Speed Drop Research Articles

The evaluation of dripping behaviors during the manufacturing process based on image processing method: Application to the Ginkgo biloba leaf dripping pills

The aim of this paper was to investigate the droplet morphology and evaluate the dripping behaviors during the dripping process based on image processing technology. An image acquisition system, which consisted of an industrial camera and a light source, was established. Four indexes including the area, the shape aspect ratio of the droplet, the shape parameter and the contact angle of the droplet images were studied to characterize the droplet morphology. The algorithms for calculating the image indexes and grouping the dripping cycles were designed. The relationships between the droplet morphology and the dripping behavior were conducted, such as the drop speed and the dripping pill weight. The method was well applied to Ginkgo biloba leaf dripping pills. The result showed that the variation trends of the area, the shape aspect ratio of the droplet and the contact angle could effectively characterize the droplet morphology and represent the dripping pill weight fluctuation.

A Liquid drop Falling in Another Fluid: A Two-Phase Flow Phenomenon

Liquid drops exist everywhere in daily life. However, such a common phenomenon involves complex mechanisms, and therefore has never been investigated thoroughly—the achievements of the studies are limited and unsatisfactory. In this article, the phenomenon of a liquid drop falling in another immiscible fluid (mostly its settling speed) was investigated. A series of experiments, in which liquid drops emerging from a syringe falls inside a measuring cylinder filled another fluid, was performed. Fluids used in the experiment include ethanol solutions and rice bran oil; for rice bran oil, its temperature-dependent viscosity was approximated by a function, which was proved effective on other similar oils. The dependence of the settling speed of the liquid drop on the density difference between the liquid drop and the surrounding fluid, as well as on the temperature of the surrounding fluid, was measured. Finite-Element Modeling (FEM) simulations were then carried out to model these situations, and lead to results that agreed with the experiments. It also visualized the flow field and revealed more details of the two-phase flow that were not detectable by our devices. Furthermore, inspired by some previous formulae, quantitative equations were derived semi-analytically by modifying an approximate drag formula originally developed for a rigid object at moderate Reynolds numbers. The form of the modification was never introduced in any other previous works. The equations were validated by simulations under ideal conditions.

Tool Evaluation & Design Analysis for Parking Pawl Mechanism

Abstract: Automatic Transmissions in vehicles are becoming the norm today and with the need to reduce fuel consumption, electric vehicles are increasing in number too. As the vehicles get smarter, transmissions have also felt the need to adapt so as to cope with the demands of the 21st century. Apart from providing the user with different driving modes, vehicles with an Automatic Transmission and electric vehicles have a device called a Park Lock. Park Lock Mechanisms are devices that are fitted to vehicles with an automatic transmission or electric vehicles which can secure the vehicle mechanically in addition to the parking brakes to prevent an unintended movement of the vehicle when the vehicle is brought to a stop. This system can face various kinds of loads coming from the transmission or from the wheel side. So, it is necessary to design a system which can withstand against it. Today, when a park lock mechanism is designed, it is designed in a way that it not only fits one vehicle variant but many variants (these variants can include either front wheel drive, rear wheel drive, vehicles with varying final gear to park lock gear ratios etc). Therefore, one Park Lock Mechanism needs to satisfy various conditions and requirements. Carrying out calculations with different notations for each variant becomes a cumbersome procedure, therefore it is prudent to have one common platform which can do the calculation in the early phases of design. In this paper, a closed form calculationsbased Excel VBA tool can able to estimate the loads coming on to the Park lock mechanism by doing some background calculation is presented followed by the simulation performed using Multi Body Dynamics software (‘ADAMS’). Results from MBD tool and a 1D tool are corelated to the test data to gain some confidence on the tool which created in Excel VBA. Keywords: Park Lock Mechanism, ADAMS, 1D Tool, Excel VBA, Drop in Speed, Torque Build up.

Performance Analysis of Road Intersections under Heterogeneous Traffic Conditions: A Review

The rapid growth of traffic in most countries exceeds the current transport system's threshold level and requires a more efficient and practical approach to be addressed. As the renovation of urban transportation infrastructure is not feasible, alternatives to the problem are urgently needed. This paper addresses the Performance Analysis of Road Intersections under Heterogeneous Traffic Conditions. At whatever point two or significantly more streets converge or cross, users of these streets should change their mobility to prevent a collision. This adjustment can take the form of a speed drop or a change in their motion pattern. In several regions of the world, traffic is a mixture of large distribution of various vehicle kinds. Hence users of a signalized crossroads in vehicles are a heterogeneous mix. The current study has involves review based on 5 selected papers analysing findings and drawing conclusion along with posing future questions.

Multistage Impacts of the Heavy Rain Process on the Travel Speeds of Urban Roads

Heavy rain causes the highest drop in travel speeds compared with light and moderate rain because it can easily induce flooding on road surfaces, which can continue to hinder urban transportation even after the rainfall is over. However, very few studies have specialized in researching the multistage impacts of the heavy rain process on urban roads, and the cumulative effects of heavy rain in road networks are often overlooked. In this study, the heavy rain process is divided into three consecutive stages, i.e., prepeak, peak, and postpeak. The impact of heavy rain on a road is represented by a three-dimensional traffic speed change ratio vector. Then, the k-means clustering method is implemented to reveal the distinct patterns of speed change ratio vectors. Finally, the characteristics of the links in each cluster are analyzed. An empirical study of Shenzhen, China suggests that there are three major impact patterns in links. The differences among links associated with the three impact patterns are related to the road category, travel speeds in no rain days, and the number of transportation facilities. The findings in this research can contribute to a more in-depth understanding of the relationship between the heavy rain process and the travel speeds of urban roads and provide valuable information for traffic management and personal travel in heavy rain weather.

Wave energy harvesting impulse turbine having ring type blade: Experiments with unsteady flow

Oscillating water column (OWC) wave energy converters employ air turbines coupled with an electrical generator to convert the wave energy into electrical energy. In the present study, a ring-type axial flow impulse turbine of diameter 196 mm was manufactured to carry out the experiments in an unsteady flow test rig. The tests were done for the stroke lengths (SL) of 0.2m, 0.3m, and 0.4m, and the periods (TP) varied from 6 to 12 s. A rheostat was connected to the generator, and the turbine pressure drop and power output variations were recorded for different generator loading conditions. The flow rates for the exhalation phase were measured and time-series analysis of the pressure drop and rotor speed was done. A suitable resistive load was found out for obtaining the highest power output. A relationship between average power and average pressure drop was established. Furthermore, a relationship was established between the turbine pressure coefficient and the turbine power coefficient. Lastly, a study on damping characteristics of the turbine was also done to study the effect of damping on the turbine's overall performance.

Modified PDMS with inserted hydrophilic particles for water harvesting

Invisible water is viewed as a potential resource for plants grown in deserts. Amphiphilic surfaces with good flexibility and coalescence are desired for water harvesting applications, but they cannot be precisely controlled. Inspired by desert beetles, we present an amphiphilic surface array that can rapidly condense and slide water droplets. The surface consists of a hydrophilic particle array inserted on a hydrophobic substrate of PDMS mixed with graphene powder. SEM images showed that Fe-particles with different dimensions inserted on an amphiphilic surface enabled the formation of hydrophilic islands. The rapid dropping frequency and landing speed tiny drops were due to the presence of more hydrophobic spaces between single hydrophilic spots and the suitable size of hydrophilic spots. We further demonstrated that the Amphiphilic-15 surfaces, due to its suitable hydrophilic spots size matching with favorable hydrophobic space, outperforms hydrophobic, hydrophilic, and other surfaces during water harvesting.

Optimal observer‐based output feedback controller for traffic congestion with bottleneck

AbstractThis article designs an optimal observer‐based output feedback control for traffic breakdown to dissolve traffic congestion using the backstepping method and optimization. The linearized Aw–Rascle–Zhang model is used to represent the congested traffic dynamics resulting from traffic breakdown. Based on the factors leading to traffic breakdown, we take into account the boundary conditions consisting of a boundary with a constant density and a speed drop at the upstream inlet of a bottleneck, and a boundary with a disturbance of inflow (high traffic demand) at the inlet of the road segment under consideration. To dissolve traffic congestion, a dynamic feedback controller is designed at the upstream boundary. By using the backstepping approach, an observer‐based output feedback controller is computed to guarantee the integral input‐to‐state stability of the closed‐loop system. By establishing an optimization problem and solving it, the optimal value of the considered class controller is obtained. The performance of the output feedback controller is also validated by numerical simulations.

Problems of selecting filter partition in passenger car engine intake air filters

The aim of this study was to verify the criteria for selecting pleated filter partitions used in passenger car engine filters. The paper presents the problem of optimizing pleated air filters in the dir ection of minimizing pressure drop, which is the source of engine energy losses. Two criteria for selection of a paper filter partition for specific operating conditions of the filter and the engine are presented: criterion of permissible separation speed and criterion of permissible pressure drop. The actual filtration area of 44 paper pleated filter elements used in passenger cars and the air stream flowing through the filter were determined, which made it possible to calculate separation speed. In 62% of the analyzed filter inserts, the calculated separation speeds are within the speed range recommended by the constructors, Fmax = 0,06-0,12 m/s. Exceeding permissible separation speed Fmax = 0,12 m/s was found mainly in supercharged engines. Negative effects of engine operation with an air filter with too small separation area are presented, in the form of increased pressure drop and energy loss of the engine as well as shorter car mileage to reach permissible pressure drop.

Imbalance‐based primary frequency control for converter‐fed microgrid

Frequency droop control is a simple and effective frequency control method. However, it is not appropriate as a primary frequency control for microgrids with energy storage systems and voltage source converters (VSCs) owing to their slow response speed. In addition, it is difficult to determine the grid balance only with frequency deviation. In this paper, a new converter-fed microgrid primary frequency control method based on the estimated active power imbalance for fast response and less variability in the transmission system is proposed. The active power imbalance is estimated via frequency deviation, frequency drop speed and the modified swing equation. The estimated imbalance indicates the status of the power imbalance more quickly and accurately than the frequency deviation. The proposed method does not require communication devices, responds quickly to frequency drops, and prevents unnecessary operation of the grid-connected VSC because it uses the estimated imbalance instead of the frequency or angle for droop control. Simulation results show that the proposed method is significantly faster than frequency droop control methods, improves the rate of change of frequency and frequency nadir and reduces variability in the transmission system.

An approach to improve SSD through mask prediction of multi-scale feature maps

We propose a novel single shot object detection network with a mask prediction branch. Our motivation is to enhance object detection features with semantic information extracted from deeper layers. The proposed mask prediction branch enriches important features in shallower layers with pixel-wise probability distribution of semantic information. Meanwhile, an improved receptive field block is adopted to increase the scale of receptive field of backbone network without too much extra computing burden. Our network improves the performance significantly over SSD and FSSD (Feature Fusion Single Shot Multi-box Detector) with just a little speed drop. In addition, we discuss the relationship between effective receptive fields and theoretical receptive fields on VGG16 backbone network. Comprehensive experimental results on PASCAL VOC 2007 demonstrate the effectiveness of the proposed method. We achieve a mAP of 79.8 with 300 × 300 input images (81.2 mAP by 512 × 512 inputs) at the speed of 58.4 FPS on a single Nvidia 1080Ti GPU. Experimental results demonstrate that the proposed network achieves a comparable performance with the state-of-the-arts.

Crack Propagation in the Tibia Bone within Total Knee Replacement Using the eXtended Finite Element Method

Understanding of fracture mechanics of the human knee structures within total knee replacement (TKR) allows a better decision support for bone fracture prevention. Numerous studies addressed these complex injuries involving the femur bones but the full macro-crack propagation from crack initiation to final failure and age-related effects on the tibia bone were not extensively studied. The present study aimed to develop a patient-specific model of the human tibia bone and the associated TKR implant, to study fatigue and fracture behaviors under physiological and pathological (i.e., age-related effect) conditions. Computed tomography (CT) data were used to develop a patient-specific computational model of the human tibia bone (cortical and cancellous) and associated implants. First, segmentation and 3D-reconstruction of the geometrical models of the tibia and implant were performed. Then, meshes were generated. The locations of crack initiation were identified using the clinical observation and the fatigue crack initiation model. Then, the propagation of the crack in the bone until final failure was investigated using the eXtended finite element method (X-FEM). Finally, the obtained outcomes were analyzed and evaluated to investigate the age-effects on the crack propagation behaviors of the bone. For fatigue crack initiation analysis, the stress amplitude–life S–N curve witnessed a decrease with increasing age. The maximal stress concentration caused by cyclic loading resulted in the weakening of the tibia bone under TKR. For fatigue crack propagation analysis, regarding simulation with the implant, the stress intensity factorand the energy release rate tended to decrease, as compared to the tibia model without the implant, from 0.152.5 to 0.111.9 (MPa) and from 10240 to 5133 (J), respectively. This led to the drop in crack propagation speed. This study provided, for the first time, a detailed view on the full crack path from crack initiation to final failure of the tibia bone within the TKR implant. The obtained outcomes also suggested that age (i.e., bone strength) also plays an important role in tibia crack and bone fracture. In perspective, patient-specific bone properties and dynamic loadings (e.g., during walking or running) are incorporated to provide objective and quantitative indicators for crack and fracture prevention, during daily activities.

Risk Factors and Predictors of Hypothermia and Dropouts During Open-Water Swimming Competitions

To measure core temperature (Tcore) in open-water (OW) swimmers during a 25-km competition and identify the predictors of Tcore drop and hypothermia-related dropouts. Twenty-four national- and international-level OW swimmers participated in the study. Participants completed a personal questionnaire and a body fat/muscle mass assessment before the race. The average speed was calculated on each lap over a 2500-m course. Tcore was continuously recorded via an ingestible temperature sensor (e-Celsius, BodyCap). Hypothermia-related dropouts (H group) were compared with finishers (nH group). Average prerace Tcore was 37.5°C (0.3°C) (N = 21). 7 participants dropped out due to hypothermia (H, n = 7) with a mean Tcore at dropout of 35.3°C (1.5°C). Multiple logistic regression analysis found that body fat percentage and initial Tcore were associated with hypothermia (G2 = 17.26, P < .001). Early Tcore drop ≤37.1°C at 2500 m was associated with a greater rate of hypothermia-related dropouts (71.4% vs 14.3%, P = .017). Multiple linear regression found that body fat percentage and previous participation were associated with Tcore drop (F = 4.95, P = .019). There was a positive correlation between the decrease in speed and Tcore drop (r = .462, P < .001). During an OW 25-km competition at 20°C to 21°C, lower initial Tcore and lower body fat, as well as premature Tcore drop, were associated with an increased risk of hypothermia-related dropout. Lower body fat and no previous participation, as well as decrease in swimming speed, were associated with Tcore drop.

Bench Testing and Modeling Analysis of Optimum Shifting Point of HMCVT

The unreasonable shift point will cause a large shift impact, which will affect the engine fuel economy and the service life of the wet clutch. To decrease shift impact on agricultural tractors with HMCVT (Hydromechanical Continuously Variable Transmission) and find the best working point, the following methods are proposed in this paper: firstly, conducting all-factor method and response surface method (RSM) to design and carry out bench test of shift impact; secondly, using the basic linear fitting, RSM, and stepwise regression analysis to establish comprehensive mathematical models and selecting models with high prediction accuracy; thirdly, putting forward the method of determining the weight of variance to match parameters of three quality evaluation indexes with inconsistent correlation; finally, establishing the total shift quality evaluation index and obtaining the optimal shift working point. It is found that oil filling pressure has a significant effect on speed drop, while the engine speed has a significance on the dynamic load and sliding friction. To make the transmission section of the best quality, the oil pressure at this time is 1 MPa and the engine speed is 1040 r/min. The results show that the proposed method can determine the optimal shift point and provide a reference for developing the control strategy.

The Effect of Thermal Pressure on Collisionless Magnetic Reconnection Rate

Abstract Modeling collisionless magnetic reconnection rate is an outstanding challenge in basic plasma physics research. While the seemingly universal rate of an order is often reported in the low-β regime, it is not clear how reconnection rate scales with a higher plasma β. Due to the complexity of the pressure tensor, the available reconnection rate model is limited to the low plasma-β regime, where the thermal pressure is arguably negligible. However, the thermal pressure effect becomes important when . Using first-principle kinetic simulations, we show that both the reconnection rate and outflow speed drop as β gets larger. A simple analytical framework is derived to take account of the self-generated pressure anisotropy and pressure gradient in the force balance around the diffusion region, explaining the varying trend of key quantities and reconnection rates in these simulations with different β. The predicted scaling of the normalized reconnection rate is in the high-β limit, where β i0 is the ion β of the inflow plasma.

Video object detection with a convolutional regression tracker

Video object detection is a fundamental research task for scene understanding. Compared with object detection in images, object detection in videos has been less researched due to shortage of labelled video datasets. As frames in a video clip are highly correlated, a larger quantity of video labels are needed to have good data variation, which are not always available as the labels are much more expensive to attain. Regarding the above-mentioned problem, it is easy to train an image object detector, but not always possible to train a video object detector if there are insufficient video labels for certain classes. In order to deal with this problem and improve the performance of an image object detector for the classes without video labels, we propose to augment a well-trained image object detector with an efficient and effective class-agnostic convolutional regression tracker for the video object detection task. The tracker learns to track objects by reusing the features from the image object detector, which is a light-weighted increment to the detector, with only a slight speed drop for the video object detection task. The performance of our model is evaluated on the large-scale ImageNet VID dataset. Our strategy improves the mean average precision (mAP) score for the image object detector by around 5% and around 3% for the image object detector plus Seq-NMS post-processing.

Analysis of Motility Patterns of Stentor During and After Oral Apparatus Regeneration Using Cell Tracking.

Stentor coeruleus is a well-known model organism for the study of unicellular regeneration. Transcriptomic analysis of individual cells revealed hundreds of genes-many not associated with the oral apparatus (OA)-that are differentially regulated in phases throughout the regeneration process. It was hypothesized that this systemic reorganization and mobilization of cellular resources towards growth of a new OA will lead to observable changes in movement and behavior corresponding in time to the phases of differential gene expression. However, the morphological complexity of S. coeruleus necessitated the development of an assay to capture the statistics and timescale. A custom script was used to track cells in short videos, and statistics were compiled over a large population (N ~100). Upon loss of the OA, S. coeruleus initially loses the ability for directed motion; then starting at ~4 h, it exhibits a significant drop in speed until ~8 h. This assay provides a useful tool for the screening of motility phenotypes and can be adapted for the investigation of other organisms.

Spatial variations of North Atlantic landfalling tropical cyclone wind speed decay over the continental United States

AbstractUnderstanding tropical cyclone wind speed decay during the post-landfall stage is critical for inland hazard preparation. This paper examines the spatial variation of wind speed decay of tropical cyclones over the continental United States. We find that tropical cyclones making landfall over the Gulf Coast decay faster within the first 24 hours after landfall than those making landfall over the Atlantic East Coast. The variation of the decay rate over the Gulf Coast remains larger than that over the Atlantic East Coast for tropical cyclones that had made landfall more than 24 hours prior. Besides an average weaker tropical cyclone landfall intensity, the near-parallel trajectory and the proximity of storms to the coastline also help to explain the slower post-landfall wind speed decay for Atlantic East Coast landfalling tropical cyclones. Tropical cyclones crossing the Florida peninsula only slowly weaken after landfall, with an average of less than 20% post-landfall wind speed drop while transiting the state. The existence of these spatial variations also brings into question the utility of a uniform wind decay model. While weak intensity decay over the Florida peninsula is well estimated by the uniform wind decay model, the error from the uniform wind decay model increases with tropical cyclones making direct landfall more parallel to the Atlantic East Coast. The underestimation of inland wind speed by the uniform wind decay model found over the western Gulf Coast brings attention to the role of land-air interactions in the decay of inland tropical cyclones.

Water transport performance of inhomgenous nanoconfined systems

Graphene nanochannels have attracted extensive attention in the fields of physics, biology, mechanics and materials due to their super long slip length and unique fluid transport properties. Up to now, research on confined liquid transport of carbon-based materials relies primarily on homogeneous nanoconfinement. Here, we investigate the transport behavior of confined water between inhomogeneous graphene channels by means of molecular dynamics simulations. Our results show that the confined water in the channel transforms into different lamellar structures in different areas. With the increase of water density, the water structure will gradually change from liquid to regular square-like solid. Besides, the speed of water decreases first, then increases and then decreases again with the increase of water density. This is because under low density (0.8–0.9 g/cm3), the interface friction increases with the increase of density, causing the speed of water to decrease. When the density reaches phase transition density (1.0 g/cm3), the friction coefficient will reduce sharply. With the continuing increase of density (1.0–1.4 g/cm3), interface friction increases, leading to speed drop of water again. Our results provide theoretical support for understanding the phase state and transport characteristics of water in confined systems, and have some guiding significance for material transport in biological channels and seawater desalination.

Research on Torque Control Distribution between Motor and Engine in P2.5 Hybrid Vehicle

The normal torque distribution of the P2.5 hybrid system is based on the strategy of open-loop engine control, dynamic engine torque estimation and the motor torque compensation. To meet the rapid acceleration and the deceleration, the motor torque is compensated according to the estimated engine torque to satisfy the driver torque request first, and then satisfy the battery charge torque. Other torque distribution strategies are defined according to the special working conditions below:1) To improve the efficiency of the engine and the response of the system and to avoid the drop of engine speed, the motor compensation enabled condition and torque distribution strategy is defined.2) To enhance the performance of fuel consumption and emission during the catalyst heat phase, the catalyst heat phase is divided into two phases and the torque distribution strategy is defined. 3) To decrease the battery heat time and extend the battery health life, the battery heat enabled condition and torque distribution are defined. The vehicle results are conducted and show that the normal torque distribution control can meet the acceleration and deceleration goal and drivability performance. The motor compensation can meet the driver torque by the motor and avoid the drop of the engine speed. The control of the catalyst heat phase can do good to the emission and fuel consumption.