Hazard perception of motorcyclists and car drivers

The current study compares hazard perception (HP) performance of 50 male drivers with and without a motorcycle license in order to generalize results. A video-based HP test, measuring reaction times to traffic scenes, was administered to these two groups of drivers. Participants with a motorcycle license performed better than participants without a motorcycle license. ANOVA indicated that learning improved linearly for participants with a motorcycle license but not for participants without a motorcycle license. No evidence that HP was predicted by age was found. HP scores for drivers who reported previous involvement in an accident were lower than for those who reported not being involved in an accident. The results are discussed in the context of sensitivity and response bias models.     

Mechanical properties of human enamel as a function of age and location in the tooth

Aging and the related changes in mechanical behavior of hard tissues of the human body are becoming increasingly important. In this study the influence of aging on the mechanical behavior of human enamel was evaluated using 3rd molars from young (18 < or = age < or = 30 years) and old (55 < or = age) patients. The hardness and elastic modulus were quantified using nanoindentation as a function of distance from the Dentin-Enamel Junction (DEJ) and within three different regions of the crown (i.e. cervical, cuspal and inter-cuspal enamel). Results of the evaluation showed that the elastic modulus and hardness increased with distance from the DEJ in all three regions examined, regardless of patient age. The largest increases with distance from the DEJ occurred within the cervical region of the old enamel. Overall, the results showed that there were no age-dependent differences in properties of enamel near the DEJ. However, near the tooth's surface, both the hardness (p < 0.025) and elastic modulus (p < 0.0001) were significantly greater in the old enamel. At the surface of the tooth the average elastic modulus of "old" enamel was nearly 20% greater than that of enamel from the young patients.     

Measurement of critical temperature as a function of field

The critical temperature has been measured for various magnet conductors as a function of the perpendicular applied magnetic field. The isothermal environment was provided by a variable temperature cryostat which fits into the bore of a 10 telsa solenoid. The temperature gradient across the sample volume was measured to be less than 25 millikelvins. The superconducting to normal state transition was measured resistively, using sample current densities from 0.01 to 2 A cm^?2. The maximum applied magnetic field was 10 T and varied less than 0.5% in the sample volume. The critical transport current range of the samples measured from tens to thousands of amperes in the presence of a 10 T perpendicular magnetic field at 4.2 K.     

Hazard perception and driving experience among novice drivers

The crash risk of novice drivers decreases rapidly during the first few months of post-licensing driving, indicating that some important safety-relevant traffic skills are learnt during this period. The present study tested the hypothesis that the risk decrease is related to improved hazard perception skills. A video-based hazard perception/reaction test, measuring reaction times to 31 traffic scenes, was administered to three groups of drivers, having held a licence for 1, 5, and 9 months, respectively, and to a group of drivers who had held their licences for several years. Average reaction times tended to decrease with experience, but the decrease was not significant. There were some significant differences in the expected direction for individual test items, indicating a possible effect of experience. One half of the situations were presented together with a secondary task, in order to investigate effects of increased mental load on hazard perception. Male novice drivers had relatively longer reaction times with the secondary task, compared to both female novice drivers and male experienced drivers. It is concluded that hazard perception as tested here is probably only a minor factor in explaining the initial risk decrease among novice drivers.     

Optimal multichannel estimation of the location of a target with nonoverlapping noise

We propose a new algorithm for estimating the location of an object in multichannel images when the noise is spatially disjointed from (nonoverlapping with) the target. This algorithm is optimal for nonoverlapping noise and for multichannel images in the maximum-likelihood sense. We consider the case in which the statistical parameters of the input scene are unknown and are estimated by observation. We assess the results for simulated images with white and Gaussian background, for a large scale of variances of the background noise, and different values of the contrast in the scene. We compare the results of this algorithm with the results obtained with two other algorithms, the optimal algorithm for monochannel nonoverlapping noise and the optimal algorithm for multichannel additive noise, and we show that in both cases improvement can be obtained. We show the efficiency of the estimation for real input scenes when the background noise is correlated clutter noise. This algorithm has the same complexity as correlation, and the improvement is obtained with no more calculation cost than with classic methods.     

Mirror recording system with a large field of view

A light-gathering system consisting of four mirrors with a large field of view has been developed. Two mirrors can be combined into one unit (double mirror). The design parameters of the system have been calculated and the problem on protection of the image plane from the foreign light has been considered. The objective proposed can be used in infrared imaging as well as in photometric and optical devices operating in the infrared region of the spectrum. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 78, No. 6, pp. 178–183, November–December, 2005.     

Hazard perception in novice and experienced drivers: The effects of sleepiness

One driver skill that has been found to correlate with crash risk is hazard perception ability. The purpose of this study was to investigate how hazard perception latencies change between high and low sleepiness for a high risk group (novice drivers) and a lower risk group (experienced drivers). Thirty-two novice drivers (aged 17-24 years) and 30 experienced drivers (aged 28-36) completed a validated video-based hazard perception test, in which participants were asked to anticipate genuine traffic conflicts in footage filmed from the driver's perspective, with separate groups tested at either 10 a.m. (lower sleepiness) or at 3 a.m. (higher sleepiness). We found a significant interaction between sleepiness and experience, indicating that the hazard perception skills of the more experienced drivers were relatively unaffected by mild increases in sleepiness while the inexperienced drivers were significantly slowed. The findings suggest that the disproportionate sleepiness-related accident involvement of young, inexperienced drivers could be partly due to a slowing of their ability to anticipate traffic hazards.     

匹配滤波器中参考目标位置对相关峰位置的影响

针对利用光学相关器识别运动多目标的精确定位问题,提出了参考图像目标置中的匹配滤波器设计方法.该方法根据场景图像中目标位置、匹配滤波器中参考目标位置和相关峰位置之间的关系,采用将目标放置在参考图像中心以克服单一目标和运动多目标识别过程中相关峰的不确定偏移.实验结果表明,在范德卢格特型光电混合相关器中,采用该方法设计匹配滤波器可以使相关峰位置与目标位置一一对应,并且能够直观的实时显示出被识别目标在场景图像中的位置,提高了运动目标的定位准确性和跟踪稳定性.     

Distortion of superfluid3He-B energy gap as a function of magnetic field

Ultrasound measurements of the pair-breaking edge of superfluid³He-B have provided a quantitative knowledge of the energy gap distortion in a magnetic field. The gap distortions obtained at very low temperatures for the three sound frequencies 168.3, 137.6 and 107 MHz are plotted against magnetic field. Results are consistent with theoretical estimates.     

Increase in the compensated field of view with a double-conjugate adaptive-optics system

We analyze and quantify the capabilities and limitations of a double-conjugate adaptive-optics system. In the proposed system the contribution of two turbulent layers is treated separately, with Rayleigh guide stars for the bottom layer, sodium guide stars for the top layer, and two adaptive mirrors conjugate to the respective layers. The system substantially increases the compensated field of view. We give calculated results for the estimated number of guide stars needed, the wave-front sensor, and the adaptive-mirror resolution. Simulation results are also presented, and the residual error remaining after correction in our proposed system is compared with a conventional single-adaptive-mirror system.     

On-road experiment to assess drivers’ detection of roadside targets as a function of headlight system,target placement,and target reflectance

Adaptive headlights swivel with steering input to keep the beams on the roadway as drivers negotiate curves. To assess the effects of this feature on driver’s visual performance, a field experiment was conducted at night on a rural, unlit, and unlined two-lane road during which 20 adult participant drivers searched a set of 60 targets. High- (n = 30) and low- (n = 30) reflectance targets were evenly distributed on straight road sections and on the inside or outside of curves. Participants completed three target detection trials: once with adaptive high-intensity discharge (HID) headlights, once with fixed HID headlights, and once with fixed halogen headlights. Results indicated the adaptive HID headlights helped drivers detect targets that were most difficult to see (low reflectance) at the points in curves found by other researchers to be most crucial for successful navigation (inside apex). For targets placed on straight stretches of road or on the outside of curves, the adaptive feature provided no significant improvement in target detection. However, the pattern of results indicate that HID lamps whether fixed or adaptive improved target detection somewhat, suggesting that part of the real world crash reduction measured for this adaptive system (Highway Loss Data Institute (HLDI), 2012a) may be due to the differences in the light source (HID vs. halogen). Depending on the scenario, the estimated benefits to driver response time associated with the tested adaptive (swiveling HID) headlights ranged from 200 to 380 ms compared with the fixed headlight systems tested.     

Expanding the field of view by polarization multiplexing

We introduce and demonstrate a method for expanding the field of view of a typical imaging system by multiplexing images encoded onto different polarization states and recovering them from a limited number of measurements.     

Moving target location and imaging using dual-speed velocity SAR

Velocity synthetic aperture radar (VSAR) is an effective tool for slowly moving target detection, location and imaging. However, it may mislocate fast moving targets because of the azimuth location ambiguity. The VSAR is generalised from flying with single speed to flying with dual-speed to resolve the azimuth location ambiguity. This new system is named dual-speed velocity SAR (DS-VSAR). Using DS-VSAR, the locations of both slowly and fast moving targets can be estimated accurately, and in the meantime the clutter can be suppressed. Some numerical examples are given to prove the effectiveness of DS-VSAR     

Fractional derivative operators for modeling the dynamic polarization behavior as a function of frequency and electric field amplitude

Polarization phenomena in ferroelectric materials are frequency-dependent, and the present article describes the use of a fractional derivative for the understanding of these phenomena as well as modeling them as functions of frequency and electric field amplitude. The focus was first directed toward the definition and validation of the proposed model through comparisons between simulations and measurements for high electrical field excitation amplitudes on a large frequency bandwidth (major hysteresis loops, measured over 4 decades). Subsequently, the same comparisons were made under ultra-weak as well as weak electric fields. Large frequency bandwidths were tested in each case, and it was shown that the fractional term provided a very accurate modeling of the dynamic behavior of the ferroelectrics. The dielectric permittivity coefficient along the polarization direction ^epsiv33 is a major parameter in ferroelectrics, and the frequency dependence of ^epsiv33 is correctly reproduced by the model. The time-dependence of the polarization reversal/variation was accurately simulated by a fractional derivation (a 0.5 order derivative), however, the use of a first-order derivation term (i.e., viscous losses) was in poor agreement with experimental results. It was found that the model was valid for large excitation field amplitudes as well as for large frequency bandwidths.     

Characteristics of Hermès flax fibres as a function of their location in the stem and properties of the derived unidirectional composites

The tensile mechanical properties of flax fibres from the Hermès variety are estimated according to their diameter and their location in the stems. The large scattering of these properties is ascribed to the variation of the fibre size along its longitudinal axis, as revealed by SEM observations. The higher values of the mechanical properties for the fibres issued from the middle of the stems are associated with the chemical composition of their cell walls. The mechanical properties of unidirectional flax fibre/epoxy matrix composites are studied as a function of their fibre content. The properties of the composites are lower than those expected from single fibre characteristics.     

Design of a static Fourier-transform spectrometer with increased field of view

We present several novel designs of static Fourier-transform spectrometers based on Wollaston prisms. By numerical modeling we show the increased field of view that can be obtained when an achromatic half-wave plate is included between the prisms or when prisms fabricated from positive and negative birefringent materials are combined. In addition, we model how a single Wollaston prism with an inclined optic axis produces a fringe plane localized behind its exit face, thus enabling the design of a static Fourier-transform spectrometer based on a single Wollaston prism.