Bimodal Shape Research Articles

Analysis of Information Search around the Time of Childbirth: Estimating Probability Distributions of Search Dates via Mathematical Optimization

Many mothers have considerable anxiety about pregnancy, childbirth, and childcare. For such mothers, searching for information on the Internet is an effective means of dissolving their anxieties. We consider the problem of estimating, for each search word, a distribution of search dates with respect to children’s birth dates. Most of the empirical distributions have unimodal or bimodal shapes, and some of them are asymmetric about extremal points and rise or fall sharply. We propose nonparametric estimation methods based on mathematical optimization models for such probability distributions. Our unimodal and bimodal optimization models automatically estimate the optimal extremal points and can be extended to multimodal distributions. These models are formulated as mixed-integer convex quadratic optimization problems, which can be solved exactly using optimization software. Experimental results using real-world and synthetic datasets demonstrate that our methods are effective by comparison to conventional moving average and kernel estimation methods.

First report and molecular analysis of population stability of the invasive Gulf wedge clam, Rangia cuneata (G.B. Sowerby I, 1832) in the Pomerian Bay (Southern Baltic Sea)

Native to the Gulf of Mexico, Gulf wedge clam (Rangia cuneata) has been successfully invading Baltic Sea since first introduction with ballast waters in 2010. In this study, we report new occurrence sites in the Pomeranian Bay and in the brackish water of the Szczecin Lagoon. We aimed to describe the structure and stability of the new population of Gulf wedge clam using ecological indicators (i.e. condition index, length-at-age) and a molecular approach targeting first cytochrome oxidase subunit (COX1) fragments. The study showed an age structure dominated by adult clams (aged 4+), rather than the often reported juveniles. We found that the condition of the R. cuneata population in the Pomeranian Bay is characteristic of the expansion model after bottleneck. Genetic analyses indicated low nucleotide (π = 0.00387 ± 0.00012) and haplotype (h = 0.79 ± 0.018) diversity. A haplotype network inferred by a median-joining method showed lack of haplotype H6 (Chesapeake Bay, NW Atlantic) and numerous individuals with haplotype H1 (Gulf of Mexico). Demographic parameters (non-significant Tajima’s D = 2.058, Fu’s Fs = 2.298, Fu and Li’s D* = 1.195, and significant Fu and Li’s F test = 1.757) suggested that the population underwent a moderate population bottleneck, while analysis of mismatch distribution showed a bimodal shape which may imply population admixture as a consequence of “allelic surfing”. Moreover, we concluded that R. cuneata has successfully invaded the basin of the LNG terminal, although our study proved non-linear growth of this species.

Unsaturated characteristics and transport of hydrated chromium ore processing residue

A mining tail cover system for controlling toxic substances (e.g. chromium (VI) (Cr6+)) in chromium ore processing residue (COPR) requires unsaturated transport modelling with inputs of water retention curves (WRCs) to evaluate the system. This study experimentally characterised the unsaturated properties of unweathered grey-black (GB) and weathered hard-brown (HB) COPR before and after hydration associated with mineralogical changes and estimated chromium transport by employing numerical modelling with the properties. X-ray diffraction (XRD) tests were also performed before and after testing to quantify the mineralogical compounds of materials. The XRD results showed that the brownmillerite decreased with the degree of the hydration. The relationship between the fitting parameters of WRC models and variables, such as the degree of hydration and specific gravity, was investigated. The WRC of GB COPR shows a bimodal shape because of the hydration process during the test. The hydration process transformed the chemical and mineralogical composition of GB COPR, thus influencing its WRC characteristics. Numerical simulations parameterised by WRC properties were conducted to compare unsaturated transport between GB and HB COPR through a sandy cover. HB COPR had a longer transportation time than GB COPR, revealing the importance of considering water retention characteristics in remediation plans.

Rear-End Impacts - Part 1: Field and Test Data Analysis of Crash Characteristics

<div class="section abstract"><div class="htmlview paragraph">Prior to developing or modifying the protocol of a performance evaluation test, it is important to identify field relevant conditions. The objective of this study was to assess the distribution of selected crash variables from rear crash field collisions involving modern vehicles. The number of exposed and serious-to-fatally injured non-ejected occupants was determined in 2008+ model year (MY) vehicles using the NASS-CDS and CISS databases. Selected crash variables were assessed for rear crashes, including severity (delta V), impact location, struck vehicle type, and striking objects. In addition, 15 EDRs were collected from 2017 to 2019 CISS cases involving 2008+ MY light vehicles with a rear delta V ranging from 32 to 48 km/h. Ten rear crash tests were also investigated to identify pulse characteristics in rear crashes. The tests included five vehicle-to-vehicle crash tests and five FMVSS 301R barrier tests matching the struck vehicle.</div><div class="htmlview paragraph">The analysis of NASS-CDS and CISS data indicates that more than 50% of exposed (MAIS 0+F) occupants were involved in a rear crash with a distributed impact and with no over-ride or under-ride. More than 93% were with a 6 o’clock PDOF. The average rear delta V was 21.3 ± 1.2 km/h (median 18.2, 90th CI 9.7-33.4) in the exposed (MAIS 0+F) occupant sample. For serious-to-fatally (MAIS 3+F) injured occupants, more than 88% were in a fully distributed rear impact and in 6 o’clock PDOF; 10.7% were in offset impacts and less than 1% were in narrow impacts. The average delta V was 35.9 ± 5.2 km/h (median 24.4, 90th CI 16.2-58.3) for serious-to-fatally (MAIS 3+F) injured occupants.</div><div class="htmlview paragraph">The results from the field data suggest that rear impacts with a delta V of 34-38 km/h and a 6 o’clock PDOF are representative of the average rear-crash scenario causing serious-to-fatal injury. Compared to the exposed occupants in the field data analysis, a 40 km/h rear sled is more than 1.9-times more severe than the average rear impact crash severity in terms of delta V and 4.4-times more severe in terms of crash energy. It is 1.11-times more severe than the average delta V for the serious-to-fatally (MAIS 3+F) injured occupant. It accounts for more than 90% of all occupants with injury (MAIS 1+F).</div><div class="htmlview paragraph">EDR data was helpful in accessing overall delta-V and impact duration information. For example, the average delta V in the EDRs included in the analysis was 38.7 ± 7.6 km/h and the average pulse duration was 129.6 ± 24.3 ms. Instrumentation data from crash tests provided more refined information for a detailed analysis of pulse characteristics.</div><div class="htmlview paragraph">The acceleration data obtained from the five vehicle-to-vehicle crash tests was investigated and compared to matched FMVSS 301 tests with the same struck vehicle. The data was scaled to a 40 km/h delta V pulse for comparison purposes. Bi-modal pulse shape characteristics were observed. The peak acceleration averaged 18.4 g in the vehicle-to-vehicle tests and 21.4 g in the FMVSS 301R tests. The average pulse duration was 147.2 ms and 123.8 respectively.</div><div class="htmlview paragraph">The results from this study suggest that using a 34-40 km/h bimodal-rear pulse with a 130-160 ms duration is representative of a serious real world rear impact.</div></div>

Retracted] Application to Biomedical Data: Using the Topp Leone Inverse Lindley Model

A more flexible two‐parameter model named the Topp Leone inverse Lindley model is investigated. Some basic mathematical properties such as quantile, moments, order statistics, and Rényi entropy of the new distribution are considered. Plot analysis for mean, variance, skewness, and kurtosis is performed. The density of the new model can be right skewed and decreasing with unimodal and bimodal shapes. Also, its hazard rate function can be decreasing and upside‐down. The maximum likelihood (ML) estimation method is used to estimate the parameters of the distribution. The simulation study is executed to investigate the effectiveness of the estimates. The potential of the distribution is demonstrated through the application of the real biomedical dataset.

A Logistic Trigonometric Generalized Class of Distribution Characteristics, Applications, and Simulations

We propose a trigonometric generalizer/generator of distributions utilizing the quantile function of modified standard Cauchy distribution and construct a logistic‐based new G‐class disbursing cotangent function. Significant mathematical characteristics and special models are derived. New mathematical transformations and extended models are also proposed. A two‐parameter model logistic cotangent Weibull (LCW) is developed and discussed in detail. The beauty and importance of the proposed model are that its hazard rate exhibits all monotone and non‐monotone shapes while the density exhibits unimodal and bimodal (symmetrical, right‐skewed, and decreasing) shapes. For parametric estimation, the maximum likelihood approach is used, and simulation analysis is performed to ensure that the estimates are asymptotic. The importance of the proposed trigonometric generalizer, G class, and model is proved via two applications focused on survival and failure datasets whose results attested the distinct better fit, wider flexibility, and greater capability than existing and well‐known competing models. The authors thought that the suggested class and models would appeal to a broader audience of professionals working in reliability analysis, actuarial and financial sciences, and lifetime data and analysis.

Dynamic Mechanical Characteristics of Impact Rock under the Combined Action of Different Constant Temperatures and Static and Dynamic Loads

The complex mechanical environment of deep coal and rock masses leads to obvious changes on their dynamic mechanical properties. However, there are few reports on the dynamic mechanical properties of rocks under the combined action of medium temperature (normal temperature ∼100°C) and static and dynamic loads. In this paper, a dynamic load and temperature combined action Hopkinson pressure bar experimental system is used to experimentally study the impact type of a fine sandstone under temperature conditions of 18°C, 40°C, 60°C, 80°C, and 100°C, an axial static load of 3 MPa, a gas chamber pressure of 0.06 MPa, and a constant temperature time of 4 h. The dynamic characteristics of the change law of the fine sandstone and the energy dissipation characteristics of the load process are analyzed, and the characteristic law of the fine sandstone surface response is analyzed using digital image correlation technology. Our results indicate the following. (1) Under conditions in which the other experimental conditions remain unchanged, the dynamic stress-strain of the fine sandstone presents a bimodal shape with a “rebound” phenomenon. Increasing temperature causes the peak strength of the fine sandstone to increase; however, the relative strength can increase or decrease. The relative increase in the strength is 1.14 MPa (°C) when the temperature increases from 40°C to 60°C, 0.15 MPa (°C) when the temperature increases from 60°C to 80°C, and 0.62 MPa (°C) when the temperature increases from 80°C to 100°C. (2) The digital image correlation results show that, under the action of a dynamic load stress wave, the fine sandstone experiences a displacement vector change on the sample surface; furthermore, under the combined action of the temperature and dynamic and static loads, the fine sandstone experiences macroscopic shear failure. The surface strain in the propagation direction of the stress wave is obviously higher and can even reach values of more than 10 times that of the strain in other directions. (3) From the perspective of energy dissipation, the incident energy, reflected energy, and dissipated energy of the fine sandstone under an impact load have the same change law. After being affected by a dynamic load, the energy rapidly increases to a certain value and then remains relatively stable. The transmitted energy is relatively small and can be approximated as a horizontal line. As the temperature increases, the incident energy, reflected energy, and dissipated energy tend to first decrease and then increase, and most of the incident energy in the fine sandstone is dissipated in the form of reflected waves.

Sex-specific bimodal clustering of left ventricular ejection fraction in patients with acute heart failure.

AimsThere is an ongoing discussion whether the categorization of patients with heart failure according to left ventricular ejection fraction (LVEF) is scientifically justified and clinically relevant. Major efforts are directed towards the identification of appropriate cut‐off values to correctly allocate heart failure‐specific pharmacotherapy. Alternatively, an LVEF continuum without definite subgroups is discussed. This study aimed to evaluate the natural distribution of LVEF in patients presenting with acutely decompensated heart failure and to identify potential subgroups of LVEF in male and female patients.Methods and resultsWe identified 470 patients (mean age 75 ± 11 years, n = 137 female) hospitalized for acute heart failure in whom LVEF could be quantified by Simpson's method in an in‐hospital echocardiogram. Non‐parametric modelling revealed a bimodal shape of the LVEF distribution. Parametric modelling identified two clusters suggesting two LVEF peaks with mean (variance) of 61% (9%) and 31% (10%), respectively. Sub‐differentiation by sex revealed a sex‐specific bimodal clustering of LVEF. The respective threshold differentiating between ‘high’ and ‘low’ LVEF was 45% in men and 52% in women.ConclusionsIn patients presenting with acute heart failure, LVEF clustered in two subgroups and exhibited profound sex‐specific distributional differences. These findings might enrich the scientific process to identify distinct subgroups of heart failure patients, which might each benefit from respectively tailored (pharmaco)therapies.

Flexible Power-Normal Models with Applications

The main object of this paper is to propose a new asymmetric model more flexible than the generalized Gaussian model. The probability density function of the new model can assume bimodal or unimodal shapes, and one of the parameters controls the skewness of the model. Three simulation studies are reported and two real data applications illustrate the flexibility of the model compared with traditional proposals in the literature.

Bayesian inference methods to calibrate crowd dynamics models for safety applications

Crowd simulation is a crucial tool to assess risks and engineer crowd safety at events and in built infrastructure. Simulations can be used for what-if studies, for real-time predictions, as well as to develop regulations for crowd safety. A reliable prediction requires a carefully calibrated model. Model parameters are often calibrated as point estimates, single parameter values for which the model evaluation fits given data best. In contrast, Bayesian inference provides a full posterior distribution for the fitted parameters that includes the residual uncertainty after calibration. In this work, we calibrate a microscopic model and an emulator derived from a microscopic model for crowd dynamics using point estimates and Approximate Bayesian Computation. We calibrate on data measuring the flow through a key scenario of crowd safety: a bottleneck. We vary the bottleneck width and demonstrate via three case studies the advantages and shortcomings of the two calibration techniques. In a case with a unimodal posterior, both methods yield similar results. However, one safety-relevant case study, that mimics the dynamics of evacuating people squeezing through an opening, exhibits a faster-is-slower dynamic where multiple free-flow speeds lead to the same flow. In this case, only Bayesian inference reveals the true bimodal shape of the posterior distribution. For multidimensional calibration, we illustrate that Bayesian inference allows accurate calibration by describing parameter relations. We conclude that, in practice, point estimation often seems sufficient, but Bayesian inference methods are necessary to capture important structural information about the uncertain parameters, and thus the physics of safety.

Stochastic bifurcations and its regulation in a Rijke tube model

This paper explores the stochastic dynamics in a Rijke tube model. Dynamical model is established to identify the bifurcation properties of the Rijke tube model. We gain the analytical expression of the local Hopf bifurcation and global saddle-node bifurcation of the limit cycle in the deterministic case. The stationary probability density function (PDF) of the model is attained base on the method of stochastic average in the case of stochasticity. The investigations indicate that the stationary PDF switches from unimodal shape to bimodal one, and then, from bimodal shape to unimodal one again, when noise intensity, fractional order, time delay monotonically increase which is the typical feature of stochastic P-bifurcation. Further, we conclude that the stochastic P-bifurcation can be induced or suppressed by modulating the time delay, the noise intensity, or the fractional order. These findings of the study will be helpful to the theoretical study of thermoacoustic instability and the preliminary design of thermoacoustic devices where thermoacoustic instability is a concern.

Assessment of the vulnerability of road networks to urban waterlogging based on a coupled hydrodynamic model

Waterlogging events in urban areas are becoming increasingly more frequent, which has led to tremendous economic losses. Urban road networks have also suffered heavy interference and destruction due to this type of disaster, and the precise assessment of road network vulnerability is an effective measure by which to reduce losses. Therefore, in this study, an analytical framework for the assessment of the vulnerability of road networks to urban waterlogging was constructed by using a coupled hydrodynamic model. The rainfall patterns in the study area were detected, and their impacts on vulnerability are discussed. The results show that rainfall events with unimodal, bimodal, and uniform shape patterns respectively account for 68.08%, 31.46%, and 0.47% of the total number of events considered in this study. The coupled hydrodynamic model used in this study is found to have satisfactory applicability for waterlogging simulation. Rainfall with a unimodal shape is found to have the greatest impact on the vulnerability of road networks, while that with a uniform shape has the least. Among the unimodal shapes, Mode II (late peak) and Mode III (middle peak) are the most dangerous.

Emission characteristic of non-road mobile machinery using a catalysed diesel particle filter with different catalyst loadings under actual operating conditions

The real-world gaseous and particulate emission characteristics of an agricultural tractor retrofitted with a catalysed diesel particulate filter (CDPF) with different catalyst loadings were investigated. The tests were carried out using a portable emission measurement system (PEMS) under idling, running and working conditions. The results showed that the emissions of the tractor strongly depended on the operating conditions. From idling to running then to working condition, the emission rates increased but emission factors based on fuel consumption decreased, and the proportion of nucleation particles and geometric mean diameter presented a slight downward trend. The reduction effect of CDPF on the CO and total hydrocarbon (THC) improved from idling to running then to working condition, and it was enhanced by increasing catalyst loading. The particle number (PN) and particle mass (PM) reduction performance of CDPF was less affected by operating condition but enhanced with the increase of the catalyst loading. After the tractor was equipped with the CDPF, the particle size distribution maintained a bimodal shape, but the decrease of nucleation particles was significantly higher than that of accumulation particles, causing a decrease in the nucleation particles proportion and a shift of the peak towards smaller particle size. With the increase of the CDPF catalyst loading, the proportion of the accumulation particles increased, and the geometric mean particle size also increased. The findings of this paper can provide scientific references to design and optimize CDPF for non-road mobile machinery to achieve clean emissions.

Effects of diesel from direct and indirect coal liquefaction on combustion and emissions in a six-cylinder turbocharged diesel engine

The aim of this study is to evaluate the effects of diesel from direct coal liquefaction (DDCL) and diesel from indirect coal liquefaction (DICL) on combustion and emissions. A six-cylinder turbocharged diesel engine fueled with DDCL, DICL, petroleum diesel (PD), 58% DDCL, and 42% DICL blended by volume (BD58) is used. The experiments are carried out at 1400 and 2300rpm engine speeds and various engine loads (10%, 25%, 50%, 75%, and 90% of the full-load). The results show that the brake thermal efficiency (BTE) of PD was higher than that of CTL (the maximum difference was 2%) at medium and high loads. At 10% load of 1400 rpm, the CO, HC and formaldehyde emissions of DDCL are 88.9%, 44.3% and 26.5% higher than those of PD respectively, and the CO, HC, and formaldehyde emissions of DICL are 30.1%, 15.3%, and 15.2% lower than those of PD. The differences among four fuels decrease rapidly with the increase of load. The NOX emissions of PD are the highest due to high nitrogen content (102.3 μg/g) and low hydrogen-carbon (H/C) ratio. The fuel with higher cetane number has less formaldehyde emission at low loads, while the fuel with lower H/C has less formaldehyde emission at high loads. The particle size distribution shows a bimodal shape at different loads and the peak particle size of accumulation mode and nucleation mode all increases with the increase of load. The particulate emission of different fuels from high to low is the order of PD > DDCL > BD58 > DICL. In addition, the emissions of polycyclic aromatic hydrocarbons (PAHs) and toxicity equivalent (TE) of PD are highest at all loads. The proportion of soluble organic fractions (SOF) from DDCL, DICL, and BD58 is higher than that of PD.

Bimodal probability distributions decoded from human visual cortex reflect perception

How do humans infer an object’s direction of motion from noisy sensory input? We hypothesized that observers utilize not only motion but also orientation information in their inferences, capitalizing on “streaks” created by moving objects (see also Geisler, 1999, Nature). We implemented this hypothesis in an ideal (Bayesian) observer framework, in which an observer’s knowledge is quantified using probability distributions. This led to several predictions that we tested using psychophysics and fMRI. Participants viewed dots moving coherently in a random direction and then reported the perceived direction of motion. Using a probabilistic pattern-based analysis (cf. van Bergen, Ma, Pratte & Jehee, 2015, Nature Neuroscience), we decoded the probability distribution of motion direction from activity patterns in visual areas V1-V4, and hMT+. Corroborating the predictions of the Bayesian observer model, we found that 1) probability distributions decoded from cortical activity had a characteristic bimodal shape, consistent with the notion that orientation might provide an important cue to the direction of motion. 2) The widths and 3) locations of the two peaks of the decoded probability distributions predicted, respectively, trial-by-trial variability in the participants’ behavioral responses, and the magnitude and direction of their behavioral errors. Finally, (4) in a follow-up behavioral experiment, analysis of the behavioral response distribution revealed a similar bimodal pattern, with one peak roughly centered at 0° and the other at 180° with respect to the true motion direction. Thus, observers sometimes perceived the stimulus as if it moved in a direction opposite to its true direction of motion, as predicted by the model. Together, these results suggest that human observers use not only motion, but also orientation information in their judgments of a moving stimulus, and moreover reveal the neural basis of the inference process involved.

The Study of a Wealth Distribution Model with a Linear Collision Kernel

The wealth substitution rate, which describes the substitution relationship between agents’ investment in wealth, is introduced into the collision kernel of the Boltzmann equation to study wealth distribution. Using the continuous trading limit, the Fokker–Planck equation is derived and the steady-state solution is obtained. The results show that the inequality of wealth distribution decreases as the wealth substitution rate increases under certain assumptions. The wealth distribution has a bimodal shape if the wealth substitution rate does not equal one.

Characterization of a seasonally snow-covered evergreen forest ecosystem

It remains challenging to interpret seasonal profile of vegetation dynamics from empirical indices NDVI and EVI for boreal forests due to confounding impacts of snow, soil and snowmelt in winter and spring. This work aims to characterize the seasonally snow-covered Howland boreal forest ecosystem in Maine, USA with the Moderate Resolution Imaging Spectrometer (MODIS) images. Vegetation cover fraction (VGCF), fractional absorption of photosynthetically active radiation (fAPAR) by all canopy components (fAPARcanopy), fAPAR by canopy chlorophyll (fAPARchl) and fAPAR by canopy non-chlorophyll components (fAPARnon-chl) were extracted from MODIS images in multiple years (2001 - 2014). Snow exposed during December to April. Top of canopy viewable snow cover fraction in April of multiple years varied between 0.02 and 0.16 (0.06 ± 0.04). Seasonal VGCF and fAPARcanopy showed a summer plateau (VGCF: 0.97 ± 0.01; fAPARcanopy: 0.90 ± 0.01). Both seasonal fAPARchl and fAPARnon-chl changed with time, and seasonal fAPARnon-chl had a bimodal shape. Spring VGCF varied between 0.54 and 0.69 (0.61 ± 0.04). Spring fAPARchl and fAPARnon-chl were 0.22 ± 0.03 and 0.21 ± 0.02, respectively. Peak summer fAPARchl was 0.58 ± 0.02. The lowest summer fAPARnon-chl was 0.32 ± 0.02. Replacing fAPARcanopy with fAPARchl to simulate boreal forest ecosystem gross primary production (GPP) could reduce uncertainties in GPP simulations.

Analysis of aerosol optical and microphysical characteristics over Yinchuan (China) in 2019

ABSTRACT Using the European Skynet Radiometers (ESR).pack algorithm and data obtained in the Yinchuan (China) area in 2019 using a Cimel CE-318 sun photometer, this study inverted aerosol parameters such as optical depth, volume size distribution, phase function and single scattering albedo. Additionally, the HYSPLIT backward-trajectory model was used to establish the source characteristics of the aerosols in each season and to determine their climatic impact. Results showed that aerosol optical depth had an evident seasonal trend of change, reaching a maximum (minimum) in spring (summer), and continue to rise in autumn and winter. The relationship between aerosol optical depth and the Ångstrom exponent in each season showed that the types of aerosol in the Yinchuan area changed little between seasons, comprising mainly mixed aerosols followed by continental clean aerosols. The volume size distribution presented a bimodal shape, reflecting that the peak of fine (coarse) particles increased significantly on hazy (dusty) days. Moreover, the biggest change in the trend of the volume size distribution was in summer. The phase function distribution revealed evident side and back scattering by dust aerosol particles. Change in the single scattering albedo on both hazy and dusty days was reasonably stable, but the value on dusty days was larger than that on hazy days. The single scattering albedo was largest (smallest) in summer (winter). Moreover, the clustering results of wind field trajectories show that the Yinchuan area is greatly affected by the wind field from the north throughout the year. The findings of this study have particular importance regarding research into the characteristics of aerosol parameters using CE-318 sun photometers at sites that are not part of the global AErosol RObotic NETwork (AERONET) project.

Characteristics of movable fluids in tight sandstone reservoir and its influencing factors: a case study of Chang 7 reservoir in the Southwestern of Ordos Basin

Aiming at the problem of complicated occurrence and flow state of the fluid in tight sandstone reservoir, this paper takes Chang 7 reservoirs in Southwestern of Ordos Basin as an example to analyze the occurrence characteristics of movable fluids by nuclear magnetic resonance experiment, while takes a series of microscopic experiments to analyze the influencing factors of difference of movable fluids. The results show that the T2 spectrum curves of fluid-saturated samples from Chang 7 reservoirs in the study area are dominated by the unimodal shape and the left-high-peak-right-low-peak bimodal shape. After centrifugation, the T2 spectrum curves are dominated by the left-high-peak-right-low-peak bimodal shape. The average movable fluid saturation is 33.27%, and the average T2 cutoff value is 13.61 ms. The movable fluids are mainly distributed in medium and large pores, and a small amount is distributed in small pores. The occurrence characteristics of movable fluids in tight reservoirs are complex and not controlled by a single factor. The size of throats and the connectivity of pore-throat have obvious effects on the saturation of movable fluids. The small size of throats and poor connectivity of pore-throat in tight reservoirs not only restrict the fluids in micropores, but also make the fluids in macropores difficult to flow under the control of small throats. The development of clay minerals will make the pore throats smaller, more complex and have poorer connectivity, and increase the fluid seepage resistance. On the other hand, it will make the specific surface area larger, which will cause a large number of fluids adsorbed on the clay surface and difficult to flow, resulting in the reduction of movable fluid saturation.

Qualitative speed-accuracy tradeoff effects can be explained by a diffusion/fast-guess mixture model

Rafiei and Rahnev (2021) presented an analysis of an experiment in which they manipulated speed-accuracy stress and stimulus contrast in an orientation discrimination task. They argued that the standard diffusion model could not account for the patterns of data their experiment produced. However, their experiment encouraged and produced fast guesses in the higher speed-stress conditions. These fast guesses are responses with chance accuracy and response times (RTs) less than 300 ms. We developed a simple mixture model in which fast guesses were represented by a simple normal distribution with fixed mean and standard deviation and other responses by the standard diffusion process. The model fit the whole pattern of accuracy and RTs as a function of speed/accuracy stress and stimulus contrast, including the sometimes bimodal shapes of RT distributions. In the model, speed-accuracy stress affected some model parameters while stimulus contrast affected a different one showing selective influence. Rafiei and Rahnev’s failure to fit the diffusion model was the result of driving subjects to fast guess in their experiment.