Optimal Velocity Research Articles

Interactions between fluorocarbon surfactant and coal dust at macro, meso and molecular scales and their applications in coal dust control

Surfactants play an important role in the field of coal dust prevention, among which fluorocarbon surfactants have the advantages of low surface tension and have the potential to become mine dust suppressants. In this study, the wettability of fluorocarbon surfactant (OBS) on coal dust was studied from macro experiments, meso dust mist coupling and micro molecular simulation. The results showed that the surface tension of 0.06% OBS was as low as 17.6 mN/m, and the median particle size of coal dust reached 60.25 μm after wetting coal dust. Coal dust particles are easier to bond with each other into large particles, thus promoting settlement; During the meso collision between droplets and coal dust particles, OBS droplets showed excellent wetting and spreading effect, and the droplet state was stable, and the optimal spraying velocity was determined to be 20–30 m/s; At the molecular level, the diffusion coefficient of water molecules in the OBS system is minimally 0.46 Å2/ps, indicating a strong ability to constrain water molecules. The strength and energy of the hydrogen bonds formed with water molecules were greater than those of hydrocarbon surfactants, resulting in the best adsorption of water molecules. Additionally, it was found that the law of attractive and competitive adsorption of different surfactants in wetting coal dust is based on the difference in positive and negative electrostatic potential, where the greater the difference, the stronger the interaction. This provides a theoretical reference for judging the wetting performance of different surfactants at the molecular level.

On-Chip Comparison of the Performance of First- and Second-Generation Micropillar Array Columns.

Because of its dimensions, the recently introduced micropillar array columns are most suited for high-efficiency liquid chromatography separations in proteomics. Unlike the packed bed columns and capillary-based column formats, the micropillar array concept still has significant room to progress in terms of the reduction of its characteristic size (i.e., pillar diameter and interpillar distance) to open the road to even higher-efficiency separations and their applications. We report here on the on-chip comparison between first-generation (Gen 1) and second-generation (Gen 2) micropillar array columns wherein the pillar and interpillar size have been halved. Because of the on-chip measurements, the observed plate heights H represent the fundamental band broadening, devoid of any extra-column band-broadening effects. The observed reduction of H with a factor of 2 around the uopt-velocity and with a factor of 4 in the C-term dominated regime of the van Deemter-curve is in full agreement with the theoretically expected gain. This shows the pillar and interpillar size reduction could be effectuated without affecting the theoretical separation potential of the micropillar arrays. Compared to Gen 1, Gen 2 offers a 4-fold reduction of the required analysis time around the optimal velocity and about a 16-fold reduction in the C-term-dominated range.

Experimental study on the influence of inlet velocity and fuel/air ratio on outlet temperature profile performance in a turboshaft engine combustor

This paper presents an experimental study on the influence of inlet velocity and fuel/air ratio (FAR) on the outlet temperature profile in a mixed-flow trapped vortex combustor (MTVC) working with RP-3 liquid fuel. This new MTVC is using a single cavity to stabilize flames for turboshaft engine. Temperature profile performances, such as temperature non-uniformity, radial temperature profile, profile factor (RTDF) and pattern factor (OTDF), were examined at atmospheric pressure on a fan-shaped test rig at different inlet velocities and fuel/air ratios. By analyzing the temperature pattern in the cavity, the reason for the characteristic law of the outlet temperature profile is obtained. The results indicate that the MTVC has achieved a satisfactory temperature profile, which can meet the requirements of the turbine. The radial temperature profile at combustor outlet is not a flat straight line, showing a pattern of high temperature in the middle of combustor outlet and low temperature at both ends of combustor outlet. The peak temperature is 0.6 times the height of combustor outlet. The high temperature zone with a constant FAR lean towards the top of the outlet center, and the temperature non-uniformity, OTDF and RTDF increase with increasing velocity. However, the high temperature zone approaches the outlet axis at a constant velocity as FAR changes. The temperature non-uniformity decreases with an increases of FAR. There is an optimal velocity where OTDF and RTDF pass through a minimum value. A decrease or increase in velocity beyond this optimal velocity results in an increase in both OTDF and RTDF. This mainly depends on the fuel distribution, the air jet mixing, the local FAR in cavity, and the location of high-temperature products in combustor outlet.

The Application of Barocaloric Solid-State Cooling in the Cold Food Chain for Carbon Footprint Reduction

In this paper, the application of solid-state cooling based on the barocaloric effect in the cold food supply chain is investigated. Barocaloric solid-state technology is applied to the final links of the cold food supply chain regarding the steps of retail and domestic conservation. In this context, effective barocaloric cooling entails the refrigeration of food at 5 °C (273 K) and as such is a promising cooling technology due to its energy efficiency and environmental friendliness. The categories of food involved in this investigation are meat and fresh food products like soft cheese, yogurt, and milk. The energy performance of the barocaloric system is analyzed and compared with a commercial vapor compression refrigerator of a similar size, both operating using R600a under the same working conditions. Based on the results of this comparison, it is concluded that barocaloric cooling is a favorable technology for application in the final links of the cold food supply chain if the system operates in an ABR cycle at frequencies between 1.25 and 1.50 Hz with a regenerator comprising acetoxy silicone rubber as the solid-state refrigerant and a 50%EG–50% water mixture as the heat transfer fluid flowing at an optimal velocity of 0.15 m s−1. Thus, an appropriate tradeoff between the temperature span, cooling power, and coefficient of performance is guaranteed. Under these conditions, the barocaloric system outperforms the domestic vapor compression cooler operating using R600a.

Impact of driver's advanced reaction time in car-following model with optimal velocity deviation under V2X environment

The vehicle-to-everything (V2X) technology has made a significant advancement in the field of intelligent transportation in recent years. When operating a vehicle in a V2X environment, the driver can get real-time updates on the motion of nearby vehicles. In a real-world traffic situation, there is always some deviation between the actual and anticipated traffic information, and this deviation will undoubtedly have a significant effect on traffic flow. Drivers always maintain the flow of traffic by taking some time to assess and decide how the drivers in front of them are behaving behind the car in the traffic system. As a result, by taking into account the driver's advanced reaction time and optimal deviation in a V2X environment, a novel car-following model is developed and the effects of these parameters on the traffic flow are examined. In order to determine the stability requirements for the new model, the linear and nonlinear stability of the proposed model is examined using the perturbation methods. Studies have found that when the driver's reaction time and the velocity deviation are optimized, it can reduce the amplitude of the stability curve, thus enlarging the area of more stable motion. Also, the numerical simulation supports the theoretical research by showing that the new model may effectively reduce traffic congestion and improve the stability of traffic flow as the influence of these factors on the traffic flow increases.

General Form Equation for the Most Energy-Efficient Basketball Shot

Although ball shooting is one of the fundamental skills of basketball, it is energy intensive and exhausts players quickly. Because of this, effective shooters will have less time to play on the court, which can be the difference between winning and losing for basketball teams. In the National Basketball League (NBA), pride, expectations, and millions of dollars in investments are at stake, making winning all the more critical. Improving basketball shooting accuracy may provide the most robust path forward to increasing team-specific wins. So, to boost shooter performance, we derived an equation that calculates the optimal velocity to shoot a basketball from every position on the court. This ‘optimal’ velocity minimizes a shooter’s energy expenditure so players can conserve their energy and stay effective in the game longer, boosting their team’s chances of winning. We used Newton’s second law and kinematics, vector algebra, and calculus to derive the optimal velocity equation and ultimately implemented it in Python for public use. We concluded that the optimal angle for mid-range shots (3 to 5 meters) is 55 to 51 degrees and 49 to 47 for three-point shots.

Traffic flow study for a modified car-following model based on dynamical safety headway

A modified optimal velocity with dynamical safety headway is introduced based on the optimal velocity car-following model. The dynamical safety headway relates to vehicle’s velocity compared to the constant safety headway. To study the influence of dynamical safety headway on the car-following performance, theoretical analysis and numerical simulation of the optimal velocity car-following model with dynamical safety headway are carried out. With the stability analysis method in control theory, a linear stability condition is obtained for the new model. In addition, the car-following performances of traffic flow evolution rules, traffic capacity properties and vehicle starting features of the new model are exhibited through numerical simulation. The results show that the dynamical safety headway is more efficient than the constant safety headway in improving traffic stability, enhancing traffic capacity and shortening the vehicle starting time in the car-following process. It concludes that the dynamical safety headway is a better strategy compared to constant safety headway in real car-following control.

Optimal coverage control of stationary and moving agents under effective coverage constraints

This paper addresses the problem of maximizing coverage in a mission space with both stationary and mobile agents such that effective coverage constraints are satisfied, i.e., each point of the mission space must be covered to a predefined level at least once over a given time period. The deployment of the stationary agents may be given in advance or may be obtained by a classical coverage control algorithm. The motion planning of the mobile agents is designed under maximal speed and acceleration constraints. When there is only one mobile agent, it is shown that its path planning and velocity planning can be designed separately. We first obtain an optimal velocity policy and the corresponding optimal coverage performance for a given path, which provides a criterion to prescribe a good path. Then, path planning is generated to meet the effective coverage constraint by connecting a set of “inspection points”. Inspired by the optimal velocity policy, we propose three methods to generate the inspection points and obtain the optimal order of connecting the inspection points by a Traveling Salesman Problem (TSP)-based method. Finally, we extend the one-mobile-agent motion planning scheme to multiple mobile agents by proposing two methods. Simulation examples are included to compare the performance of the three methods for generating inspection points and compare the performance of the proposed methods for multiple mobile agents.

A car-following model based on the optimized velocity and its security analysis

Abstract An enhanced optimal velocity model (EOVM) that considers driving safety is established to alleviate traffic congestion and ensure driving safety. Time headway is introduced as a criterion for determining whether the car is safe. When the time headway is less than the minimum time headway (THmin ) or more than the most comfortable time headway (THcom), the acceleration constraints are discussed to ensure the model’s safety and maintain the following state. A stability analysis of the model was carried out to determine the stability conditions of the model. The EOVM is compared with the optimal velocity model (OVM) and fuzzy car-following model using the real dataset. Experiments show that the EOVM model has the smallest error in average, maximum and median with the real dataset. To confirm the model’s safety, design fleet simulation experiments were conducted for three actual scenarios of starting, stopping and uniform process.

Machine-learning a perfect bending soccer goal shot

The objective of this work is to ascertain the optimal bending kick velocity and spin that a player should impart to exactly hit a target within a soccer goal, using machine-learning optimization. Specifically, the work develops a model of a kicking player producing a high-velocity spinning soccer ball which interacts with the surrounding air that induces drag forces and the Magnus effect, both of which are functions of the Reynolds number. This yields a set of highly nonlinear, coupled, differential equations. The framework is designed to enable digital-twin type technologies, i.e. digital replicas that run in real time with the physical system on laptops or other mobile systems for rapid feedback. The overall guiding motivation is to provide a useful tool to assist coaches and to rapidly train players. Numerical examples are provided to illustrate the process.

Trajectory planning approach for autonomous electric bus in dynamic environment

Path planning is a challenging task to achieve vehicle autonomy, and it becomes even more difficult in handling dynamic situations and big vehicle sizes. Its performance is affected by the accuracy of mapping and vehicle localization. Many path planning algorithms have been developed to address static environments, however, these do not accurately reflect real-world scenarios which are dynamic in nature. This paper introduces a new planning architecture consisting of a global planner that plans a path in an occupancy grid map generated using LIDAR and odometry data. The local planner uses this global plan and plans a local plan on a section of the map that takes into consideration dynamic obstacles. Both the local and global plans are used to calculate the optimum velocity profile, providing a feasible and comfortable trajectory. The trajectory is then fed to a predictive Stanley controller, and both the calculated steering angle and the optimum velocity are achieved by low-level controllers. The performance of the proposed architecture was tested on a golf bus in a constrained environment and compared to different manual driving attitudes using a key performance indicator. The results of the proposed architecture show that it has a better KPI, with an average of 37% better than manual driving.

Novel design of thermo-electric air conditioning system integrated with PV panel for electric vehicles: Performance evaluation

Traditional air conditioning may be inappropriate for electric vehicles due to its moving parts noise besides using chlorofluorocarbons that harm the environment. In addition, it consumes a significant portion of the stored energy in batteries, reducing the vehicle's driving range. So, in this paper, a novel design of thermo-electric cooling (TEC) system coupled with a photovoltaic (PV) panel replacing the vehicle roof is studied. This system consists of a sandwich of PV panel outside the vehicle and TEC inside with a heat sink system integrated between them. The air temperature variation in the cabin during the daytime is predicted by solving a complete mathematical transient thermal model of the whole system before and after mounting the cooling system. The air streams through the vehicle moving are exploited to improve the TEC and PV system performance. The system performance is investigated for different cases during the day with and without including the PV output power and for the vehicle parks inside or outside. The results indicate that, for each scenario, the number of used TEC modules influences the system performance where the best number varies between 128 and 98. Coupling the PV panel with the TEC system reduces the daily required energy from batteries by about 19%. Running the TEC system during parking from 8 to 10 am decreases the cabin air temperature from 47.5 to 34°C while the input power declines by about 45%, which reduces the interior temperature to 25°C in 10 min (transition time). The contribution of the PV panel based on the studied conditions can increase the range of the vehicle by 10.4 km/day and about 160kWh/year energy saving. The reduction in the input power during transition time reaches 27.8% when the vehicle speed increases from 30 to 60 km/h, while this ratio declines to 10.8% as the vehicle speed rises from 60 to 90 km/h. During vehicle moving, powering the TEC system by the PV panel only can prevent the cabin temperature from rising over 40°C, whereas during parking, there is an optimum fan air velocity that gives the maximum reduction of the cabin temperature.

Simultaneous determination and distribution analysis of eleven arsenic species in vegetables

A highly sensitive and efficient method for simultaneous determination of arsenic species in vegetables has been developed. Eleven arsenic species were separated and detected using high performance ion exchange chromatography-inductively coupled plasma mass spectrometry (HPIEC-ICP-MS). The extraction efficiency and transformation of arsenic species in vegetables was investigated using five extraction methods and eight solvents. An online background removal technique was firstly established to exclude the influence of environmental arsenic. The gradient elution conditions were optimized and the optimal collision gas velocity for mass spectrometry was determined to be 4 mL min−1 to remove interference by 75ArCl. The detection limits for the method were 0.032–0.12 μg kg−1, and the quantitative limits of the method were 0.10–0.39 μg kg−1. In order to confirm the accuracy and practicability of the method, two food matrix-type certified reference materials were analyzed. The types and concentrations of arsenic species in six different kinds of vegetable were analyzed. The proportions of As (III) and As (V), as well as total arsenic concentrations, were significantly different.

Optimal Velocity Distributions in the Design of Supercavitating Hydrofoils

Optimal Velocity Distributions in the Design of Supercavitating Hydrofoils

Restoration of a fish-attracting flow field downstream of a dam based on the swimming ability of endemic fishes: A case study in the upper Yangtze River basin

The construction of fish passage facilities can mitigate the negative effects of dams and other water engineering construction on river connectivity and have a significant positive effect on the conservation of local fish diversity. To attract target fishes into fish passage facilities effectively, the optimal flow velocity range to attract fish must be determined. Three local endemic species of the Mishi Reservoir were considered as the protection targets. However, their swimming abilities remain unclear. Therefore, the induced swimming speed (Uind), critical swimming speed (Ucrit) and burst swimming speed (Uburst) of three fish species were tested. Based on these results, we identified the optimal flow velocity to attract fish, which falls within the range of 0.15–0.51 m/s. A validated three-dimensional hydrodynamic model was used to simulate different schemes. By comparing the flow field simulation results of different schemes, we obtained the optimal measure to restore the flow field, namely, a multiple engineering measure combining increased the fish attraction flow in the fish collection pond and the construction of a spur dike. This study offers a solution for the specific case and enhances the database of swimming characteristics of endemic fish in the upstream reaches of the Yangtze River. It also provides a valuable reference for designing fish-attracting flows and potential measures for restoring flow fields in similar future projects.

Parametric modeling study for blown-dust secondary pollution and optimal ventilation velocity during tunnel construction

Tunnel construction often relies on drilling and blasting. High dust pollution is one of the primary problems of drilling and blasting construction. The level of secondary blown dust pollution caused by ventilation matches that of dust pollution caused by drilling construction. In this study, a critical flow model and blown dust rate model for deposited dust were established via force analysis, which was validated against the test data. The research results showed that the characteristic airflow velocity for blowing dust particles with a 100 μm diameter reached approximately 0.42 m/s for tunnel diameter is 10 m, and the ventilation Re values under smooth and rough conditions were 2.3 × 105 and 1.4 × 105, respectively. Furthermore, when ventilation Re reached 4 × 105, the blown dust pollution rate caused by ventilation under smooth conditions was approximately 1.8 × 10−2 kg/s. If dust particle size is more or less the critical dust particle size, the characteristic airflow velocity was increased. Moreover, the optimal velocity at which the deposited dust does not flow or move during tunnel construction was related to the tunnel size and roughness. For the smooth tunnel with a diameter of 10 m, the optimal ventilation velocity was 3.5 m/s. When the tunnel roughness was increased from 0.005 to 0.5 m, the optimal ventilation velocity decreased from 3.3 to 1.6 m/s. The deposited dust critical flow model and blown dust pollution rate model established in this study provide a sound theoretical basis for selecting the optimal velocity of tunnel ventilation and recognizing the risks of secondary blown dust pollution due to ventilation.

Thermal performance analysis of liquid cooling system with hierarchically thermal conductive skeleton for large-scaled cylindrical battery module in harsh working conditions

Liquid cooling (LC) technology is most widely used in battery thermal management systems. However, for cylindrical battery modules, tailor-made LC components with curved surface and complicated LC structures are required to match the curved surface of the cells. Herein, we design an easily-assembled LC structure by directly embedding thermal conductive silica gel (SG) into a 21.6 V/39Ah cylindrical battery module with thermal conductive plates (TCPs) connected to LC plates (LCPs). This LC strategy avoids the tedious and costly procedure of processing LC components with special specifications, and demonstrates excellent adaptability to battery modules with diversified specifications. By selecting copper plates and flexible SG with 2 wt% expanded graphite as the TCPs and embedding material respectively, a high-efficient thermal conductive skeleton can be constructed, endowing the module center with a greatly reduced thermal resistance of 1.27 × 10−2 m2∙K∙W − 1. In addition, the optimal water inlet velocity and cell distance are determined to be 0.2 m∙s − 1 and 7 mm, respectively. As a result, the maximum temperature (Tmax) and temperature difference (ΔTmax) of the battery module are well maintained within the optimal ranges of 28.9∼41.7 °C and 1.4∼4.7 °C under all working conditions, respectively. Remarkably, even under the harsh working conditions with a 3 C discharge rate under 25, 35 and 40 °C, the Tmax can be controlled below 31.6, 40.3 and 41.7 °C, while the corresponding ΔTmax are only 4.6, 3.8 and 3.8 °C, respectively.

Determination of Optimum Reaction Velocity for Glucose Production from Cassava Starch Using Gluco Amylase Sourced from Rice

In an attempt to produce glucose from locally sourced materials to boost glucose syrup production and other applications, the optimum reaction velocity which enzyme becomes saturated with the substrate was investigated. In this study, cassava starch (substrate) and glucoamylase (enzyme) from rice were sourced and prepared. The time course of the enzyme hydrolysis was studied at pH 5 and temperature of 400C as optimum conditions. The hydrolysis was carried out at various substrate concentrations. The time course of the reaction for glucose production was monitored at 10 minutes interval for a period of one hour. The glucose concentration produced was plotted against reaction time to evaluate the optimum glucose amount and its corresponding substrate concentration. The reaction velocity was then computed. Also, the experimental data were fitted into Michaelis-Menten model using Statistical Package for Social Scientists to compare the yield of glucose. Results showed optimum yield of glucose concentration was 0.253 g DE L-1 achieved with 2.5 and 3.0% w/v substrate concentration at 50 and 40 minutes respectively. Further analysis gave the optimum reaction velocity range of 0.00506 to 0.00625 of g DE per litre-min.  This range when compared with the model equation result (0.0052 to 0.0068 g DE litre-min) is reasonably close; hence the results from this study are valid. Technical evaluation to standardize the reaction velocity with respect to substrate concentration which may be referred to as specific reaction velocity gave 0.00205 ±0.00005 g D per litre-min per substrate concentration %w/v.

Injection parameter design to improve the high-speed gear heat dissipation: CFD simulation and regression orthogonal experiment

A heat dissipation model of high-speed helical gears based on Computational Fluid Dynamics (CFD) is proposed under injection lubrication. Gear heat dissipation is investigated by static and dynamic heat flow coupling. The oil injection lubrication test is designed to measure tooth temperature by an infrared thermal imager. The results show that owing to the gear centrifugal force, the oil splash, and the blocking effect of the high-speed airflow, the average temperature first decreases and then increases, and the temperature difference increases first and then decreases with the increase in injection angle, distance, and velocity. The average temperature and temperature difference are remarkably affected by the injection velocity and distance, respectively. The optimal injection angle, distance, and velocity predicted by the regression orthogonal method are 9.212°, 54.514 mm and 35.561 m/s, respectively. Infrared thermometry experiments show that the optimal injection parameters enhance the gear heat emission by 6.93%. These findings provide support for the heat dissipation study and injection system design for aerospace gears.

Loaded 5 Sit-to-Stand Test to Determine the Force–Velocity Relationship in Older Adults: A Validation Study

Force–velocity profiling (F-v) evaluates muscle function through the identification of maximum force (F0), velocity (V0), power (Pmax) and optimal velocity (Vopt). The purpose of this study was to investigate the validity and feasibility of loaded 5 Sit-to-Stand (5STS) force-velocity profiling compared to the gold standard instruments (isokinetic Dynamometry, ISO) and asses the relationship between the 5STS-derived muscle function indexes with clinical markers of muscle mass and strength. Forty-six older adults (21 females: 63.8 ± 3.9 yrs) performed 5STS (four different weight conditions) and ISO tests (five different velocities). Paired t-tests, regression analyses, and Bland–Altman analysis were conducted. The results showed significant differences in F0, V0, and Vopt (p < 0.001) but no difference in Pmax (p = 0.259) between tests. Only F0 and Pmax were highly correlated between tests (r = 0.71, r = 0.84, respectively). Bland–Altman analysis showed a not significant bias and good precision (p = 0.260, 34 W) only for Pmax. Large to very large correlations (r = 0.53 to 0.81) were found between F0 and Pmax and clinical markers of muscle mass and strength. In conclusion, loaded 5STS profiling could be a feasible, valid, and cost- and time-efficient alternative to ISO for the characterization of clinically relevant markers of muscle function in healthy older adults.