Low Average Speed Research Articles

Swimming Motility Reduces Deposition to Silica Surfaces.

The transport and fate of bacteria in porous media is influenced by physicochemical and biological properties. This study investigated the effect of swimming motility on the attachment of cells to silica surfaces through comprehensive analysis of cell deposition in model porous media. Distinct motilities were quantified for different strains using global and cluster-based statistical analyses of microscopic images taken under no-flow condition. The wild-type, flagellated strain DJ showed strong swimming as a result of the actively swimming subpopulation whose average speed was 25.6 μm/s; the impaired swimming of strain DJ77 was attributed to the lower average speed of 17.4 μm/s in its actively swimming subpopulation; and both the nonflagellated JZ52 and chemically treated DJ cells were nonmotile. The approach and deposition of these bacterial cells were analyzed in porous media setups, including single-collector radial stagnation point flow cells (RSPF) and two-dimensional multiple-collector micromodels under well-defined hydrodynamic conditions. In RSPF experiments, both swimming and nonmotile cells moved with the flow when at a distance ≥20 μm above the collector surface. Closer to the surface, DJ cells showed both horizontal and vertical movement, limiting their contact with the surface, while chemically treated DJ cells moved with the flow to reach the surface. These results explain how wild-type swimming reduces attachment. In agreement, the deposition in micromodels was also lowest for DJ compared with those for DJ77 and JZ52. Wild-type swimming specifically reduced deposition on the upstream surfaces of the micromodel collectors. Conducted under environmentally relevant hydrodynamic conditions, the results suggest that swimming motility is an important characteristic for bacterial deposition and transport in the environment.

Energy and environmental impact of battery electric vehicle range in China

To meet increasingly stringent emission legislation, electric vehicles are expected to offer promising sustainable mobility in the future. However, the driving range of battery electric vehicles (BEVs) is limited as compared with hybrid electric vehicles (HEVs). Additionally, the grid power supply in China is highly dependent on coal-based thermal power generation, which leads to high grid-carbon intensity and increased well-to-tank (WTT) emission for BEVs. Therefore, the tradeoff between electric vehicle driving range and environmental impact has become a critical problem in BEV development in China.In this study, a BEV model is built and validated. The energy consumption and well-to-wheel (WTW) CO2 emission rates of different driving ranges and test cycles are simulated. To determine the impact of driving patterns on BEV energy consumption, the distribution of vehicle energy consumption is analyzed and an analytical model is proposed to generalize the energy consumption of BEVs in standardized driving cycles to real-world driving with only two statistical characteristics: the average and the variance of the speeds. It is found that BEVs have a great advantage in terms of energy saving only at driving cycles with low average speeds and frequent stops. While driving at highway speeds, the energy consumption of BEVs can be very high. With an understanding of driving pattern impact, parameter variation analysis of the BEV WTW CO2 emission rates for different driving ranges is simulated. Simulation results show that the rolling coefficient and battery energy density have a significant impact on driving range, followed by the drag area. However, grid-carbon intensity is more efficient for reducing WTW CO2 emissions. Currently, optimization of the rolling coefficient and drag area is the most viable option for increasing the battery range and decreasing the WTW CO2 emission rate.Finally, to reduce the energy and environmental impact of BEVs in China, short driving ranges (<250km) and low driving speeds (<80km/h) are suggested for current BEVs, and optimization of the vehicle design and reduction of grid-carbon intensity are considered to be the most critical issues for the future application of BEVs.

Climate Monitoring and Formation Mechanism of Smog Pollution in China

Based on environment monitoring data from China Meteorological Administration and Ministry of Environmental Protection of the People's Republic of China, data of atmosphere probing and re-analysis data of NCAR/NCEP, and researches on sources of smog pollution and on smog composition analysis, the paper demonstrates characteristics of China's smog climate and climate change as well as the progress made in climate monitoring in China, explores the constituents of smog aerosol and its pollution sources, analyzes the air quality difference between metropolises and their adjacent small-sized cities and towns, and dissects the formation mechanism behind the recent three major smog pollution incidents from the perspective of air pollution dynamics. The findings of this study include: days with smog in eastern China are on rapid rise especially in 2013; smog pollution in metropolises are significantly much severer than that in adjacent small-sized cities and towns; and the rising smog pollution in China are mainly from motor vehicle exhaust, industrial emission, coal consumption among other factors. Based on the findings above, the study proposes combined principles and measures to eliminate smog pollution by integrating mitigation, joint prevention, and control. Causes of local variations of smog aerosol concentration fall into two categories: internal factors (pollution sources) and external ones (meteorological conditions). Among all external factors, horizontal convey of particulates is a major factor, and persistent smog pollution incidents are closely related to the vertical structure of static and stable atmosphere, wet deposition, and zones with low average wind speed.

“Charge while driving” for electric vehicles: road traffic modeling and energy assessment

The aim of this research study is to present a method for analyzing the performance of the wireless inductive charge-while-driving (CWD) electric vehicles, from both traffic and energy points of view. To accurately quantify the electric power required from an energy supplier for the proper management of the charging system, a traffic simulation model is implemented. This model is based on a mesoscopic approach, and it is applied to a freight distribution scenario. Lane changing and positioning are managed according to a cooperative system among vehicles and supported by advanced driver assistance systems (ADAS). From the energy point of view, the analyses indicate that the traffic may have the following effects on the energy of the system: in a low traffic level scenario, the maximum power that should be supplied for the entire road is simulated at approximately 9 MW; and in a high level traffic scenario with lower average speeds, the maximum power required by the vehicles in the charging lane increases by more than 50 %.

Optimal Sizing of PMSG for Wind Turbine Applications: Methodology and Analysis

This papers describes the methodology to optimal design of the Permanent Magnet Synchronous Generator (PMSG) of wind turbine systems at the low average wind speed. In order to reduce the loss on systems and the robustness of optimal methodology, the authors used the algorithm genetic for optimization process, the method results will be analysis for characterization of control in order of protection and implementation for the wind turbine system with the power of 15- 20 kW at 6m/s average wind speed. To step up the efficiency of optimal methodology, the authors proposed the concept of PMSG for the passive wind turbine systems (without the control MPPT by power electronic inverter) and using the diodes rectifier for the system design and optimization process. Sample simulation results for three optimal Permanent Magnet Synchronous Generators have been presented and discussed for the fundamental issues. 

Spin wave emission in field-driven domain wall motion

A domain wall (DW) in a nanowire can propagate under a longitudinal magnetic field by emitting spin waves (SWs). We numerically investigated the properties of SWs emitted by the DW motion, such as frequency and wave number, and their relation with the DW motion. For a wire with a low transverse anisotropy and in a field above a critical value, a DW emits SWs to both sides (bow and stern), while it oscillates and propagates at a low average speed. For a wire with a high transverse anisotropy and in a weak field, the DW emits mostly stern waves, while the DW distorts itself and the DW center propagates forward like a drill at a relative high speed.

Utility-Scale Wind Turbine Wake Characterization Using Nacelle-Based Long-Range Scanning Lidar

Abstract To facilitate the optimization of turbine spacing at modern wind farms, computational simulations of wake effects must be validated through comparison with full-scale field measurements of wakes from utility-scale turbines operating in the real atmosphere. Scanning remote sensors are particularly well suited for this objective, as they can sample wind fields over large areas at high temporal and spatial resolutions. Although ground-based systems are useful, the vantage point from the nacelle is favorable in that scans can more consistently transect the central part of the wake. To the best of the authors’ knowledge, the work described here represents the first analysis in the published literature of a utility-scale wind turbine wake using nacelle-based long-range scanning lidar. The results presented are of a field experiment conducted in the fall of 2011 at a wind farm in the western United States, quantifying wake attributes such as the velocity deficit, centerline location, and wake width. Notable findings include a high average velocity deficit, decreasing from 60% at a downwind distance x of 1.8 rotor diameters (D) to 40% at x = 6D, resulting from a low average wind speed and therefore a high average turbine thrust coefficient. Moreover, the wake width was measured to expand from 1.5D at x = 1.8D to 2.5D at x = 6D. Both the wake growth rate and the amplitude of wake meandering were observed to be greater for high ambient turbulence intensity and daytime conditions as compared to low turbulence and nocturnal conditions.

Heliostat drive unit design considerations – Site wind load effects on projected fatigue life and safety factor

A parametric analysis shows the importance of various effects on heliostat drive unit life, including wind conditions, angles of attack, size, and endurance limits and how these affect predicted safety factors required in terms of fatigue damage. Endurance limit effects are shown to be critical, including “wear and tear” reductions from field exposure and operation, which significantly reduce remaining life. Low safety factors are shown to pose a risk of achieving 30-year life, especially when site wind conditions are considered. Gusts significantly increase the required safety factor, even if they occur for only 10% of the time. Seasonal wind speed variations are also shown to be important, in that speeds during a 3-month period, typically in the Spring, that are above the annual average require a significantly higher safety factor than the predicted value based on the annual average alone. Sites with low annual average wind speeds are shown to be preferable. Having heliostats fully stowed at lower wind speeds than legacy specifications of 50mph increase life and reduce safety factors required.

Large eddy simulation of wind turbine wake dynamics in the stable boundary layer using the Weather Research and Forecasting Model

Recently, an actuator disk parameterization was implemented in the Weather Research and Forecasting (WRF) Model for large eddy simulation (LES) of wind turbine wakes. To thoroughly verify this model, simulations of various types of turbines and atmospheric conditions must be evaluated against corresponding experimental data. In this work, numerical simulations are compared to nacelle-based scanning lidar measurements taken in stable atmospheric conditions during a field campaign conducted at a wind farm in the western United States. Using several wake characteristics—such as the velocity deficit, centerline location, and wake width—as metrics for model verification, the simulations show good agreement with the observations. Notable results include a high average velocity deficit, decreasing from 73% at a downwind distance x of 1.2 rotor diameters (D) to 25% at x = 6.6D, resulting from a low average wind speed and therefore high average turbine thrust coefficient. Moreover, the wake width expands from 1.4D at x = 1.2D to 2.3D at x = 6.6D. Finally, new features—namely rotor tilt and drag from the nacelle and tower—are added to the existing actuator disk model in WRF-LES. Compared to the rotor, the effect of the tower and nacelle on the flow is relatively small but nevertheless important for an accurate representation of the entire turbine. Adding rotor tilt to the model causes the vertical location of the wake center to shift upward. Continued advancement of the actuator disk model in WRF-LES will help lead to optimized turbine siting and controls at wind farms.

Potential for wind energy generation in Piracicaba, SP, Brazil

Wind power has gained space in Brazil's energy matrix, being a clean source and inexhaustible. Therefore, it becomes important to characterize the wind potential of a given location, for future applications. The main objective of the present study was to estimate the wind energy potential in Piracicaba, SP, Brazil. The wind speed data were collected by an anemometer installed at the Meteorological Station Luiz de Queiroz College of Agriculture, Piracicaba-SP. The wind speed variability was represented by the Weibull frequency distribution, a probability density function of two parameters (k and c). The parameters k and c were used to correlate the Gamma function with the annual average wind speed, the variance and power mean density. A wind profile was made to evaluate the behavior of historical average speeds at higher altitudes measured by anemometer, to estimate the gain in power density. The values of k for all heights were close to 1 which corresponds to a wind regime highly variable, and c values were also low representing a low average speed of the location. The location was characterized as being unfavorable for the application of wind turbines for power generation.

Effect of urban geometry on pedestrian-level wind velocity

The orientation of the streets and the height of continuous buildings cut off summer breezes and the prevailing wind in Izmir, Turkey. Compared with the northern parts of Turkey, the summer period in Izmir is relatively hot, humid and long. Due to the dense urban structure and the expansion of hard surface materials, the temperature in the city centre is higher than this centre's surroundings and this effect is called the urban heat island. Consequently, pedestrian comfort in the city drops dramatically especially in locations where the wind flow is obstructed by buildings. In addition, natural ventilation through the building façades is weakened due to the low average wind speed in the streets. For better outdoor and indoor comfort the citizens in Izmir should benefit from the prevailing wind and summer breezes locally named ‘imbat’ in the sea-land direction. Therefore, the existing situation is examined through the field study in order to understand the natural ventilation potential at the pedestrian level in the selected main streets in Izmir.

Performance Analysis of Coastal Wind Farms in Jiangsu, China

The operational performances of coastal wind farms, located at the east coast of Jiangsu Province of China, are reported in this paper. The result shows that although a rich wind resources predicted in this area, a strong variation of wind resources characteristics are observed between wind farms. Annual averaged wind speeds of five wind farms at hub height range from 4.8 to 6.6 m/s. In addition, the wind shear coefficient shows largely different although they appear to agree with coastal region characteristics. Ru Dong not only has the highest wind shear coefficient but also a largest range of wind shear coefficient variation amplitude. The Capacity Factors of the selected wind farms range from 16% to 27%. Ru Dong shows a lowest Capacity Factor of 16% which may due to the low average wind speed and high wind shear coefficient. On the contrary, Da Feng has a lower Capacity Factor with sensible wind resources indicating either an improved wind turbine technology or an optimized wind farm operational maintenance is needed to increase wind farm efficiency. The result obtained in this paper provides valuable information for future offshore wind farm development in China.

A Survey on Container Processing in Railway Yards

In spite of extraordinary support programs initiated by the European Union and other national authorities, the percentage of overall freight traffic moved by train is in steady decline. This development has occurred because the macroeconomic benefits of rail traffic, such as the relief of overloaded road networks and reduced environmental impacts, are counterbalanced by severe disadvantages from the perspective of the shipper, e.g., low average delivery speed and general lack of reliability. Attracting a higher share of freight traffic on rail requires freight handling in railway yards that is more efficient, which includes technical innovations as well as the development of suitable decision support systems. This paper reviews container processing in railway yards from an operations research perspective and analyzes basic decision problems for the two most important yard types: conventional rail–road and modern rail–rail transshipment yards. Furthermore, we review the relevant literature and identify open research challenges.

Electric Urban Delivery Trucks: Energy Use, Greenhouse Gas Emissions, and Cost-Effectiveness

We compare electric and diesel urban delivery trucks in terms of life-cycle energy consumption, greenhouse gas (GHG) emissions, and total cost of ownership (TCO). The relative benefits of electric trucks depend heavily on vehicle efficiency associated with drive cycle, diesel fuel price, travel demand, electric drive battery replacement and price, electricity generation and transmission efficiency, electric truck recharging infrastructure, and purchase price. For a drive cycle with frequent stops and low average speed such as the New York City Cycle (NYCC), electric trucks emit 42-61% less GHGs and consume 32-54% less energy than diesel trucks, depending upon vehicle efficiency cases. Over an array of possible conditions, the median TCO of electric trucks is 22% less than that of diesel trucks on the NYCC. For a drive cycle with less frequent stops and high average speed such as the City-Suburban Heavy Vehicle Cycle (CSHVC), electric trucks emit 19-43% less GHGs and consume 5-34% less energy, but cost 1% more than diesel counterparts. Considering current and projected U.S. regional electricity generation mixes, for the baseline case, the energy use and GHG emissions ratios of electric to diesel trucks range from 48 to 82% and 25 to 89%, respectively.

The possibility for energy regeneration by electrification in Swedish car driving

The ability to regenerate energy when braking is a valuable advantage of hybrid and fully electric vehicles. How much energy that can be regenerated depends mainly on the car driving and the capacity of the driveline. Detailed studies of possibilities for brake energy regeneration in real world driving are needed to better understand the potential gains of car-electrification since test cycles do not take individual driving or elevation into account. This study has analysed the potential for regeneration in Swedish car driving by applying a model for a normalized vehicle to a highly detailed and representative data set of individual car movements for privately driven cars in Sweden. The share of energy at the wheels used for braking was found to range from 12% to 63%, with an average of 30%. Engine braking could however reduce the amount of recoverable energy to about 16%. On average 42% and 89% of the potentially regenerable energy is available below 10 and 40 kW, respectively. Drivers with lower average speed have in general a higher share of the energy at the wheels potentially available for regeneration. This is however not an important factor to determine the total yearly energy/cost savings. Instead the yearly mileage is shown to be a more relevant indicator on total energy savings from regeneration. The results are compared to the NEDC and WLTP test cycles.

A spatio-temporal analysis of the impact of congestion on traffic safety on major roads in the UK

A spatio-temporal analysis has been conducted aiming to explore the relationship between traffic congestion and road accidents based on the data on the M25 motorway and its surrounding major roads in England during the period 2003–2007. It was hypothesised that increased traffic congestion may be beneficial to road safety as the number of fatal/killed and serious injury (KSI) accidents would be less due to the low average speed when congestion is present. If this is confirmed, then it poses a potential dilemma for transport policy makers. A series of classical count outcome models (random-effects negative binomial models) and spatial models using a full Bayesian hierarchical approach have been developed in this study in order to examine whether congestion has any effect on the frequency of accidents. The results suggest that increased traffic congestion is associated with more KSI accidents and traffic congestion has little impact on slight injury accidents. This may be due to the higher speed variance among vehicles within and between lanes and erratic driving behaviour in the presence of congestion. In addition, traffic speeds even within congested situations are likely to be relatively high on major roads compared to other parts of the road network. Certain strategies are then proposed to optimise traffic flow which would be beneficial to both congestion and accident reduction.

Driver distraction and performance effects of highway logo sign design

Driver distraction and safety concerns have been identified for new highway logo sign configurations. This study assessed driver perception of logo signs and distraction under nine-panel, overflow-combination, or standard six-panel formats. A nine-panel sign has nine business panels within a single sign; a six-panel sign has six panels within a sign; an overflow-combination consists of a standard six-panel sign and a six-panel sign displaying two different services (e.g., food and gas). In this study, twenty-four participants searched for target food business logos while driving in a high-fidelity driving simulation under each signage condition. Gas and lodging signs were also displayed along the road in conventional six-panel formats. Dependent variables included signal detection, visual attention allocation, and vehicle control measures. Experiment results showed nine-panel signs drew greater visual attention and produced lower average speed than overflow-combination signs, and produced a lower speeding percentage compared to six-panel signs. However, there was no evidence the new configurations (nine-panel and overflow) caused substantive performance changes with safety implications. This study suggested the use of nine-panel and overflow-combination logo signs may be suitable for interchanges where there are more than six qualifying businesses in a category in terms of driver performance and safety.

Study on Shift Schedule of Pure Electric Vehicles Automatic Transmission

This paper puts forward a research design method of pure electric vehicle automatic transmission shift schedule based on the urban road conditions in connection with the problems of the low average speed, the high percentage of idle, and frequently shifting in pure electric vehicle. In order to improve the performance of pure electric vehicle automatic transmission and the using efficiency of the motor, this paper formulates a fuzzy shift schedule in the view of the economy. At the same time, this paper supplies a vehicle simulation in the view of economy through a application instance and the MATLAB / SIMULINK / ADVISOR software. The simulation results show that the fuzzy shift strategy can meet the requirements of the economy very well.

Convergence in a quasilinear parabolic equation with time almost periodic boundary conditions

Consider the problem ut=a(ux)uxx+f(ux)(|x|<1,t>0),ux(±1,t)=±g(t)(t>0), where g(t) is an almost periodic function. We prove the following convergence results. If a time-global solution u is bounded, then it converges to an almost periodic solution which is unique up to space shift, stable and asymptotically stable; if u goes to infinity with positive lower average speed, then it converges to an almost periodic traveling wave which is unique up to space shift, stable, asymptotically stable and has positive average speed.

Dopamine Signaling Is Essential for Precise Rates of Locomotion by C. elegans

Dopamine is an important neuromodulator in both vertebrates and invertebrates. We have found that reduced dopamine signaling can cause a distinct abnormality in the behavior of the nematode C. elegans, which has only eight dopaminergic neurons. Using an automated particle-tracking system for the analysis of C. elegans locomotion, we observed that individual wild-type animals made small adjustments to their speed to maintain constant rates of locomotion. By contrast, individual mutant animals defective in the synthesis of dopamine made larger adjustments to their speeds, resulting in large fluctuations in their rates of locomotion. Mutants defective in dopamine signaling also frequently exhibited both abnormally high and abnormally low average speeds. The ability to make small adjustments to speed was restored to these mutants by treatment with dopamine. These behaviors depended on the D2-like dopamine receptor DOP-3 and the G-protein subunit GOA-1. We suggest that C. elegans and other animals, including humans, might share mechanisms by which dopamine restricts motor activity levels and coordinates movement.