Actual Reaction Time Research Articles

Experimental and Numerical Study on the Residence Time Distribution in a Stirred Membrane Reactor

The residence time distribution (RTD) of a reactor is a key factor related to the actual reaction time of reactants, by which the mixing in a reactor can be judged indirectly. Though many efforts have been made to study RTD in stirred tank reactors (STs) or membrane modules, research on RTD in a stirred membrane reactor (SMR) is still lacking. For this purpose, we investigated the influence of operating conditions on mixing in the SMR through experiments, obtained non-ideal mixing region by mathematical model fitting, and analyzed the flow field combined with CFD simulation. The critical value of the ratio of the discharge of impeller to the flow rate is 13.13 designed to reach ideal mixing in the SMR and that of the ratio of the mean residence time to the mixing time is 10 correspondingly. In addition, the RTD is independent of membrane permeability resistance.

Povećanje performansi aktivne kontrole otporne na greške u svemirskoj letelici korišćenjem neuronskih mreža

Actuator fault poses a challenge to the attitude control of spacecraft. Fault-tolerant control (active or passive) is often used to overcome this challenge. Active methods have better performance than passive methods and can manage a broader range of faults. However, their implementation is more difficult. One reason for this difficulty is the critical reaction time. The system may become unrecoverable if the actual reaction time becomes larger than the critical reaction time. This paper proposes using a feedforward neural network to reduce the actual reaction time in the active fault-tolerant control of spacecraft. Besides this improvement, using a feedforward neural network can increase the success percentage. Success percentage is the ratio of successful simulations to the total number of simulations. Simulation results show that for 200 simulations with random faults and initial conditions, the actual reaction time decreases by 73%, and the success percentage increases by 25%. Based on these results, the proposed controller is a good candidate for practical applications.

MPC-based switched driving model for human vehicle co-piloting considering human factors

In vehicle longitudinal control, improved comfort and reduced operation workload for human drivers are achieved with the ACC (Adaptive Cruise Control), which still requires the driver to maintain full attention on monitoring, meanwhile, the risk of distraction and fatigue rises resulting from the long-term supervising task, which has a strong impact on the successful takeover. The key point to make full use of ACC advantages and make up human’s weakness on supervising task is the reasonable arrangement of control time of ACC and human driver. In this paper, an MPC (Model Predictive Control) based optimized switching strategy of longitudinal driving authority transition is proposed, which aims to provide proper advice for human drivers to handover and takeover control authority, through minimizing the overall index consisted of the operation workload, fuel consumption, takeover risk and tracking errors. In addition, a new driver longitudinal model considering actual reaction time delay and insensitive distance perception of human drivers is proposed as well, which combines with ACC to constitute a typical switched control system called the switched driving model as the predictive model for MPC. The stable condition of the new driver longitudinal model is derived by using describing function method and a sufficient condition to ensure steady switched system is given by using the Lyapunov method and LMI approach. The results of simulator experiments show that the new driver model describes the car-following behavior of real human driver better. What’s more, the simulation results demonstrate that the performance index of switched driving is smaller than the human driving and ACC driving only, and the optimization time is short enough to meet the requirement of engineering practice.

Reduced multisensory facilitation in adolescents and adults on the Autism Spectrum

Individuals with autism are reported to integrate information from visual and auditory channels in an idiosyncratic way. Multisensory integration (MSI) of simple, non-social stimuli (i.e., flashes and beeps) was evaluated in adolescents and adults with (n = 20) and without autism (n = 19) using a reaction time (RT) paradigm using audio, visual, and audiovisual stimuli. For each participant, the race model analysis compares the RTs on the audiovisual condition to a bound value computed from the unimodal RTs that reflects the effect of redundancy. If the actual audiovisual RTs are significantly faster than this bound, the race model is violated, indicating evidence of MSI. Our results show that the race model violation occurred only for the typically-developing (TD) group. While the TD group shows evidence of MSI, the autism group does not. These results suggest that multisensory integration of simple information, void of social content or complexity, is altered in autism. Individuals with autism may not benefit from the advantage conferred by multisensory stimulation to the same extent as TD individuals. Altered MSI for simple, non-social information may have cascading effects on more complex perceptual processes related to language and behaviour in autism.

New possibilities of using information from satellite photos and camera records to analyze traffic events

In the analysis of road accidents (collisions and accidents), the reconstructions are based on various information gathered in the process of preparing the proper documentation. So far, this information included: circumstances given in the explanations or testimonies of participants and witnesses of the incident, material evidence located in place of the incident, injuries of the victims taking part, the image of the vehicles ‘damage. Currently, due to development of a new technology, new information is available, such as: satellite images of the event, as well as video recording from cameras placed inside vehicles or other cameras located on the objects next to the scene of the incident (e.x.: monitoring). The article describes few examples how the usage of new technology and information obtained influences the analysis of road accidents, e.g. determining the duration of “state of threat” or the actual reaction time of the driver.

Mental Fatigue Estimation Using EEG in a Vigilance Task and Resting States.

Mental fatigue induced by long time mental work can cause deterioration in task performance and increase the risk of accidents. Recently, electroencephalogram (EEG)-based monitoring of mental fatigue has received increasing attention in the field of brain-computer interfaces (BCI). This study aims to employ EEG signals to measure the mental fatigue level by estimating reaction time (RT) in a psychomotor vigilance task (PVT). In a 36-hour sleep deprivation experiment, EEG data from 18 subjects were recorded every four hours in nine blocks, each consisting of three tasks: a 6-minute PVT task and two 3-minute resting states (eyes closed and eyes open). The mean RT in the PVT task showed a generally increasing trend during the 36-hour awake period, reflecting the increase of fatigue over time. For each task, multiple EEG features were extracted and selected to better estimate RT using a multiple linear regression (MLR) method. The correlation between predicted RT and actual RT was evaluated using a leave-one-subject-out (LOSO) validation strategy. After parameter optimization, EEG data from the PVT task obtained a mean correlation coefficient of $0.81 \pm 0.16$ across all subjects. Resting-state EEG data showed lower correlations (eyes-closed: $0.65 \pm 0.20$, eyes-open: $0.50 \pm 0.30)$ partially due to the involvement of shorter data lengths. These results demonstrate the feasibility and robustness of the EEG-based fatigue monitoring method, which could be potential for applications in operational environments.

Human balancing on rolling balance board in the frontal plane

Human balancing on rolling balance board in the frontal plane is analyzed using a two DoF mechanical model, where the human body is modeled by a four-bar linkage mechanism and the geometry of the balance board can be adjusted. Human nervous system is assumed to employ a proportional-derivative controller with constant feedback delay identical to the human reaction time. It is shown that a critical feedback delay exists for each geometry of the balance board. If the reaction delay is larger than the critical one, then there are no stabilizing control gains. A numerical algorithm was developed in order to find the critical time delay based on the mechanical model. The numerical results are compared with real balancing trials, and the corresponding feedback delays in the model are compared to the results of actual reaction time tests.

Non-parametric Algorithm to Isolate Chunks in Response Sequences.

Chunking consists in grouping items of a sequence into small clusters, named chunks, with the assumed goal of lessening working memory load. Despite extensive research, the current methods used to detect chunks, and to identify different chunking strategies, remain discordant and difficult to implement. Here, we propose a simple and reliable method to identify chunks in a sequence and to determine their stability across blocks. This algorithm is based on a ranking method and its major novelty is that it provides concomitantly both the features of individual chunk in a given sequence, and an overall index that quantifies the chunking pattern consistency across sequences. The analysis of simulated data confirmed the validity of our method in different conditions of noise, chunk lengths and chunk numbers; moreover, we found that this algorithm was particularly efficient in the noise range observed in real data, provided that at least 4 sequence repetitions were included in each experimental block. Furthermore, we applied this algorithm to actual reaction time series gathered from 3 published experiments and were able to confirm the findings obtained in the original reports. In conclusion, this novel algorithm is easy to implement, is robust to outliers and provides concurrent and reliable estimation of chunk position and chunking dynamics, making it useful to study both sequence-specific and general chunking effects. The algorithm is available at: https://github.com/artipago/Non-parametric-algorithm-to-isolate-chunks-in-response-sequences.

Sensitivity analysis on new simulation-based conflict metrics

The Conflict Propensity Metric (CPM) and the Aggregate Conflict Propensity Metric (ACPM) are two simulation-based conflict metrics recently proposed as surrogate safety measures. The two metrics are derived through a stochastic process incorporating distributions of driver reaction time (RT) and vehicle maximum braking rates (MABR). This paper presents sensitivity analyses on the two metrics, by altering the parameters (i.e. mean and standard deviation) of RT distributions. Both RT mean and standard deviation affect the estimates of CPM for the three conflict types examined here (i.e. crossing, rear-end and lane change), and the impacts vary by conflict types, indicating the need of carefully evaluating and considering both RT distributions and conflict types when developing simulation-based conflict metrics. A sensitivity analysis based on field data showed that different RT distributions have an impact on ACPM and could affect the reliability of ACPM in identifying relative safety and its correlation with actual crashes. The analysis here identified the potential existence of different “realistic” RT distributions for different conflict types and the suggested values are considered reasonable or consistent with prior findings. ACPM has proved to have potential to further improve its accuracy using more suitable RT distributions. However, dedicated RT distributions for specific conflict types are lacking, especially a joint RT distribution conditional various factors, impeding the improvement of ACPM. In general, sensitivity analyses have shown the strength of the process of deriving CPM and ACPM by providing reasonable findings, as well as pointing out interesting and important future research directions, such as finding actual RT distributions for different conflict types.

Titration of Limited Hold to Comparison in Conditional Discrimination Training and Stimulus Equivalence Testing

Reaction time (RT), thought to be important for acquiring a full understanding of the establishment of equivalence classes, has been reported in a number of studies within the area of stimulus equivalence research. In this study, we trained 3 classes of potentially 3 members, with arbitrary stimuli in a one- to-many training structure in 5 adult participants, using a touch screen and software-based recordings. After training the conditional relations, a limited hold (LH) was calculated for each of the 5 participants based on actual RT. Training with a titrating LH in 100-ms steps was conducted until all the participants responded within 1.2 s. Finally, programmed consequences were thinned before testing. We arranged an LH of 2.5 s during the testing for emergent relations. 1 of the 5 participants was found to demonstrate stimulus equivalence. The pattern of increasing RT from baseline trials to symmetry and equivalence test trials was not found.

Subjective reports of stimulus, response, and decision times in speeded tasks: How accurate are decision time reports?

Four experiments examined how accurately participants can report the times of their own decisions. Within an auditory reaction time (RT) task, participants reported the time at which (a) the tone was presented, (b) they decided on the response, or (c) the response key was pressed. Decision time reports were checked for plausibility against the actual RTs, and we compared the effects of experimental manipulations on these two measures to see whether the reported decision times showed appropriate effects. In addition, we estimated the amount of error associated with individual decision time reports by checking how often participants' decision time reports were implausibly early (i.e., before stimulus onset) or late (i.e., after response), and by using several quantitative models. Overall, the results suggest that decision time reports are not very accurate but they may be usable for some purposes.

A predictive kinetic study of lipase-catalyzed ethanolysis reactions for the optimal reutilization of the biocatalyst

A new application of the kinetics modeling for the optimal reutilization of an immobilized lipase from Pseudomonas cepacia in the ethanolysis of vegetable oils is presented. Two different rate expressions were explored to take into account the lipase inactivation. The methodology developed is based on the utilization of the pseudo reaction time that indicates how much longer the reaction mixture must remain in the reactor (actual reaction time) to achieve the conversion that would have been achieved if the enzyme had not been partially deactivated (pseudo reaction time). An initial batch of lipase was employed in 15 consecutive trials in order to quantitatively characterize the process over a range of lipase activity and to validate the ability of the methodology utilized to describe the kinetics of both ethanolysis and deactivation. Then, the model developed was employed to predict the time necessary to attain a desired conversion in subsequent reaction cycles in both, trials with the same batch of lipase with different degree of inactivation, and trials with a new batch of immobilized lipase with different specific activity. The reaction times predicted to attain a 38% disappearance of glyceryl ester bonds were experimentally verified by carrying out the corresponding ethanolysis reactions of 100 g of sunflower oil. The agreement between the desired and experimentally attained conversions achieved validates the methodology developed to estimate reaction time in lipase-catalyzed ethanolysis reactions.

Micromixing crowded biological agents by folding slugs through pillars

Abstract The natural state of the interior of a living cell is extremely dense with numerous molecules packed into a tiny amount of space. Such a physiological environment is known as “crowded” and can exert profound effects on the thermodynamic and kinetic properties of the molecules. In general most biochemical experiments involve low molecular concentrations and in the process, underestimate many reaction rates. This paper reports work on a microfluidic system fabricated using polydimethylsiloxane, and relied on chaotic advection to rapidly mix crowded biological solutions that have been isolated in droplets (slugs). By forcing the slugs through a pillar matrix, the slugs were compelled to stretch and fold repeatedly, creating unsteady fluid flows that rapidly mixed the slug contents in tens of milliseconds at Reynolds number in the order of 10−3. Both straight and serpentine channels containing pillars were used for mixing the slug contents. Our results suggested that the pillars generated a significant amount of interfacial stresses on the slugs and in the process induced rapid mixing. This makes the system suitable for the study of reaction kinetics, which requires reactants to be mixed faster than the actual reaction time itself.

Studies on the Effects of Operating Parameters in Manufacturing C/SiC Composites by the Pulse-CVI

Manufacturing C/SiC composites from the reaction of methyltrichlorosilane (MTS) and hydrogen by the pulse CVI (Chemical Vapor Infiltration) was studied. In the pulse CVI, three steps such as evacuation of the reactor (te), injection of reactant gases (ti), and infiltration and deposition reaction during a hold-on period (tr) were repeated. Effects of each step were studied by changing the duration of each step.As the evacuation time increased and the reaction time decreased during the same total actual reaction time, the amount of deposition in the preform increased. Effects of the changes of evacuation time were greater than those of reaction time. The same results were confirmed with the thermal analysis data, porosimeter, and SEM.

Anticipatory postural adjustments during self-paced and reaction-time movements.

We studied the changes in the anticipatory postural adjustments (APAs), associated with dropping a load from extended arms and during fast bilateral shoulder flexion movements, when movements were performed in a self-paced manner and under a simple reaction-time instruction. The latter instruction applied time pressure and did not allow the regular pattern of APAs to be used. In particular, the following questions were asked: (1) are there changes in the relative timing of APAs under the reaction time condition; (2) are changes in the relative timing of APAs associated with changes in APAs themselves; (3) can different postural strategies be used to maintain stability under self-paced and reaction time conditions; and (4) are changes in APAs related to actual reaction time or to a change in the instruction? In particular, under reaction-time conditions, APAs occurred later in time, typically simultaneously with the initiation of the focal movement. Additional changes in electromyographic (EMG) patterns in postural muscles included an increase in the amplitude of EMG bursts and "speeding-up" some of the tri-phasic patterns in postural dorsal-ventral muscle pairs. This was accompanied by a smaller early shift of the center of pressure followed by its more rapid delayed displacement. There was considerable variability in the changes of EMG and dynamic characteristics across subjects. Some of the changes in the EMG patterns in postural muscles depended on actual reaction time, while others were related to a change in the instruction and occurred even if actual reaction times were long enough to allow for the typical self-paced APA patterns to occur. These findings can be interpreted as supporting the parallel control hypothesis for the focal movement and postural adjustments. Alternatively, they can be interpreted within a framework that implies the generation of a single control function, which is transformed into two components, one directed at the focal muscles/joints and the other directed at postural muscles/joints.

Eisen-Bestimmung mit dem CentrifiChem System

The determination of iron was adapted to the CentrifiChem System. The iron bound to transferrin is freed with a detergent, reduced to Fe++ with sodium dithionite, and determined with bathophenanthroline disulphonate. The operation consists of one run for the blank value and one analytical run. Although the actual reaction time is extremely short, a reaction time of 8--10 min is recommended for both the blank value and the analysis. This ensures adequate clearing during centrifugation under the influence of Teepol. 2 times 100 mul serum are required, and 80 determinations per hour are possible.