Moderate Speed Research Articles

Preliminary assessment of volatile organic compounds and hazardous gases dispersion at low winds: case study of Mellitah Gas Complex, Libya

Air pollution from industrial areas has become really worrying especially for city dwellers. The plume dispersion emitted from industrial sources is subject to several factors: temperature and emission rate velocity, wind speed and direction, source height, and atmospheric stability. This study aimed to evaluate the applicability of the dispersion coefficients correlated within a Gaussian plume approach to an industrial source in Libya (Mellitah Gas Complex) under low and moderate wind speeds. To this end, we have developed a specific code based on the Gaussian method to study the dispersion of (1) Volatile Organic Compounds (VOCs) from oil storage tanks and condensate storage tanks, and (2) sulfur oxides (SOx) and nitrogen oxides (NOx) emitted by the flaring process through three stacks of 80 m height. The emissions from multisource points and their dispersion have been predicted at calm wind conditions and the flammability and danger-prone toxic zones have been delimited around the studied site. The obtained results reveal that the emissions, particularly generated at low and moderate wind speeds, induce a dispersion with high concentration levels in the area surrounding the industrial site. The VOCs critical concentration region indicates a real risk of flammability at low-speed wind and stable atmospheric condition, from a height of 5 m above the ground. In fact, the VOCs concentration reach the Flammability Inferior Limit value of 0.018 m3 VOCs/m3 and these concentrations, appearing in the form of a plume, extend downstream to approximately 1000 m. The dispersion of NOx and SOx emissions downwind from the stacks are enhanced by wind speed; nevertheless, at 2 m height from the ground, the levels could exceed the limit value of 0.125 mg/m3, especially under the condition of unstable and very unstable atmospheric classes. From our findings, we recommend continuous monitoring campaigns inside and around the complex of Mellitah to ensure an environmentally secure zone that respects safety and health guidelines. Furthermore, enhanced simulations based on hourly weather conditions for extended area would be of great interest to accurately assess the air quality index in the region.

Effect of extension speed on the mechanical performance of sisal and coir fiber bundles

Quasi-static tensile tests are commonly used to determine the mechanical properties of fiber bundles. These tests are generally carried out at a low standard speed of 1 mm.min−1, which is recommended for elementary fibers, although other moderate and high speeds are rarely used. In this study, tensile tests were carried out on coir and sisal fiber bundles from the coastal region of Cameroon using four different speeds: 1, 2, 5, and 10 mm.min−1 to assess mechanical properties. Samples were prepared by attaching the two ends of each randomly selected fiber bundle to a paper frame to obtain a length of 30 mm. The results showed a significant effect of extension speed, indicating a decrease in tensile strength and Young’s modulus, and an increase in strain at break with increasing speed. These trends were correlated with the power functions. A strong dependence between fiber bundle diameter and tensile strength was also observed. Furthermore, statistical analysis based on the Weibull distribution highlighted the dispersion of mechanical properties, demonstrating a reduction in dispersion with increasing extension speed for coir fibers. These data can be used to develop specific standards for these natural fibers and contribute to the advancement of composites based on plant fibers.

Impact of nutrition intervention on the nutritional status and cognitive function among children (6-12 years) – An Interventional Study from South India

Aim: The aim of this study was to prepare Methotrexate and triherbal loaded topical emulgels for anti-arthritic activity. Methods: The above sources are subjected to soxhlation and aqueous and hydroalcoholic extracts of the above three will be prepared. The extracts will be prepared by proper maceration in suitable solvents in required proportions. The resultant extract will be converted into emulgel as follows: The gel portion of the emulgel will be made by dissolving carbopol-934 in cold water with constant stirring at a moderate speed until uniform mixture is obtained. The pH was then adjusted to 6–6.5 using triethanolamine (TEA). Tween 80 was dissolved in distilled water to prepare the aqueous phase of the emulsion while for the preparation of the oil phase of the emulsion; span 80 was dissolved in liquid paraffin. To preserve the emulsion, benzalkonium chloride was dissolved in water and the suitable amounts of extracts and methotrexate is dissolved in ethanol then both solutions are mixed with the aqueous phase. Both the aqueous and the oil phase were heated in a water bath at 70 °C separately. Then the oil phase was added drop wise to the aqueous phase with continuous stirring using homogenizer at speed of 3000 rpm for 10 min then cold to room temperature. At the end the gel and emulsion portions were mixed in 1:1 ratio with moderately stirring to prepare emulgel. The preparation is made viscous to be spreadable on the skin sufficiently without friction by trial-and-error way of mixing different proportions of gelling polymers. The formulation thus prepared is subjected to suitable characterization and evaluation studies and the optimized formulation is reported after obtaining results. Results: Drug-polymer compatibility studies (FT-IR and DSC) showed no incompatibility between the drug and polymer. In- vitro permeation studies though egg membrane showed good drug release in the range of 78.91 to 98.92% over a period of 2 hours. The best formulation was found to be F3 showing in-vitro drug release of 98.92%. The correlation and coefficient (R2) values obtained from the kinetic equation shows the drug release from all the formulation (F1-F9) follow zero order drug release mechanism. Conclusion: It can be concluded that Methotrexate and Triherbal loaded Topical emulgels could be a better formulation approach for Anti-arthritic activity.

Perceptual transitions between object rigidity and non-rigidity: Competition and cooperation among motion energy, feature tracking, and shape-based priors.

Why do moving objects appear rigid when projected retinal images are deformed non-rigidly? We used rotating rigid objects that can appear rigid or non-rigid to test whether shape features contribute to rigidity perception. When two circular rings were rigidly linked at an angle and jointly rotated at moderate speeds, observers reported that the rings wobbled and were not linked rigidly, but rigid rotation was reported at slow speeds. When gaps, paint, or vertices were added, the rings appeared rigidly rotating even at moderate speeds. At high speeds, all configurations appeared non-rigid. Salient features thus contribute to rigidity at slow and moderate speeds but not at high speeds. Simulated responses of arrays of motion-energy cells showed that motion flow vectors are predominantly orthogonal to the contours of the rings, not parallel to the rotation direction. A convolutional neural network trained to distinguish flow patterns for wobbling versus rotation gave a high probability of wobbling for the motion-energy flows. However, the convolutional neural network gave high probabilities of rotation for motion flows generated by tracking features with arrays of MT pattern-motion cells and corner detectors. In addition, circular rings can appear to spin and roll despite the absence of any sensory evidence, and this illusion is prevented by vertices, gaps, and painted segments, showing the effects of rotational symmetry and shape. Combining convolutional neural network outputs that give greater weight to motion energy at fast speeds and to feature tracking at slow speeds, with the shape-based priors for wobbling and rolling, explained rigid and non-rigid percepts across shapes and speeds (R2 = 0.95). The results demonstrate how cooperation and competition between different neuronal classes lead to specific states of visual perception and to transitions between the states.

Performance Analysis of 2 U-Type Savonius Blades for Vertical Rotor Wind Turbine

Renewable, unlimited and environmentally safe, wind energy is referred to as renewable energy. In Indonesia, wind speeds between 3 to 7 m/s are considered moderate wind speeds. Wind turbines can be used to convert wind energy into electrical energy. The Savonius rotor is cylindrical and has two or more blades attached. The purpose of this study is to determine the power, torque, and rotation per minute produced by a Savonius rotor wind turbine with a blade radius of 50 cm and a blade height of 100 cm. Wind speeds of 3 m/s, 5 m/s, 7 m/s, 9 m/s, 11 m/s, 13 m/s, and 15 m/s were used for testing. A tachometer was used to measure rpm, while a loadcell sensor measured torque and power data. Based on the research findings, it was found that each wind speed variation produced a different average rotor rotation per minute. The rotor speed, torque, and power increased with increasing wind speed.

Flutter limitation of drag reduction by elastic reconfiguration

Through experiments, we idealize a plant leaf as a flexible, thin, rectangular plate clamped at the midpoint and positioned perpendicular to an airflow. Flexibility of the structure is considered as an advantage at moderate flow speed because it allows drag reduction by elastic reconfiguration, but it can also be at the origin of several flow-induced vibration phenomena at higher flow speeds. A wind tunnel campaign is conducted to identify the limitation to elastic reconfiguration that dynamic instability imposes. Here, we show by increasing the flow speed that the flexibility permits a considerable drag reduction by reconfiguration, compared to the rigid case. However, beyond the stability limit, vibrations occur and limit the reconfiguration. This limit is represented by two dimensionless numbers: the mass number and the Cauchy number. Our results reveal the existence of a critical Cauchy number below which static reconfiguration with drag reduction is possible and above which a dynamic instability with important fluctuating loads is present. The critical dimensionless velocity is dependent on the mass number. Flexibility is related to the critical reduced velocity and allows defining an optimal flexibility for the structure that leads to a drag reduction by reconfiguration while avoiding dynamic instability. Furthermore, experiments show that our flexible structure can exhibit two vibration modes: symmetric and anti-symmetric, depending on its mass number. Because the system we consider is bluff yet aligned with the flow, it is unclear whether the vibrations are due to a flutter instability or vortex-induced vibration or a combination of both phenomena.

Elucidating Morphology‐Mobility Relationships of Organic Thin Films Through Transfer Learning‐Assisted Multiscale Simulation

AbstractUnderstanding the relationship between morphology and charge transport capability in organic thin films is vital for advancements in organic electronics. However, accurately predicting charge mobility in these films is challenging due to the extensive evaluations of transfer integral required. To address this challenge, transfer learning techniques are employed to develop machine learning models capable of efficiently and accurately calculating transfer integrals in organic thin films with grain boundaries and polymorphs. Through machine learning‐assisted multiscale simulations of charge transport, the impact of solution shearing conditions is investigated on the morphology and mobility of organic thin films. The findings reveal that shearing‐induced molecular orientation and pre‐aggregation have a significant influence on film morphology, and a moderate shearing speed combined with a suitable solvent promotes the formation of extended transport networks, leading to higher mobility. The utilization of transfer learning‐accelerated simulation techniques opens up new possibilities for exploring the relationship between solution‐processing conditions, morphology, and charge transport properties of organic thin films. This research provides valuable insights that can be applied to optimize solution‐processing techniques in organic electronics.

Tyre lateral slip effect on off-tracking of a long combination vehicle

This paper evaluates the effect of tyre lateral slip on the off-tracking of a long combination vehicle (LCV) consisting of a semi-truck with 28-ft double trailers. A geometric model of LCV motion neglecting tyre slip and a high-order multi-body dynamic model in TruckSim® including tyre slip are developed and validated against other simulation and field test data. Tyre slip effect on off-tracking is measured by comparing the models' estimated off-tracking when the LCV netogiates 50, 75 and 100 ft (15.24, 22.86, and 30.48 m) radius curves at speeds of 1–16mph (1.6–25 km/hr). Two trailer payloads – 6000 lb/trailer and 14,500 lb/trailer – and three tyre-road friction coefficients – 0.85, 0.45 and 0.65 – were simulated. The simulation results indicate that tyre lateral slip increases – and thus off-tracking decreases – approximately to the second-order of vehicle speed for a given curve radius. It is also found that tyre lateral slip is negligible for speeds below 3–4mph (5–6 km/hr) in all simulated conditions. Additionally, as the path radius increases, tyre lateral slip and vehicle off-tracking sensitivity to vehicle speed reduce. The results suggest that for moderate speeds (>7mph (11 km/hr)), increasing vehicle payload and reducing surface friction coefficient result in an increase in tyre lateral slip that consequently reduces off-tracking.

Dynamic analysis of Caribbean food import demand

Short- and long-run price and income elasticities are generally unavailable at the regional level for major imported food groups for the Caribbean. These elasticity measures are needed to enhance policymaking. This paper therefore seeks to determine the income, own-price and cross-price elasticities of eight major imported food groups. This will show the relationships between income and price changes on the import quantities for the major food groups. This was done using an error-corrected linear approximate almost ideal demand system (EC-LA-AIDS) for the period 1961–2021, using annual data. The study found that the theoretical restrictions of homogeneity and symmetry did not hold in the static LA-AIDS model but did in the EC-LA-AIDS model. The speed of adjustment parameter in the EC-LA-AIDS model revealed that imported beverages had the slowest adjustment to long-run equilibrium while all other imported food categories had a moderate adjustment speed. The study also derived short- and long-run income and price elasticities of import demand for the eight imported food categories. In both time horizons, income elasticities revealed that all imported food categories were normal goods. In both time horizons, imported meat and seafood, and sugar and honey were the most responsive to changes in income, while spices and tea was the least responsive. Own-price elasticities revealed that all imported food categories were import price inelastic except for meat and seafood which was found to be import price elastic in both time horizons. Additionally, cross-price elasticities unveiled various substitution and complementary relationships between pairs of imported foods. The study not only contributed empirical insights into the import demand dynamics of the Caribbean, but also emphasized significant policy implications arising from the research findings.

Nonlinear response of hydraulic turbine generator set caused by unbalanced magnetic pull and oil film force

Hydraulic turbine generator sets are crucial for harnessing water energy. However, the nonlinear phenomena resulting from the combination of unbalanced magnetic pull (UMP) and oil film forces remain unclear. A mathematical model of the rotor-bearing system is introduced to investigate the effects of UMP and the nonlinear oil film force on system. The UMP and nonlinear oil film force are derived from the air-gap magnetic energy and short bearing theory, respectively. The proposed model is verified by the stability experiments of hydraulic turbine generator set in the idling, no-load, and load conditions. The results show that, firstly, the system turns unstable for oil whip and oil swirl, and which experiences bifurcation and undergoes dynamical motions such as period-1 to period-5, quasi-periodic, and chaotic motions. Then, at moderate speeds, the rotor eccentricity has the greatest effect on the bifurcation at idle. While the nonlinear characteristics of the system are most sensitive to the rotor eccentricity at loaded condition. Finally, the existence of UMP reduces the instability caused by oil film forces.

Restoring statistical cyclicity in rotating machinery vibrations using the oscillatory almost-cyclostationary model

Speed fluctuations will affect the statistical characteristics of rotating machinery vibrations, resulting in fuzzy fault features that are difficult to extract. This type of feature ambiguity can be interpreted as the vibrations are warped in time, and the related signal model is described as a time-warped almost-cyclostationary (ACS) process. By employing this sophisticated model in a de-warping procedure, the regular statistical properties of the signal are restored. In this paper, we exploit the de-warping method of Napolitano for restoring fault features of rotating machinery under fluctuating speed conditions. Notice that the time-warped ACS process belongs to a subclass of the oscillatory ACS signal model. More specifically, under moderate speed fluctuation conditions, rotating machinery signals are further characterized as modulated cyclical signals. Therefore, the de-warping can be achieved by demodulating the time-varying autocorrelation function. The approach avoids directly estimating the warping function by the complex non-convex optimization problem. Meanwhile, the accuracy of the solution is guaranteed. More clustered features lead to a more efficient diagnosis. In addition, the rotating speed can also be derived from the warping function without using a tachometer. Case studies of the experiments on a conventional bearing and a turbopump bearing with a large DN-value confirm the feasibility of the oscillatory ACS signal model. Furthermore, the superiority of the de-warping method is corroborated by the enhanced fault features in the classical cyclic spectrum analysis.

Novel study on investigating the mechanical, microstructure morphological, and dry sliding wear characteristics of grey cast iron GG25 with copper additions for valve guides in internal combustion engine

Introduction: The performance functionality efficacy of the engine’s valve train assembly is considerably affected by the valve guide. Material selection is impacted by the prolonged operational lifespan of engines, which favours casting and machining materials such as cast iron. The intent of this study is to examine the dry sliding characteristics of GG25 cast iron with copper additives. Discovering the ways in which variations in load and sliding velocity impact wear characteristics is of paramount significance.Methods: The research entailed the examination of wear characteristics across various environmental conditions. Loads were varied at 30 N, 40 N, and 50 N while maintaining a 1 m/s velocity constant. In the same manner, sliding velocities of 0.5 m/s, 1 m/s, and 2 m/s were varied while a constant load of 30 N was maintained. Experimental techniques were carried out at ambient temperature. Throughout the investigations, frictional forces and the coefficient of friction were also determined. The wear mechanisms of samples that had become deteriorated or worn-out were examined by employing a scanning electron microscope when combined with EDX analysis.Results: A rise in the normal load from 30 N to 40 N led to a twofold rise in wear losses, measuring 417 microns as compared with 222 microns previously. The range of wear losses observed at moderate speeds (0.5 m/s–1 m/s) was 133–222 microns. Conversely, the maximum wear loss observed was 1,226 microns at elevated sliding velocities of 2 m/s, in contrast to 617 microns at higher normal loads of 50 N. Additionally, the research discovered that normal load is more pronounced when both loading and speed are moderate, whereas sliding speed becomes more substantial when both are raised, culminating to higher wear losses.Discussions: In summary, the research highlights the considerable effect that normal load and sliding speed have on the prevalence of wear losses. In conditions of moderate loading and velocity, the influence of normal load is more significant. However, as sliding accelerates, it becomes the predominant factor. An analysis of frictional forces as well as the coefficient of friction indicated that under loading conditions of 30 N–50 N, the friction coefficient raised from 0.238 to 0.43. The wear mechanisms, as discerned via scanning electron microscopy and EDX analysis, underscored the considerable impact of increased sliding velocity on wear loss in comparison to conditions of higher loading.

Synchronizing Renewable Energy Sources in Distributed Generation Systems.

In renewable and distributed generation systems the grid voltage quality can be poor. So, the connection of power converters to the grid requires accurate control of synchronism between the two sources. The paper discusses issues on synchronization of power converters connected to the mains and related control methods. The design and experimentation of a prototype of a 200 kW power converter that connects a wind generator to the grid help to validate the adopted approach. In this paper a new zero crossing synchroniser is proposed having zero error in steady state, moderate speed response to grid frequency changes and amplitude voltage variations, and harmonics and noise immunity. The speed response, and harmonics and noise immunity are a trade-off. Simulation results with strong disturbances in the grid voltage show the robustness of the proposed method.

Power Loss Analysis of an Oil-Jet Lubricated Angular Contact Ball Bearing: Theoretical and Experimental Investigations

This study presents a theoretical and experimental analysis to quantify the power losses generated by an oil jet lubricated angular contact ball bearing. The analysis is conducted for a moderate speed range (N∙dm product less than 106) and a limited applied load (<5% of the static capacity). The lubrication regime of each ball is studied through a theoretical model and varies from Iso-Viscous Rigid to Elasto-Hydrodynamic. Therefore, the hydrodynamic effects are considered in the power loss calculation. An experimental campaign is carried out and the influence of several parameters (applied load, oil injection temperature, speed, etc.) is studied. A good agreement is found between the developed model and the measurements. It is shown that the radial applied load has no influence on power losses, unlike speed and axial load. This can be explained by the load distribution and the hydrodynamic rolling contribution on the low loaded balls.

Distribution of common pipistrelle (Pipistrellus pipistrellus) activity is altered by airflow disruption generated by wind turbines.

The mechanisms underlying bat and bird activity peaks (attraction) or losses (avoidance) near wind turbines remain unknown. Yet, understanding them would be a major lever to limit the resulting habitat loss and fatalities. Given that bat activity is strongly related to airflows, we hypothesized that airflow disturbances generated leeward (downwind) of operating wind turbines-via the so-called wake effect-make this area less favorable for bats, due to increased flight costs, decreased maneuverability and possibly lower prey abundance. To test this hypothesis, we quantified Pipistrellus pipistrellus activity acoustically at 361 site-nights in western France in June on a longitudinal distance gradient from the wind turbine and on a circular azimuth gradient of wind incidence angle, calculated from the prevailing wind direction of the night. We show that P. pipistrellus avoid the wake area, as less activity was detected leeward of turbines than windward (upwind) at relatively moderate and high wind speeds. Furthermore, we found that P. pipistrellus response to wind turbine (attraction and avoidance) depended on the angle from the wake area. These findings are consistent with the hypothesis that changes in airflows around operating wind turbines can strongly impact the way bats use habitats up to at least 1500 m from the turbines, and thus should prompt the consideration of prevailing winds in wind energy planning. Based on the evidence we present here, we strongly recommend avoiding configurations involving the installation of a turbine between the origin of prevailing winds and important habitats for bats, such as hedgerows, water or woodlands.

Hydrodynamic and thermal performance analysis of an inclined anchor impeller designed for yield stress food mixing applications

Mechanical agitation and mixing operations are basic processes in many industrial activities, especially in food industry. Agitation of food products with a non-Newtonian yield stress fluid and/or with a high viscosity is a common operation where standard anchor impellers are usually implemented to scrape the lateral surface of the tank. The flow generated by this type of impellers is predominantly tangential, particularly with the presence of Bingham fluids. In this regard, the present research gives a numerical investigation of the laminar flow and heat transfer of a Bingham fluid in a mechanically agitated tank equipped with an inclined anchors configuration, including the standard case. This configuration is intended for the enhancement of the axial flows specifically in the lower part of tanks, while keeping the main operation of scraping. Moreover, for heating process, the agitated system is equipped with a lateral jacket system where the temperature remains constant over time. The effects of the Bingham and Richardson numbers as well as of the anchor inclination angle are analyzed on the hydrodynamic and thermal stats. The differential balances that govern the studied phenomenon including continuity, momentum and energy equations are solved by the use of Galerkin finite element method. The results demonstrate the hydrodynamic, energetic, and thermal benefits of agitating yield stress fluids using an inclined base anchor. Indeed, significant axial hydrodynamic generation is observed with a reduced energy consumption of approximately 30% compared to the standard anchor, particularly at moderate rotational speeds. Furthermore, it enhances thermal insulation inside the mixing system and hence promoting heating process, especially in the presence of Bingham fluid and buoyancy force.

Biological sex-related differences in whole-body coordination during standing turns in healthy young adults

Biological sexes (male and female) have been reported to influence postural control and balance due to differences in musculoskeletal structures, hormonal factors, and neuromuscular control. These factors can contribute to the turning performance, potentially leading to an increased incidence of falls, particularly during turning. Therefore, this study aimed to explore the whole-body coordination and stepping characteristics and during standing turns in healthy adults to determine the effects of biological sex and turn speed. Fifty participants (25 males and 25 females) completed 180° standing turns on level ground. Inertial Measurement Units (XSENS) were used to measure whole-body movement turning kinematics and stepping characteristics. Moreover, clinical outcome of dynamic balance was measured by the Timed Up and Go (TUG). Participants were randomly tasked to turn at three speeds; fast, moderate, or slow to the left and right sides. Mann–Whitney U tests were used to compare the independent variables between male and females, and Friedman tests with Dunn’s tests for pairwise comparisons were used to compare between the three turning speeds within the two groups. The results demonstrated that significant differences were seen between males and females during fast turning for the leading foot onset (p = 0.048) and in the slow speed for the total step (p = 0.033), showing that these were greater in female with an increase in turn speed. In addition, significant differences were seen only in the males when comparing different speeds in the trailing foot onset latency (p = 0.035), step size (p = 0.009), and total number of steps (p = 0.002), while in the females a significant difference was found in peak head yaw velocity between fast and slow turn speeds, and moderate and slow turn speeds. Finally, there was no significant difference in TUG between groups. Therefore, these findings show differences between biological sexes in the response to whole-body coordination and step characteristics, indicating that females tend to have more changes in stepping characteristics compared to males due to differences in turning speed. This can affect their balance and stability. However, the differences in biological sex did not impact the dynamic balance and fall risk due to the lack of a significant difference shown by TUG between males and females.

Quantified the influence of different synoptic weather patterns on the transport and local production processes of O3 events in Pearl River Delta, China

Regional ozone (O3) pollution in the Pearl River Delta (PRD) region has become a topic of discussion in recent years. The occurrence of regional O3 pollution are influenced by local emissions and cross-regional transportation. In this study, we identified the predominant synoptic patterns that were associated with regional O3 pollution from August to November in 2015–2021 using the Lamb-Jenkinson classification technique. All synoptic types were divided into four major categories of NE-type, C-type, S-type and A-type, which accounted for 42 %, 25 %, 18 % and 15 % of the total number of regional O3 pollution days, respectively. The weather conditions for each synoptic pattern were described by using MERRA-2 datasets. Then a rapidly method was established to quantify the contribution of cross-regional processes to high O3 concentration in different synoptic patterns over the PRD through the WRF-Flexpart model. The NE-type weather condition was characterized by a relatively large wind speed with a significant cross-regional transport contribution of 35.8 %. The A-type weather condition had moderate surface wind speed with the stable weather condition, resulting in a lower cross-region transport contribution of 27.7 %. Under controlled by C-type, the stagnant weather condition caused by low-pressure systems on its periphery, would suppress diffusion of O3. As a result, the regional O3 pollution in the PRD were mostly attributed to locally (87.9 %) with minimal cross-regional transport (12.1 %). The S-type weather condition was mainly associated with the West Pacific Subtropical High and the surface equalization pressure field, accompanied by low wind speed. Therefore, the considerable (minor) contribution of local production (cross-regional transport) of 83.3 % (16.7 %) to O3 pollution in the PRD is a consequence of the stagnation weather condition.

The Influence of Meteorological Factors and the Time of Day on the Concentration of Ammonia in the Atmosphere Measured Using the Photoacoustic Method near a Cattle Farm—A Case Study

Influences of animals, time of day, air temperature and relative humidity, wind speed and direction on ammonia concentrations were investigated. A case study on a typical summer day from 7:00 to approximately 24:00 CEST (moderate wind speed, variable cloudiness and maximum global radiation higher than 950 W/m2) in west–central Poland is presented. Concentrations of this gas were measured at four heights (0.1–1.5 m), which were changed every 5 min, using a Nitrolux 1000 photoacoustic spectrometer. A micrometeorological station was established to also measure the surface energy budget components. The results presented are the average for each hour and for the entire day. The fine structure of concentration profiles, plume detection and uncertainty of ammonia flux calculation are also presented. The highest NH3 concentrations were at a 0.5 m height between 16:00 and 17:00 h when cows were grazing, but the lowest concentrations were between 23:00 and 24:00 h at the height of 1.5 m. The ammonia concentration increased with increasing air temperature and was the highest with a westerly wind direction and decreased with increasing air relative humidity. The greatest influence on the ammonia concentration was related to the presence of cows and the time of day, while a slightly smaller influence was noted in terms of air temperature and wind direction. A case study is suitable for presenting local effects, inhomogeneities and quantifying uncertainties in the bidirectional ammonia flux calculation.

Multi-Site Identification and Generalization of Clusters of Walking Behaviors in Individuals With Chronic Stroke and Neurotypical Controls

Background Walking patterns in stroke survivors are highly heterogeneous, which poses a challenge in systematizing treatment prescriptions for walking rehabilitation interventions. Objectives We used bilateral spatiotemporal and force data during walking to create a multi-site research sample to: (1) identify clusters of walking behaviors in people post-stroke and neurotypical controls and (2) determine the generalizability of these walking clusters across different research sites. We hypothesized that participants post-stroke will have different walking impairments resulting in different clusters of walking behaviors, which are also different from control participants. Methods We gathered data from 81 post-stroke participants across 4 research sites and collected data from 31 control participants. Using sparse K-means clustering, we identified walking clusters based on 17 spatiotemporal and force variables. We analyzed the biomechanical features within each cluster to characterize cluster-specific walking behaviors. We also assessed the generalizability of the clusters using a leave-one-out approach. Results We identified 4 stroke clusters: a fast and asymmetric cluster, a moderate speed and asymmetric cluster, a slow cluster with frontal plane force asymmetries, and a slow and symmetric cluster. We also identified a moderate speed and symmetric gait cluster composed of controls and participants post-stroke. The moderate speed and asymmetric stroke cluster did not generalize across sites. Conclusions Although post-stroke walking patterns are heterogenous, these patterns can be systematically classified into distinct clusters based on spatiotemporal and force data. Future interventions could target the key features that characterize each cluster to increase the efficacy of interventions to improve mobility in people post-stroke.