Acceleration Events Research Articles

Creating a driving profile for older adults using GPS devices and naturalistic driving methodology.

Background/Objectives: Road tests and driving simulators are most commonly used in research studies and clinical evaluations of older drivers. We adapted an existing, commercial, off-the-shelf, in-vehicle device for naturalistic, longitudinal research to better understand daily driving behavior in older drivers. Design: The Azuga G2 Tracking Device TM was installed in each participant's vehicle, and we collected data over 5 months (speed, latitude/longitude) every 30-seconds when the vehicle was driven. Setting: The Knight Alzheimer's Disease Research Center at Washington University School of Medicine. Participants: Five individuals enrolled in a larger, longitudinal study assessing preclinical Alzheimer disease and driving performance. Participants were aged 65+ years and had normal cognition. Measurements: Spatial components included Primary Location(s), Driving Areas, Mean Centers and Unique Destinations. Temporal components included number of trips taken during different times of the day. Behavioral components included number of hard braking, speeding and sudden acceleration events. Methods: Individual 30-second observations, each comprising one breadcrumb, and trip-level data were collected and analyzed in R and ArcGIS. Results: Primary locations were confirmed to be 100% accurate when compared to known addresses. Based on the locations of the breadcrumbs, we were able to successfully identify frequently visited locations and general travel patterns. Based on the reported time from the breadcrumbs, we could assess number of trips driven in daylight vs. night. Data on additional events while driving allowed us to compute the number of adverse driving alerts over the course of the 5-month period. Conclusions: This pilot study indicated that Driving Profiles for older adults can be created and compared month-to-month or year-to-year, allowing researchers to identify changes in driving patterns that are unavailable in controlled conditions.

Studying critical pedestrian behavioral changes for the safety assessment at signalized crosswalks

Pedestrian-vehicle conflicts are one of the most important safety concerns at signalized intersections especially in urban areas. Conflicting vehicles and pedestrians select their maneuvers by predicting the other user behavior. Sudden behavioral changes of pedestrians such as sudden speed change (acceleration or deceleration) cannot be predicted by drivers, which can lead to safety hazards especially if these sudden behavioral changes occur near conflict areas. In this study, continuous pedestrian speed profiles were analyzed at signalized crosswalks to investigate the existence of such behavioral changes. A methodology is proposed to identify significant sudden changes of pedestrian speeds. The locations and timings of these sudden speed change events were analyzed, and the influencing factors such as crosswalk geometry and signal timing were studies and evaluated. Five signalized crosswalks at three intersections in Nagoya City were videotaped for analysis. Individual pedestrian maneuvers were extracted with image processing software. Empirical analysis showed that sudden acceleration events were observed at the entrance points to the pedestrian-vehicle conflict area, which highlights the significance of these events to pedestrian-vehicle conflict analysis. A multinomial logit model was developed to estimate the probability of a pedestrian making a sudden speed change as a function of different influencing factors. The results implied that the entering speed, necessary speed to finish crossing before the onset of the pedestrian signal red phase, and crosswalk length have a significant impact on speed change choices. This paper presents important suggestions to understanding pedestrian maneuvers in detail from the viewpoint of safety.

A Portable Emissions Measurement System (PEMS) study of NOx and primary NO2 emissions from Euro 6 diesel passenger cars and comparison with COPERT emission factors

Real world emissions of oxides of nitrogen (NOx) often greatly exceed those achieved in the laboratory based type approval process. In this paper the real world emissions from a substantial sample of the latest Euro 6 diesel passenger cars are presented with a focus on NOx and primary NO2. Portable Emissions Measurement System (PEMS) data is analysed from 39 Euro 6 diesel passenger cars over a test route comprised of urban and motorway sections. The sample includes vehicles installed with exhaust gas recirculation (EGR), lean NOx traps (LNT), or selective catalytic reduction (SCR). The results show wide variability in NOx emissions from 1 to 22 times the type approval limit. The average NOx emission, 0.36 (sd. 0.36) g km−1, is 4.5 times the Euro 6 limit. The average fraction primary NO2 (fNO2) is 44 (sd. 20) %. Higher emissions during the urban section of the route are attributed to an increased number of acceleration events. Comparisons between PEMS measurements and COPERT speed dependent emissions factors show PEMS measurements to be on average 1.6 times higher than COPERT estimates for NOx and 2.5 times for NO2. However, by removing the 5 most polluting vehicles average emissions were reduced considerably.

Investigating Driver Sympathetic Arousal under Short-term Loads and Acute Stress Events

This study involved an investigation of patterns of arousal in a driver’s sympathetic nervous system toward a system that can detect high cognitive workload, high emotional load, and acute stress (surprise or panic) experiences in drivers. Humans are exposed to cognitive and physical stressors in the driving environment that can be exacerbated when drivers are operating under the cognitive effects of incidental emotions or secondary task loads. Each type of stressor can negatively affect the control of complex operational systems, such as a vehicle, in different ways. The body’s sympathetic autonomous nervous system (the “fight or flight” system) triggers several physiological changes in the body, such as perspiratory and cardiac dynamics, in order to prepare the human to defend themselves or run away. Physiological sensor systems can therefore be used to collect data on these physiological changes (such as heart rate variability (HRV; Taelman, Vandeput, Spaopon, & Van Huffel, 2009) and skin conductance response (SCR; Boucsein, 2012; Shi, Ruiz, Taib, Choi, & Chen, 2007; Villarejo, Zapirain, & Zorrilla, 2012). Data processing techniques can be applied to identify patterns in physiological response across multiple variables and time windows that are characteristics of potentially problematic driver mental states. As a first step toward developing an online system for detecting potentially-problematic driver mental states, this study sought to identify patterns in HRV and SCR data associated with each of these states, and to investigate the predictive power of such an algorithm for explaining aspects of driving behavior. Eighty-eight people (with equal representation from each sex and each of two age groups) participated in a driving simulator study. The simulation scenarios consisted of a simulated rural highway with multiple predetermined segments where secondary task loads were applied. After a physiological baselining procedure and adequate practice with the driving and secondary tasks, participants completed scenarios under each of the six driving conditions: a “Normal” drive with a simple roadway and no secondary tasks, four “Loaded” drives that included driving-related loads (e.g., construction zones) and some additional secondary tasks designed to impose analytical cognitive, emotional, and motoric (e.g., texting task) loads. A final scenario included varied combinations of these loads and a unique surprising “Failure” event (triggered acceleration in the vehicle that mimicked unintended acceleration problems). HRV and SCR were measured throughout the experiment using Zephyr Bioharness3 and Shimmer3 sensor systems, respectively, and numerous third-party software packages were used to process the data and identify noteworthy patterns. This presentation will report the analytical results of three dependent variables: HRV, SCR-amplitude (i.e., the magnitude of characteristic increases in arousal during sympathetic response), and SCR-frequency (i.e., the frequency of skin conductance responses identified within a predetermined time window). HRV (measured over time windows of a few seconds, as well as of several minutes) and SCR-Frequency were significantly sensitive to changes in loading, and some patterns in dynamics among multiple measures can be used to differentiate the designed mental states, although further testing is underway to refine and validate these findings. In particular, SCR- amplitude may be an effective way to distinguish acute stress events, as this measure shows a significant and substantial change within 2.5 seconds after realization of the unintended acceleration event. In addition to discussing these results, the current and future efforts in the development of an online driver “stressor detector” and mitigation system will be introduced in the presentation as well.

Total float management: computerized technique for construction delay analysis

Developing a holistic and accurate delay analysis software is still challenging the current delay analysis practices. Most of the existing delay analysis techniques are not programmed and still depend on manual calculations. The currently available computerized delay analysis techniques are still limited, suffer from many drawbacks, and do not consider many of the delay analysis situations. This paper introduces web-based software called total float management (TFM) software for analyzing delay claim utilizing TFM delay analysis technique. The TFM technique depends on day-by-day analysis, which gives more accurate analysis over other techniques. The software has the ability to import schedule data from Primavera P6 and Microsoft Project (MS project) software in various formats. This feature makes analysis easier and reduces the time required for data input. Many other features are included in the TFM software, such as the ability to address concurrent delays, change orders, and acceleration events.

Particle diffusion and localized acceleration in inhomogeneous AGN jets – II. Stochastic variation

We study the stochastic variation of blazar emission under a 2-D spatially resolved leptonic jet model we previously developed. Random events of particle acceleration and injection in small zones within the emission region are assumed to be responsible for flux variations. In addition to producing spectral energy distributions that describe the observed flux of Mrk 421, we further analyze the timing properties of the simulated light curves, such as the power spectral density (PSD) at different bands, flux-flux correlations, as well as the cross-correlation function between X-rays and TeV {\gamma}-rays. We find spectral breaks in the PSD at a timescale comparable to the dominant characteristic time scale in the system, which is usually the pre-defined decay time scale of an acceleration event. Cooling imposes a delay, and so PSDs taken at lower energy bands in each emission component (synchrotron or inverse Compton) generally break at longer timescales. The flux-flux correlation between X-rays and TeV {\gamma}-rays can be either quadratic or linear, depending on whether or not there are large variation of the injection into the particle acceleration process. When the relationship is quadratic, the TeV flares lag the X-ray flares, and the optical & GeV flares are large enough to be comparable to the ones in X-ray. When the relationship is linear, the lags are insignificant, and the optical & GeV flares are small.

Innovative Insurance Schemes: Pay as/how You Drive

The objective of this paper is to provide a critical review of the most popular and often implemented methodologies related to Usage-based motor insurance (UBI). UBI schemes, like Pay-as-you-drive (PAUD) and Pay-how-you-drive (PHUD), are a new innovative concept that has recently started to be commercialized around the world. The main idea is that instead of a fixed price, drivers have to pay a premium based on their driving behaviour and degree of exposure. Despite the fact that it has been implemented only for a few years, it is proven to be a very promising practice with a significant potential impact on traffic safety. This is achieved by the financial incentive given to drivers in order to improve their driving behaviour such as reducing the number of harsh braking and acceleration events taking place or reducing their degree of exposure such as their annual mileage, the time of the day travelling etc. and therefore reduces traffic risk. It can also be beneficial towards other social objectives such as traffic congestion and pollution emissions reduction.To this end, the existing literature on UBI schemes is critically reviewed and research gaps are identified. Findings show that there is a multiplicity and diversity of several research studies accumulated in modern literature examining the correlation between PAUD (based on driver's exposure) and PHUD (based on driving behaviour) schemes and traffic risk in order to determine accident risk. Moreover, it seems that UBI implementation would eliminate the cross-subsidies phenomenon, which implies less insurance costs for goods and less exposed drivers. Moreover, it would also provide a strong motivation for drivers to improve their driving behaviour and reduce their degree of exposure by receiving feedback and monitoring their driving performance and exposure which would result in traffic risk reduction both totally and individually.

A study on crossing speed profiles of pedestrians at signalized crosswalks

Pedestrian–vehicle conflicts are one of the most important safety concerns especially at intersections. Of total traffic fatalities, 30% and 36% are pedestrians in Qatar and in Japan, respectively (National Police Agency in Japan, 2015). Although pedestrians at signalized intersections are given priority during the green phase, turning vehicles in conflict often do not give the right of way to pedestrians but tend to compete for it. Furthermore, long crosswalks, short green times, and other reasons may cause pedestrians to rush or suddenly change their speed without paying attention to the surrounding conditions (Iryo-Asano et al. 2014). The sudden changes in pedestrian behavior while crossing cannot be predicted by the driver, which can cause severe conflicts. Therefore, the possible behavioral changes of pedestrians should be studied so that surrogate safety measures such as post-encroachment time can be quantitatively estimated to provide a reliable assessment of pedestrian–vehicle conflicts and their severities. Continuous pedestrian speed profiles were analyzed at signalized crosswalks considering the impact of crosswalk geometry and signal timing. Five signalized crosswalks at three intersections in Nagoya City were videotaped and individual pedestrian maneuvers were extracted by image processing. A stepwise speed function is proposed to identify significant sudden changes in individual pedestrian speed profiles. The locations and timings of these sudden speed change events were analyzed, and the influencing factors were statistically evaluated. Empirical analysis showed that sudden acceleration events were observed at the entrance points to the pedestrian–vehicle conflict area, which highlights the significance of these events to pedestrian–vehicle conflict analysis. More than a quarter of all acceleration events occurred just after the onset of the pedestrian flashing green signal indication. Furthermore, it is concluded that long crosswalks have higher percentage of speed change occurrence and as a result higher risk of crashes. In this regard, the application of two-stage pedestrian crossing is a potential solution to reduce crosswalk length and the possibility of having unpredicted pedestrian behavioral changes. In general, the results implied that pedestrian entering speed to crosswalk, necessary speed to finish crossing before the onset of the pedestrian red signal indication, and crosswalk length have a significant impact on pedestrian speed change choices.

Glacier velocity variability due to rain-induced sliding and cavity formation

The largest accelerations of glaciers and ice sheets are caused by changes in basal slip. Here we examine glacier speed and rain-induced accelerations using a near-continuous 26-month-long GNSS time series from a large maritime glacier (Tasman Glacier, New Zealand). During periods of high rain-rate we observe short-term increases in 24-hour speeds to up to 15-times background speed. Speeds calculated over 3-hour intervals increase to up to 36-times background speed. Acceleration events correspond with times when bed separation also increases rapidly indicating that the acceleration is associated with the growth of water-filled cavities at the bed. Glacier speeds then decrease prior to the reduction in bed separation, indicating cavity growth, not cavity extent, controls the acceleration. The short-term accelerations are superimposed on longer-term periods of enhanced velocity that persist for days to weeks and decay at similar rates to bed separation estimates and proglacial lake levels. A power-law relationship between observed rain-rate and speed exists at the glacier front and exhibits no apparent upper bound. Overall, we estimate that rain-induced accelerations account for 11–14% of Tasman Glacier's displacement during the observation period. The rain-rate–velocity relationship and the rainfall record since 2001 indicate that rain-induced speed-up events result in interannual variability in glacier displacement of 2%–13%.

Performance and Emissions of a Heavy-Duty Truck during the UDDS Driving Cycle: Simulation Analysis

AbstractThis study examines engine and vehicle performance during the UDDS (urban dynamometer driving schedule) driving cycle of a heavy-duty truck. The most important and novel feature of the analysis is the application of a zero-dimensional model for the simulation of the thermodynamic processes on a crank angle degree basis; a considerable differentiation from the usual mean-value modeling approach of past research is thus accomplished, with the ability to provide insight into the relevant engine processes. The simulation covers the behavior of the whole vehicle (tires, suspension, gearbox, driver, etc.) during the cycle, focusing on the prominent engine emissions (soot, NOx, and CO2) at each acceleration event. Road-type, tire-type, and vehicle-size effects are also taken into account through a relevant parametric study.

Solar wind conditions leading to efficient radiation belt electron acceleration: A superposed epoch analysis

AbstractDetermining preferential solar wind conditions leading to efficient radiation belt electron acceleration is crucial for predicting radiation belt electron dynamics. Using Van Allen Probes electron observations (>1 MeV) from 2012 to 2015, we identify a number of efficient and inefficient acceleration events separately to perform a superposed epoch analysis of the corresponding solar wind parameters and geomagnetic indices. By directly comparing efficient and inefficient acceleration events, we clearly show that prolonged southward Bz, high solar wind speed, and low dynamic pressure are critical for electron acceleration to >1 MeV energies in the heart of the outer radiation belt. We also evaluate chorus wave evolution using the superposed epoch analysis for the identified efficient and inefficient acceleration events and find that chorus wave intensity is much stronger and lasts longer during efficient electron acceleration events, supporting the scenario that chorus waves play a key role in MeV electron acceleration.

Integrated seismic source model of the 2015 Gorkha, Nepal, earthquake

AbstractWe compared spatiotemporal slip‐rate and high‐frequency (around 1 Hz) radiation distributions from teleseismic P wave data to infer the seismic rupture process of the 2015 Gorkha, Nepal, earthquake. For these estimates, we applied a novel waveform inversion formulation that mitigates the effect of Green's functions uncertainty and a hybrid backprojection method that mitigates contamination by depth phases. Our model showed that the dynamic rupture front propagated eastward from the hypocenter at 3.0 km/s and triggered a large‐slip event centered about 50 km to the east. It also showed that the large‐slip event included a rapid rupture acceleration event and an irregular deceleration of rupture propagation before the rupture termination. Heterogeneity of the stress drop or fracture energy in the eastern part of the rupture area, where aftershock activity was high, inhibited rupture growth. High‐frequency radiation sources tended to be in the deeper part of the large‐slip area, which suggests that heterogeneity of the stress drop or fracture energy there may have contributed to the damage in and around Kathmandu.

Ground-penetrating radar observations for estimating the vertical displacement of rotational landslides

Abstract. The objective of this paper is to demonstrate the applicability of ground-penetrating radar (GPR) for monitoring the displacement of slow-moving landslides. GPR data are used to estimate the vertical movement of rotational slides in combination with other surveying techniques. The study area is located along the Normandy coast (northeast France) where several rotational landslides are continuously affected by a seasonal kinematic regime (low displacement rates of 0.01 to 0.10 m yr−1) and periodically by major acceleration events (high displacement rates of 1.0 to 7.0 m per event).

A passive microsystem for detecting multiple acceleration events beyond a threshold

A fully mechanical microsystem for detecting multiple acceleration threshold violations is presented. It combines a seismic mass as a part of a ratcheting mechanism so that discrete positions are enabled depending on the external acceleration forces.A numerical model describing the dynamic system behavior has been developed. The fabricated system demonstrator is investigated utilizing impact tests, and the numerical model is verified by comparing the model with the measurement values. Various acceleration thresholds between 5g and 30g could safely be measured. Additionally, the counter can be re-initialized utilizing an electrostatic actuator for releasing the ratcheting mechanism.This recording of acceleration events does not require electrical energy for detection nor for storage; hence it is suitable for monitoring of sparse but critical acceleration or impact events over large time periods. The system design is prepared for an electrical read-out by, e.g. RFID transponders or comparable systems that transmit the position of the seismic mass within the ratcheting mechanism.

Effects of gravity on the acceleration and pair statistics of inertial particles in homogeneous isotropic turbulence

Within the context of heavy particles suspended in a turbulent airflow, we study the effects of gravity on acceleration statistics and radial relative velocity (RRV) of inertial particles. The turbulent flow is simulated by direct numerical simulation (DNS) on a 2563 grid and the dynamics of O(106) inertial particles by the point-particle approach. For particles/droplets with radius from 10 to 60 μm, we found that the gravity plays an important role in particle acceleration statistics: (a) a peak value of particle acceleration variance appears in both the horizontal and vertical directions at a particle Stokes number of about 1.2, at which the particle horizontal acceleration clearly exceeds the fluid-element acceleration; (b) gravity constantly disrupts quasi-equilibrium of a droplet’s response to local turbulent motion and amplifies extreme acceleration events both in the vertical and horizontal directions and thus effectively reduces the inertial filtering mechanism. By decomposing the RRV of the particles into three parts: (1) differential sedimentation, (2) local flow shear, and (3) particle differential acceleration, we evaluate and compare their separate contributions. For monodisperse particles, we show that the presence of gravity does not have a significant effect on the shear term. On the other hand, gravity suppresses the probability distribution function (pdf) tails of the differential acceleration term due to a lower particle-eddy interaction time in presence of gravity. For bidisperse cases, we find that gravity can decrease the shear term slightly by dispersing particles into vortices where fluid shear is relatively low. The differential acceleration term is found to be positively correlated with the gravity term, and this correlation is stronger when the difference in colliding particle radii becomes smaller. Finally, a theory is developed to explain the effects of gravity and turbulence on the horizontal and vertical acceleration variances of inertial particles at small Stokes numbers, showing analytically that gravity affects particle acceleration variance both in horizontal and vertical directions, resulting in an increase in particle acceleration variance in both directions. Furthermore, the effect of gravity on the horizontal acceleration variance is predicted to be stronger than that in the vertical direction, in agreement with our DNS results.

Construct validity and educational role for motion analysis in a laparoscopic trainer.

Laparoscopic models for ex vivo up-skilling are becoming increasingly important components of surgical education. This study aims to establish the construct validity and possible educational role of a new laparoscopic box trainer equipped with a motion-tracking device. A structured questionnaire was used to assign participants into novice, intermediate, or expert categories according to level of experience in minimal access surgery (MAS). Participants carried out a well-defined intracorporeal suturing task. Three specific motion analysis parameters (MAPs)-velocity, acceleration, and range-were measured and analyzed as movements in the four degrees of freedom available in traditional MAS using tracking sensors at the trocar insertion sites. The number of extreme velocity and acceleration events in all four degrees of freedom proved capable of differentiating between participants in the three categories of surgical experience using an ANOVA test (p<0.001). Post hoc analysis confirmed these differences in the number of extreme velocity and acceleration events between all groups tested except for the velocity of the roll between the intermediates and experts. These findings confirm construct validity for this new laparoscopic box trainer system, which employs a novel analysis based on motion parameters. Motion parameters provide information regarding the overall smoothness of the operator's instrument handling, an important aspect of a surgeon's technique. This preliminary data will be used to design a simulator with real-time motion feedback to enhance its educational value.

Effect of Driving Behavior and Vehicle Characteristics on Energy Consumption of Road Vehicles Running on Alternative Energy Sources

Road vehicles using gasoline, a gasoline-electric hybrid, diesel, methane, hydrogen, and a hydrogen-electric hybrid were investigated for differences in energy consumption as a function of driving behavior and vehicle characteristics. The results show that driving behavior has a large impact on energy consumption of vehicles in real traffic. Forceful acceleration events were linked with increased energy consumption, while moderate acceleration and steady average speed were linked with energy consumption benefits. In vehicles with regenerative braking, the frequency of forceful braking events is linked with a statistically significant lesser energy consumption as energy is generated for the vehicle during those events. The tested hydrogen- and methane-powered vehicles were found to have the overall best results regarding energy consumption.

MAGNETIC RECONNECTION TURBULENCE IN STRONG GUIDE FIELDS: BASIC PROPERTIES AND APPLICATION TO CORONAL HEATING

A current sheet susceptible to the tearing instability is used to drive reconnection turbulence in the presence of a strong guide field. Through nonlinear gyrokinetic simulations, the dependencies of central quantities such as the heating rate on parameters like collisionality or plasma β are studied, revealing that linear physics tends to predict only some aspects of the quasi-saturated state, with the nonlinear cascade responsible for additional features. For the solar corona, it is demonstrated that the kinetic heating associated with this type of turbulence agrees quantitatively with observational volumetric heating rates. In the context of short particle acceleration events, the self-consistent emergence of plasmoids or flux ropes in the turbulent bath is found to be important: ubiquitously occurring merger events of these objects cause strong bursts in the heating rate, the timescale of which is consistent with nanoflare observations. Furthermore, anisotropy of the temperature fluctuations is seen to emerge, hinting at a new means of generating coronal ion temperature anisotropy in the absence of cyclotron resonances.

Coming Clean

The Clean Snowmobile Challenge (CSC) is a Society of Automotive Engineers (SAE) student design competition. It was first held in 2000 in Jackson Hole, Wyoming, near Yellowstone National Park. The purpose of the competition is for students to experience design by modifying an existing snowmobile to reduce the environmental impact in environmentally sensitive areas and on public trails while maintaining performance. The main methods for reducing environmental impact are to reduce noise and exhaust emissions from the snowmobiles and improve fuel economy. Students compete in several events that measure the performance of their snowmobiles, including a 100-mi (161-km) endurance and fuel economy run, SAE standardized sound testing, emissions measurement, and acceleration and handling events. Additional events are used to evaluate the "project management" skills of the team. These include an oral presentation, a technical paper, and determining the cost of the modified snowmobile.

Effect of Nitrocellulose Gasifying Binder on Thrust Performance and High‐g Launch Tolerance of Miniaturized Nanothermite Thrusters

AbstractNanothermites are promising propellants for miniaturized thruster applications, but in their pure state can be very sensitive to ignition stimuli and prone to phase separation. Consequentially, a need exists for desensitizing binders that do not inhibit nanothermite thrust performance. We investigate the effects of incorporating small weight concentrations of nitrocellulose as a gasifying binder in bismuth trioxide‐aluminum nanothermites. Thrust measurements revealed improvements in specific impulse up to 63.2 s using nitrocellulose. The launch tolerance of the nanothermites in response to high‐g acceleration was also explored and substantial improvements were realized for nanothermites prepared with nitrocellulose. As small as 5 % nitrocellulose content suppressed the sensitivity of the nanothermites to less than 1 % ignition probability after exposure to 30 kg acceleration events. Some nanothermite charges experimentally survived up to 90 kg loads. Most importantly, nitrocellulose predictably modulated the thrust performance and ignition sensitivity of the nanothermites as a function of weight content. Employing nitrocellulose as a binder, high performance nanothermite propellants can be synthesized for miniaturized thruster applications with tailored impulse generation and ignition sensitivity.