Threshold Of Human Perception Research Articles

The Intelligent Driver Model with stochasticity – New insights into traffic flow oscillations

Traffic flow oscillations, including traffic waves, are a common yet incompletely understood feature of congested traffic. Possible mechanisms include traffic flow instabilities, indifference regions or finite human perception thresholds (action points), and external acceleration noise. However, the relative importance of these factors in a given situation remains unclear. We bring light into this question by adding external noise and action points to the Intelligent Driver Model and other car-following models thereby obtaining a minimal model containing all three oscillation mechanisms. We show analytically that even in the subcritical regime of linearly stable flow (order parameter ϵ < 0), external white noise leads to spatiotemporal speed correlations “anticipating” the waves of the linearly unstable regime. Sufficiently far away from the threshold, the amplitude scales with (−ϵ)−0.5. By means of simulations and comparisons with experimental car platoons and bicycle traffic, we show that external noise and indifference regions with action points have essentially equivalent effects. Furthermore, flow instabilities dominate the oscillations on freeways while external noise or action points prevail at low desired speeds such as vehicular city or bicycle traffic. For bicycle traffic, noise can lead to fully developed waves even for single-file traffic in the subcritical regime.

Analysis of laser speckle reduction utilizing microlens-array-based projection screen.

This paper focuses on the theoretical analyzation of laser speckle reduction by utilizing a microlens array (MLA). A theoretical model was established to describe the screen effect on speckle reduction, taking into account MLA cell size and on-screen projection/detection resolution area size. The relationship between the speckle contrast ratio (SCR) of a projection system and the cell size of an MLA was studied and investigated. A guideline for choosing an MLA that is able to suppress SCR below the threshold of human perception is proposed from the obtained results.

The Intelligent Driver Model with Stochasticity -New Insights Into Traffic Flow Oscillations

Traffic flow oscillations, including traffic waves, are a common yet incompletely understood feature of congested traffic. Possible mechanisms include traffic flow instabilities, indifference regions or finite human perception thresholds (action points), and external acceleration noise. However, the relative importance of these factors in a given situation remains unclear. We bring light into this question by adding external noise and action points to the Intelligent Driver Model and other car-following models thereby obtaining a minimal model containing all three oscillation mechanisms. We show analytically that even in the subcritical regime of linearly stable flow (order parameter ϵ < 0), external white noise leads to spatiotemporal speed correlations “anticipating” the waves of the linearly unstable regime. Sufficiently far away from the threshold, the amplitude scales with (−ϵ)−0.5. By means of simulations and comparisons with experimental car platoons and bicycle traffic, we show that external noise and indifference regions with action points have essentially equivalent effects. Furthermore, flow instabilities dominate the oscillations on freeways while external noise or action points prevail at low desired speeds such as vehicular city or bicycle traffic. For bicycle traffic, noise can lead to fully developed waves even for single-file traffic in the subcritical regime.

Tilt thresholds for acceleration rendering in driving simulation

The tilt coordination technique is used in driving simulation for reproducing a sustained linear horizontal acceleration by tilting the simulator cabin. If combined with the translation motion of the simulator, this technique increases the acceleration rendering capabilities of the whole system. To perform this technique correctly, the rotational motion must be slow to remain under the perception threshold and thus be unnoticed by the driver. However, the acceleration to render changes quickly. Between the slow rotational motion limited by the tilt threshold and the fast change of acceleration to render, the design of the coupling between motions of rotation and translation plays a critical role in the realism of a driving simulator. This study focuses on the acceptance by drivers of different configurations for tilt restitution in terms of maximum tilt angle, tilt rate, and tilt acceleration. Two experiments were conducted, focusing respectively on roll tilt for a 0.2 Hz slaloming task and on pitch tilt for an acceleration/deceleration task. The results show what thresholds have to be followed in terms of amplitude, rate, and acceleration. These results are far superior to the standard human perception thresholds found in the literature.

INCE/J Vibration Measurement Manual for Buildings—Part 2: On the assessment based on the vibration

This paper discusses the assessment of building vibration in terms of human responses based on vibration measurements specified by the Vibration Measurement Manual for Buildings developed by the Technical Subcommittee on Environmental Vibration Evaluation of the Institute of Noise Control Engineering of Japan. As stated in some of the current international and national standards, building vibration could cause adverse comments from occupants when the vibration magnitude is in excess of human perception only slightly. For the assessment of building vibration based on the measurement manual, therefore, a range of human vibration perception threshold was derived from the previous studies that determined the perception thresholds in experiment involving human subjects. The vibration perception threshold range implies a range of vibration magnitude for different frequencies that may correspond to lowest vibration magnitudes people with different sensitivities to vibration can detect. The vibration magnitude within or in excess of the perception range may be assessed as a magnitude that can be perceived by occupant at different possibilities. The assessment with the vibration perception threshold range does not necessarily show if the building vibration to be assessed has a magnitude high enough to cause adverse comment.

Incorporating Human Perception With the Motion Washout Filter Using Fuzzy Logic Control

Nowadays, classical washout filters are extensively used in commercial motion simulators. Even though there are several advantages for classical washout filters, such as short processing time, simplicity and ease of adjustment, they have several shortcomings. The main disadvantage is the fixed scheme and parameters of the classical washout filter cause inflexibility of the structure and thus the resulting simulator fails to suit all circumstances. Moreover, it is a conservative approach and the platform cannot be fully exploited. The aim of this research is to present a fuzzy logic approach and take the human perception error into account in the classical motion cueing algorithm, in order to improve both the physical limits of restitution and realistic human sensations. The fuzzy compensator signal is applied to adjust the filtered signals on the longitudinal and rotational channels online, as well as the tilt coordination to minimize the vestibular sensation error below the human perception threshold. The results indicate that the proposed fuzzy logic controllers significantly minimize the drawbacks of having fixed parameters and conservativeness in the classical washout filter. In addition, the performance of motion cueing algorithm and human perception for most occasions is improved.

A flexible multimodal tactile display for delivering shape and material information

The growing complexity of telemanipulation tasks calls for increased realism and intuitiveness of the interaction between the user and the master control. Humans perceive multiple haptic features of an object such as its stiffness, temperature, and shape, and rely on this multimodal information to achieve dexterous manipulation. However, to date, remote manipulators rarely provide haptic information to the operator. Moreover, current multimodal displays are often too rigid and bulky to be integrated into the manipulator. Thus, to improve the quality of teleoperation, there is a high demand for flexible devices that are capable of matching the skin's curvature while delivering multimodal haptic information to the operator. In this paper, we present a flexible tactile display delivering tactile and thermal stimuli to the user’s skin. We propose a hybrid electromagnetic-pneumatic actuation to operate a 2×2 array of tactile cells. Each cell provides a repetitive stimulation with a force and an indentation that are above the human perception threshold for the finger, palm, and forearm. In addition, the temperature of the display’s surface is controlled using a Peltier element attached to an air-cooled heatsink. By providing a reproducible cooling gradient, our display simulates common materials encountered in the daily environment. User study results show that (1) the tactile stimulation is perceived well and (2) the identification rates of objects simulated with the display were comparable to those obtained with real objects. Unlike previous devices, the thermal stimulation is delivered while the display is in constant contact with the user’s skin, a necessary requirement for teleoperation. These results demonstrate the potential of our device as a promising tactile display for providing haptic feedback in teleoperation.

Performance-Based Design of High-Rise Buildings for Occupant Comfort

AbstractThis paper introduces a framework for the performance-based design (PBD) of high-rise buildings with respect to the occupant comfort performance objective. The performance is expressed in terms of the probability—conditional on the wind event intensity—that the fraction of the building occupants on one floor that perceive the motion is greater than a chosen threshold value. The framework is fully probabilistic, and numerous uncertainties affecting both the structural response and the human perception threshold are considered in the assessment of the exceedance probability. In addition, a new database-enabled online analysis module based on the proposed PBD framework [Performance-Based Data-Enabled Design module for Occupant Comfort (PBDED-OC)] is presented. The PBDED-OC allows the assessment of the occupant comfort performance of a tall building by taking advantage of databases of high-frequency base balance measurements or by adopting specific user-supplied wind tunnel data and is envisaged to be...

Polarization and visibility of higher-order rainbows

The degree of polarization of rainbows of order k with k≥3 is bounded in the interval [75%, 78%], where 75% is the limit for k→∞. A polarization filter can improve the signal-to-background ratio of the third and fourth rainbows by a factor of 2, which may lift their visibilities in natural circumstances above the threshold of human visual perception. Under optimal circumstances, the latter may be true for the recently photographed green fingerprint of the fifth rainbow, even without the aid of a polarization filter. The prospects for observing the sixth rainbow are unclear. There exists a possibility that the signal of the natural seventh rainbow (appearing at 64° from the Sun) may be separated from its background if photographed under perfect conditions through a polarization filter.

Human speckle perception threshold for still images from a laser projection system.

We study the perception of speckle by human observers in a laser projector based on a 40 persons survey. The speckle contrast is first objectively measured making use of a well-defined speckle measurement method. We statistically analyse the results of the user quality scores, revealing that the speckle perception is not only influenced by the speckle contrast settings of the projector, but it is also strongly influenced by the type of image shown. Based on the survey, we derive a speckle contrast threshold for which speckle can be seen, and separately we investigate a speckle disturbance limit that is tolerated by the majority of test persons.

A Modified Model of the Just Noticeable Depth Difference and Its Application to Depth Sensation Enhancement

The just noticeable depth difference (JNDD) describes the threshold of human perception of the difference in the depth. In flat-panel-based three-dimensional (3-D) displays, the JNDD is typically measured by changing the depth difference between displayed image objects until the difference is perceivable. However, not only the depth, but also the perceived size changes when the depth difference increases. In this paper, we present a modified JNDD measurement method that adjusts the physical size of the object such that the perceived size of the object is maintained. We then apply the proposed JNDD measurement method to depth sensation enhancement. When the depth value difference between the objects is increased to enable the viewer to perceive the depth difference, the size of the objects is adjusted to maintain the perceived size of the objects. In addition, since the size change of the objects can produce a whole region, a depth-adaptive hole-inpainting technique is proposed to compensate for the hole region with high accuracy. The experimental results demonstrate the effectiveness of the proposed method.

Impact of mixed S. cerevisiae strains on the production of volatiles and estimated sensory profiles of Chardonnay wines

The global wine industry is mostly reliant on the use of active dry yeasts to conduct wine fermentations. The use of single industrial yeasts, however, may result in the loss of complexity or uniqueness of the wine bouquet; the option of fermenting grape musts with multiple active dried yeast strains could enhance the complexity and quality of wines. Two novel Burgundian Saccharomyces cerevisiae strains (C2, C6) were compared with six industrial yeast strains for fermentation of Chardonnay must. The volatile compounds in the wines were identified and quantified using gas chromatography–mass spectrometry. The concentrations of 18 volatile compounds (higher alcohols, ethyl esters, acetate esters, acetaldehyde, acetic acid) were compared using analysis of variance and radar diagrams. The concentration of volatile compounds in wines produced by industrial and Burgundian strains differed significantly. Principal component analyses of the volatile compounds (higher alcohols, ethyl esters, acetate esters) in the wines revealed that fermentations with individual and mixed Burgundian strains were more similar to one another than wines fermented with industrial strains. Calculation of odor active values (OAVs) allowed estimation of the sensory impact of each volatile compound. Radar diagrams of the OAVs revealed the estimated sensory profiles of the wine produced by industrial and Burgundian (individual, mixed) strains. The most distinguishing trait of the mixed novel Burgundian yeast strains was that they produced intermediate concentrations of most volatile compounds and that production of fruity aromas such as sweet fruit, strawberry, green apple, pear and banana were above the sensory threshold, while the production of nail polish, waxy, balsamic and vinegar were below the human perception threshold. The mixed culture of Burgundian yeast strains produced wines that were unique and more complex than wines produced with single industrial yeast strains.

Spatio-temporal variability of tastes and odors of drinking water within a distribution system

The threshold of human perception in the detection of tastes and odors (T&O) relating to compounds in drinking water is variable. For example, chlorine can be detected at the ppm level and geosmin can be perceived at the ppt level. In this paper, sensory tests (using a human panel), physicochemical analyses (total and free residual chlorine, temperature, metals, geosmin, and 2-methylisoborneol (2MIB)) and microbiological analyses (algae, Actinomycetes and heterotrophic plate count) were performed for water samples collected during a seventeen-month period at ten different locations of a municipal distribution network of Quebec City (Canada). The results showed that different flavors(1) assessed by a panel and aggregated into global flavor intensity (GFI) vary considerably spatially and seasonally. Multiple regression analysis showed that the factors best explaining the variability of GFI are (in order) the season, the location, the concentration of total residual chlorine and the presence of cyanobacteria. Results also demonstrate that chlorine has a masking effect on other T&O.

Modelling of non-linear elastic tissues for surgical simulation

Realistic modelling of the interaction between surgical instruments and human organs has been recognised as a key requirement in the development of high-fidelity surgical simulators. Primarily due to computational considerations, most of the past real-time surgical simulation research has assumed linear elastic behaviour for modelling tissues, even though human soft tissues generally possess non-linear properties. For a non-linear model, the well-known Poynting effect developed during shearing of the tissue results in normal forces not seen in a linear elastic model. Using constitutive equations of non-linear tissue models together with experiments, we show that the Poynting effect results in differences in force magnitude larger than the absolute human perception threshold for force discrimination in some tissues (e.g. myocardial tissues) but not in others (e.g. brain tissue simulants).

Factors affecting perception thresholds of vertical whole-body vibration in recumbent subjects: Gender and age of subjects, and vibration duration

Some factors that may affect human perception thresholds of the vertical whole-body vibrations were investigated in two laboratory experiments with recumbent subjects. In the first experiment, the effects of gender and age of subjects on perception were investigated with three groups of 12 subjects, i.e., young males, young females and old males. For continuous sinusoidal vibrations at 2, 4, 8, 16, 31.5 and 63 Hz, there were no significant differences in the perception thresholds between male and female subjects, while the thresholds of young subjects tended to be significantly lower than the thresholds of old subjects. In the second experiment, the effect of vibration duration was investigated by using sinusoidal vibrations, at the same frequencies as above, modulated by the Hanning windows with different lengths (i.e., 0.5, 1.0, 2.0 and 4.0 s) for 12 subjects. It was found that the peak acceleration at the threshold tended to decrease with increasing duration of vibration. The perception thresholds were also evaluated by the running root-mean-square (rms) acceleration and the fourth power acceleration method defined in the current standards. The differences in the threshold of the transient vibrations for different durations were less with the fourth power acceleration method. Additionally, the effect of the integration time on the threshold was investigated for the running rms acceleration and the fourth power acceleration. It was found that the integration time that yielded less differences in the threshold of vibrations for different durations depended on the frequency of vibration.

Perception-Based Data Reduction for Haptic Force-Feedback Signals Using Velocity-Adaptive Deadbands

In telepresence and teleaction (TPTA) systems, the transmission of haptic signals puts high demands on the applied signal processing and communication procedures. When running a TPTA session across a packet-based communication network (e.g., the Internet), minimizing the end-to-end delay results in packet rates of up to the applied sampling rate of the local control loops at the human system interface and the teleoperator. The perceptual deadband data reduction approach for haptic signals successfully addresses the challenge of high packet rates in networked TPTA systems and satisfies the strict delay constraints. In this paper, we extend the underlying perceptual model of the deadband approach by incorporating psychophysical findings on human force-feedback discrimination during operators' relative hand movements. By applying velocity-dependent perception thresholds to the deadband approach, we observe further improvement in efficiency and performance due to improved adaption to human haptic perception thresholds. The psychophysical experiments conducted reveal improved data reduction performance of our proposed haptic perceptual coding scheme without impairing the user experience. Our results show a high data reduction ability of up to 96% without affecting system transparency or the operator's task performance.

Filming the invisible – time-resolved visualization of compressible flows

Essentially all processes in gasdynamics are invisible to the naked eye as they occur in a transparent medium. The task to observe them is further complicated by the fact that most of these processes are also transient, often with characteristic times that are considerably below the threshold of human perception. Both difficulties can be overcome by combining visualization methods that reveal changes in the transparent medium, and high-speed photography techniques that “stop” the motion of the flow. The traditional approach is to reconstruct a transient process from a series of single images, each taken in a different experiment at a different instant. This approach, which is still widely used today, can only be expected to give reliable results when the process is reproducible. Truly time-resolved visualization, which yields a sequence of flow images in a single experiment, has been attempted for more than a century, but many of the developed camera systems were characterized by a high level of complexity and limited quality of the results. Recent advances in digital high-speed photography have changed this situation and have provided the tools to investigate, with relative ease and in sufficient detail, the true development of a transient flow with characteristic time scales down to one microsecond. This paper discusses the potential and the limitations one encounters when using density-sensitive visualization techniques in time-resolved mode. Several examples illustrate how this approach can reveal and explain a number of previously undetected phenomena in a variety of highly transient compressible flows. It is demonstrated that time-resolved visualization offers numerous advantages which normally outweigh its shortcomings, mainly the often-encountered loss in resolution. Apart from the capability to track the location and/or shape of flow features in space and time, adequate time-resolved visualization allows one to observe the development of deliberately introduced near-isentropic perturbation wavelets. This new diagnostic tool can be used to qualitatively and quantitatively determine otherwise inaccessible thermodynamic properties of a compressible flow.

A sub-millimetric, 0.25 mN resolution fully integrated fiber-optic force-sensing tool for retinal microsurgery

Retinal microsurgery requires extremely delicate manipulation of retinal tissue where tool-to-tissue interaction forces are usually below the threshold of human perception. Creating a force-sensing surgical instrument that measures the forces directly at the tool tip poses great challenges due to the interactions between the tool shaft and the sclerotomy opening. We present the design and analysis of a force measurement device that senses distal forces interior to the sclera using 1-cm long, 160 microm diameter Fiber Bragg Grating (FBG) strain sensors embedded in a 0.5 mm diameter tool shaft. Additionally, we provide an algorithm developed to cancel the influence of environmental temperature fluctuations. The force-sensing prototype measures forces with a resolution of 0.25 mN in 2 DOF while being insensitive to temperature. Sub-millinewton resolution force sensors integrated into microsurgical instruments are feasible and have potential applications in both robotic and freehand microsurgery.

Diel vertical migration of Arctic zooplankton during the polar night

High-latitude environments show extreme seasonal variation in physical and biological variables. The classic paradigm of Arctic marine ecosystems holds that most biological processes slow down or cease during the polar night. One key process that is generally assumed to cease during winter is diel vertical migration (DVM) of zooplankton. DVM constitutes the largest synchronized movement of biomass on the planet, and is of paramount importance for marine ecosystem function and carbon cycling. Here we present acoustic data that demonstrate a synchronized DVM behaviour of zooplankton that continues throughout the Arctic winter, in both open and ice-covered waters. We argue that even during the polar night, DVM is regulated by diel variations in solar and lunar illumination, which are at intensities far below the threshold of human perception. We also demonstrate that winter DVM is stronger in open waters compared with ice-covered waters. This suggests that the biologically mediated vertical flux of carbon will increase if there is a continued retreat of the Arctic winter sea ice cover.

Engineering the Saccharomyces cerevisiae isoprenoid pathway for de novo production of aromatic monoterpenes in wine

Grape musts contain a variety of terpenols that significantly affect wine aroma. The amounts of these metabolites depend on the grape variety, and many cultivars are non-aromatic. Yeasts like Saccharomyces cerevisiae cannot produce and excrete monoterpenes efficiently, mainly due to their lack of monoterpene synthases. By metabolic engineering we have modified the isoprenoid biosynthesis pathway in a wine yeast strain of S. cerevisiae expressing the Clarkia breweri S-linalool synthase gene. Under microvinification conditions, without compromising other desirable and useful fermentative traits, the recombinant yeast efficiently excreted linalool to levels exceeding the threshold of human perception. Bearing in mind the possibility of (co-)expressing other genes that encode enzymes leading to the production of various aroma compounds and the feasibility of controlling the levels of their expression, the potential of this achievement for future genetic manipulation of wine varietal aroma or for use in other alcoholic drinks seems very promising.