for improving interception efficiency of eliminator while extending the methods for drift reduction and water savings.

A novel extended social force model for studying the impact of the heterogeneity of pedestrian physical fitness on emergency evacuation efficiency

Emergencies in public places, particularly confined crowded areas, will disrupt the stability of dense crowds and consequently lead to accidents. To promote public emergency safety, there is a pressing need for efficient modeling methods to investigate the evacuation mechanism in these places and improve the social public safety. This study proposes a Physical Fitness Heterogeneity based Social Force Model (PFH-SFM) that takes into account the heterogeneous desired evacuation velocity caused by the heterogeneity of pedestrian physical fitness, by means of developing the normalized desired velocity ratio. Then, we use PFH-SFM to investigate the relationships between the escape rate and the desired velocity, and between the evacuation duration and the desired velocity in terms of various group sizes with heterogeneous physical fitness, the relationship between the percentage of reduction in evacuation duration and desired velocity when including weak pedestrians, the pedestrian distribution in the evacuation process, the relationship between the total evacuation duration and the desired velocity in terms of various proportions of weak pedestrians and the relationship between the evacuation duration and the desired velocity in terms of various normalized starting and ending velocity ratios by considering various group sizes, respectively. The findings of this study show that the existence of a certain small proportion of pedestrians with weak physical fitness can promote global evacuation dynamics, especially in the case of high crowded density, and can reduce evacuation duration by up to 20% in our experiments. Additionally, when the percentage of pedestrians with weak physical fitness is relatively high, they tend to have a detrimental effect on the evacuation efficiency. Furthermore, there exists a moderate normalized desired starting velocity ratio that maximizes the overall evacuation efficiency; on the other hand, the lower the normalized desired ending velocity ratio is, the more efficient the evacuation is. To the best of the authors’ knowledge, this study is the first time to introduce the concepts of normalized desired starting and ending velocity ratios and innovatively analyzes the impact of the continuously changing desired velocity of pedestrians on the evacuation efficiency in multi-exit scenarios. The results offer valuable insights for relevant stakeholders to formulate effective evacuation plans, so as to enhance urban emergency capacity and minimize social and economic losses.

Generalised Lyapunov stretching in a weakly chaotic open dynamical system

Abstract Chaotic dynamical systems may be characterised by a positive Lyapunov exponent, which measures the exponential rate of separation of nearby trajectories. However in a wide range of so-called weakly chaotic systems, the separation of nearby trajectories is sub-exponential, for example stretched exponential, in time; and therefore in such cases the Lyapunov exponent vanishes. When a hole is introduced in chaotic systems, the Lyapunov exponent on the system’s fractal repeller can be related to the generation of entropy and the escape rate from the system via the escape rate formalism, but no suitable generalisation exists to weakly chaotic systems. In this work we show that in a paradigmatic one-dimensional weakly chaotic iterated map, the Pomeau-Manneville map, the generation of generalised Lyapunov stretching is completely suppressed in the presence of a hole. These results are shown based on numerical evidence, and explained with a fully analytic stochastic model.

Numerical Evaluation of Aerosol Propagation in Wind Instruments Using Computational Fluid Dynamics

This paper examines aerosol propagation in wind instruments through numerical analysis, focusing on particle trajectories within five types of wind instruments: saxophone, clarinet, flute, oboe, and trumpet. Using a computational fluid dynamics approach, it is found that larger particles are deposited within the instruments, while smaller micron-sized particles predominantly exit through the bell. The impact of the instrument’s geometry on aerosol dynamics is quantified; cylindrical instruments (clarinet, flute) show an increased rate of small droplet deposition or escape through tone holes compared to conical instruments (saxophone, oboe). Instruments with steep turnings, such as the trumpet, exhibited significant particle deposition. The study suggests that deposited particles are likely to move towards re-emission points, driven by gravity and airflow, especially in straight-shaped instruments. Integrating computational fluid dynamics (CFD) as a complementary approach to traditional experimental methods provides insights into aerosol transmission mechanisms in musical settings. This methodology not only aids in understanding aerosol behavior but also supports the development of safer musical and educational environments, contributing to the field.

Thermodynamics of chaotic relaxation processes.

The established thermodynamic formalism of chaotic dynamics, valid at statistical equilibrium, is here generalized to systems out of equilibrium that have yet to relax to a steady state. A relation between information, escape rate, and the phase-space average of an integrated observable (e.g., Lyapunov exponent, diffusion coefficient) is obtained for finite time. Most notably, the thermodynamic treatment may predict the phase-space profile of any integrated observable for finite time, from the leading and subleading eigenfunctions of the Perron-Frobenius or Koopman transfer operator. Examples of that equivalence are shown, and the theory is tested analytically on the Bernoulli map while numerically on the perturbed cat map, the Hénon map, and the Ikeda map, all paradigms of chaos.

Numerical Investigation on Transient Flow and Inclusion Removal Behavior in Tundish During Ladle Change Process

The removal of inclusion particles is an important function of tundish metallurgy. During ladle change, the liquid level fluctuation around the ladle shroud is severe, which may affect the effectiveness of inclusion removal. In the present study, the fluid flow characteristics and inclusion‐removal behavior in the tundish during ladle change are investigated by numerical simulation method. And the effectiveness of flow control devices on the flow characteristics of molten steel is evaluated. It is found that the escape rate of inclusion particles during ladle change is ordered as emptying process < steady process < filling process. The proper combination of weir, dam, and turbulence inhibitor can optimize the conditions for the floating and removal of inclusion particles to the greatest extent. In the tundish with weir and dam, the escape rates of inclusion particles with sizes of 10, 50, and 100 μm throughout the entire ladle change period are respectively reduced by 9.8%, 1.6%, and 1.4%, compared to not using flow control devices. With a combination of weir, dam, and turbulence inhibitor, the escape rates of the three types of inclusion particles are reduced by 24.7%, 9.9%, and 1.2%, respectively.

Nitrogen Loss from Pluto’s Birth to the Present Day via Atmospheric Escape, Photochemical Destruction, and Impact Erosion

We estimate the loss of nitrogen from Pluto over its lifetime, including the giant planet instability period, which we term the “Wild Years.” We analyze the orbital migration of 53 simulated Plutinos, which are Kuiper Belt Objects (KBOs) captured into 3:2 mean-motion resonance with Neptune during the instability. This orbital migration brought the Plutinos from 20 to 30 au to their present-day orbits near 40 au along a nonlinear path that includes orbits with semimajor axes from 10 to 100 au. We model the thermal history that results from this migration and estimate the volatile loss rates due to the ever-changing thermal environment. Due to the early Sun’s enhanced ultraviolet radiation, the photochemical destruction rate during the Wild Years was a factor of 100 higher than the present-day rate, but this only results in a loss of ∼10 m global equivalent layer (GEL). The enhanced Jeans escape rate varies wildly with time, and a net loss of ∼100 cm GEL is predicted. Additionally, we model the impact history during the migration and find that impacts are a net source, not loss, of N2, contributing ∼100 cm GEL. The 100 cm GEL is 0.1% of the amount of N2 in Sputnik Planitia. We therefore conclude that Pluto did not lose an excessive amount of volatiles during the Wild Years, and its primordial volatile inventory can be approximated as its present-day inventory. However, significant fractions of this small total loss of N2 occurred during the Wild Years, so estimates made using present-day rates will be underestimates.

The Effect of the Interplanetary Magnetic Field Clock Angle and the Latitude Location of the Intense Crustal Magnetic Field on the Ion Escape at Mars: An MHD Simulation Study

AbstractIn this paper, using a three‐dimensional multifluid MHD model, we studied the effects of the interplanetary magnetic field (IMF) clock angle and the latitude position of the intense crustal magnetic field (ICMF) on the escape of ions O+, , and at Mars. The main results are as follows: (a) The IMF clock angle affects the ion escape at Mars. When the ICMF is on the dayside, the ion escape rate reaches a maximum at the IMF clock angles close to 60°–90° and a minimum at the IMF clock angles close to 120°–150°, because the ICMF can change the topology of the magnetic field and affect the interaction between the solar wind and Mars. The difference between the maximum and minimum ion escape rates due to the IMF clock angle can reach over 50%. (b) Compared with the −ESW hemisphere, the escape flux of and in the +ESW hemisphere is more significant. However, O+ generally has a larger escape flux in the −ESW hemisphere. The different results in the ±ESW hemispheres might be due to the larger distribution of the hot oxygen corona, which changes the flow pattern of O+. (c) The latitude location of the ICMF can also affect the ion escape. When the ICMF is on the dayside, as the subsolar point varies from 25°S to 25°N, that is, the intense crustal magnetic field position keeps shifting southward, the ion escape rate shows a gradual increase.

Topology and phase transition for EPYM AdS black hole in thermal potential

As we all know the local topological properties of thermodynamical systems can be expressed by the winding numbers as the defects. The topological number that is the sum of all winding numbers can be used to classify the global topological nature of thermodynamical systems. In this paper, we construct a kind of thermal potential and then put the Einstein-power-Yang-Mills AdS black hole in it. Through the analysis of the geometric characteristics of the thermal potential based on the complex analysis we find the topological number is an invariant that is same as shown in the way of the Duan's ϕ-mapping topological current [Sci. Sin. 9, 1072 (1979)]. Furthermore, we adopt the Kramer's escape rate method to investigate the intensity of the first-order phase transition.

Escape rate of a dimer under the influence of additive colored noise: Ornstein–Uhlenbeck process

The escape process of a dimer is studied in a bistable potential in the presence of additive Ornstein-Uhlenbeck (OU) noise. The escape rate of the dimer shows a non-monotonic dependence with respect to the harmonic spring constant, κ. However, an increase in the correlation time, τ of the OU noise causes a delay in the escape mechanism of the dimer. Another important observation is that the optimal spring constant, kopt, at which the escape rate peaks changes with the correlation time. In summary, a complex interplay between the harmonic force and the correlation time of the OU noise is involved in the escape process of the dimer.

MESSENGER Observations of Mercury's Planetary Ion Escape Rates and Their Dependence on True Anomaly Angle

AbstractThis study investigates the escape of Mercury's sodium‐group ions (Na+‐group, including ions with m/q from 21 to 30 amu/e) and their dependence on true anomaly angle (TAA), that is, Mercury's orbital phase around the Sun, using measurements from MESSENGER. The measurements are categorized into solar wind, magnetosheath, and magnetosphere, and further divided into four TAA intervals. Na+‐group ions form escape plumes in the solar wind and magnetosheath, with higher fluxes along the solar wind's motional electric field. The total escape rates vary from 0.2 to 1 × 1025 atoms/s with the magnetosheath being the main escaping region. These rates exhibit a TAA dependence, peaking near the perihelion and similar during Mercury's remaining orbit. Despite Mercury's tenuous exosphere, Na+‐group ions escape rate is comparable to other inner planets. This can be attributed to several processes, including that Na+‐group ions may include several ion species, efficient photoionization frequency for elements within Na‐group, etc.

Regulatory role of Mycobacterium tuberculosis MtrA on dormancy/resuscitation revealed by a novel target gene-mining strategy.

The unique dormancy of Mycobacterium tuberculosis plays a significant role in the major clinical treatment challenge of tuberculosis, such as its long treatment cycle, antibiotic resistance, immune escape, and high latent infection rate. To determine the function of MtrA, the only essential response regulator, one strategy was developed to establish its regulatory network according to high-quality genome-wide binding sites. The complex modulation mechanisms were implied by the strong bias distribution of MtrA binding sites in the noncoding regions, and 32.7% of the binding sites were located inside the target genes. The functions of 288 potential MtrA target genes predicted according to 294 confirmed binding sites were highly diverse, and DNA replication and damage repair, lipid metabolism, cell wall component biosynthesis, cell wall assembly, and cell division were the predominant pathways. Among the 53 pathways shared between dormancy/resuscitation and persistence, which accounted for 81.5% and 93.0% of the total number of pathways, respectively, MtrA regulatory genes were identified not only in 73.6% of their mutual pathways, but also in 75.4% of the pathways related to dormancy/resuscitation and persistence respectively. These results suggested the pivotal roles of MtrA in regulating dormancy/resuscitation and the apparent relationship between dormancy/resuscitation and persistence. Furthermore, the finding that 32.6% of the MtrA regulons were essential in vivo and/or in vitro for M. tuberculosis provided new insight into its indispensability. The findings mentioned above indicated that MtrA is a novel promising therapeutic target for tuberculosis treatment since the crucial function of MtrA may be a point of weakness for M. tuberculosis.

Staphylococcus aureus persistence in osteocytes: weathering the storm of antibiotics and autophagy/xenophagy.

Staphylococcus aureus is a major causative pathogen of osteomyelitis. Intracellular infections of resident bone cells including osteocytes can persist despite gold-standard clinical intervention. The mechanisms by which intracellular S. aureus evades antibiotic therapy are unknown. In this study, we utilised an in vitro S. aureus infection model of human osteocytes to investigate whether antibiotic-mediated dysregulation of autophagy contributes to this phenomenon. Infected or non-infected osteocyte-like cells were exposed to combinations of rifampicin, vancomycin, and modulators of autophagy. Intracellular bacterial growth characteristics were assessed using colony-forming unit (CFU) analysis, viable bacterial DNA abundance, and the rate of escape into antibiotic-free medium, together with measures of autophagic flux. Rifampicin, alone or in combination with vancomycin, caused a rapid decrease in the culturability of intracellular bacteria, concomitant with stable or increased absolute bacterial DNA levels. Both antibiotics significantly inhibited autophagic flux. However, modulation of autophagic flux did not affect viable bacterial DNA levels. In summary, autophagy was shown to be a factor in the host-pathogen relationship in this model, as its modulation affected the growth state of intracellular S. aureus with respect to both their culturability and propensity to escape the intracellular niche. While rifampicin and vancomycin treatments moderately suppressed autophagic flux acutely, this did not explain the paradoxical response of antibiotic treatment in decreasing S. aureus culturability whilst failing to clear bacterial DNA and hence intracellular bacterial load. Thus, off-target effects of rifampicin and vancomycin on autophagic flux in osteocyte-like cells could not explain the persistent S. aureus infection in these cells.

An Empirical Predictive Model for Atmospheric H Lyman‐α Emission Brightness at Mars

AbstractCharacterizing the abundance of atmospheric hydrogen (H) at Mars is critical for determining the current and, subsequently, the primordial water content on the planet. At present, the atmospheric abundance of Martian H is not directly measured but is simulated using proprietary models that are constrained with observations of H Lyman‐α emission brightness, as well as with observations of other atmospheric parameters, such as temperature and Solar UV irradiance. Publicly available brightness measurements require further processing to have scientific utility. To make the data needed to model H abundances and escape rates more accessible to the community, we use H Lyman‐α emissions made with the Mars Atmosphere and Volatile Evolution (MAVEN) mission. The near decade‐spanning data set is reduced to obtain disk‐pointed averages of the H brightness in the upper atmosphere of Mars and then analyzed for statistical trends across multiple variables. The H Lyman‐α emission brightness is found to be dependent on Solar illumination, Solar cycle, and season. The resulting data trends are used to derive empirical fits to build a predictive framework for future observations or an extrapolative tool for estimates of water content at previous epochs. Data that was intentionally not included in the empirical derivations are used to validate the predictions successfully to within 18% accuracy, on average. This first‐of‐its kind predictive model for H brightness is presented to the community and can be used with atmospheric models to further derive and interpret the abundances and escape rate of H atoms at Mars.

Efficient placement technology of proppants based on structural stabilizers

Fiber is highly escapable in conventional slickwater, making it difficult to form fiber-proppant agglomerate with proppant and exhibit limited effectiveness. To solve these problems, a novel structure stabilizer (SS) is developed. Through microscopic structural observations and performance evaluations in indoor experiments, the mechanism of proppant placement under the action of the SS and the effects of the SS on proppant placement dimensions and fracture conductivity were elucidated. The SS facilitates the formation of robust fiber-proppant agglomerates by polymer, fiber, and quartz sand. Compared to bare proppants, these agglomerates exhibit reduced density, increased volume, and enlarged contact area with the fluid during settlement, leading to heightened buoyancy and drag forces, ultimately resulting in slower settling velocities and enhanced transportability into deeper regions of the fracture. Co-injecting the fiber and the SS alongside the proppant into the reservoir effectively reduces the fiber escape rate, increases the proppant volume in the slickwater, and boosts the proppant placement height, conveyance distance and fracture conductivity, while also decreasing the proppant backflow. Experimental results indicate an optimal SS mass fraction of 0.3%. The application of this SS in over 80 wells targeting tight gas, shale oil, and shale gas reservoirs has substantiated its strong adaptability and general suitability for meeting the production enhancement, cost reduction, and sand control requirements of such wells.

Simulations of the hydrogen and deuterium thermal and non-thermal escape at Mars at Spring Equinox

We present simulations of the thermal and nonthermal escape processes for H and D, under atomic, molecular and ion forms at Mars during spring equinox. These processes include Jeans escape, several photochemical reactions and the escape associated to the solar wind interaction with Mars. While the hydrogen escape is dominated by the atomic Jeans escape, we find that the deuterium escape is dominated by the photochemical atomic escape. Ions escape represent only 10% of the total escape for both species and is mostly due to charge exchange between neutral and solar wind protons. Including all the processes, we find a D/H fractionation factor (D/H escape ratio divided by the D/H atmospheric ratio) f = 0.04, with a main uncertainty associated to the elastic collisional cross sections needed to accurately derive the photochemical escape rate. Using this fractionation factor and considering a 30 m exchangeable reservoir of water, the average hydrogen escape rate needed to fractionate the Martian water from its primordial value to its current D/H value during the last 4.5 Gyr is ∼1.0 × 1028 s−1 which is larger than the current average escape rate (∼ 2 × 1026 s−1).