Dynamic Criteria Research Articles

Modeling and Simulation Analysis for Urban Rail Transit Hub

Urban rail transit has become the main mode to ease traffic congestion, and urban rail transit hub is the most important area for passenger flow distribution in urban rail transit system. Study on the method of simulation and dynamic evaluation of urban rail transit hub has an important significance for train scheduling, operation organization and risk prevention under the viewpoint of traffic safety and service level. This paper analyzed the system characteristics of urban rail transit hub, proposed agent-based modeling and simulation design, simulation process based on Anylogic, dynamic evaluation index set and classification criteria. Furthermore, Beijing South Subway Station was selected for case study, simulation models which included hub simulation model, passenger flow simulation model and train simulation model were built, and experiment results showed that simulation models had a good performance, which was accordant with the reality scene, simulation error was 0.027. Meanwhile, dynamic evaluation which included distribution efficiency, dynamic service level and emergency capacity during the operation period was researched, and optimizing suggestion was proposed, which could provide the beneficial reference for traffic managers.

Insights into high-entropy material synthesis dynamics criteria based on a thermodynamic framework.

High-entropy materials (HEMs) have attracted increasing research interests owing to their structural diversity and great potential for regulation. Numerous HEMs synthesis criteria have so far been reported but most are based on thermodynamics while a guiding basis for the synthesis of HEMs is lacking, resulting in many synthesis problems. Based on the overall thermodynamic formation criterion of HEMs, this study has explored the principles of the synthesis dynamics required based on this criterion and the influence of different synthesis kinetic rates on the final products of the reaction, filling the gap suggesting that thermodynamic criteria cannot guide the specific process changes. This will effectively provide more specific guidelines for the top-level design of material synthesis. By considering various aspects of HEMs synthesis criteria, new technologies suitable for high-performance HEMs catalysts were extracted. Also, the physical and chemical characteristics of the HEMs obtained from actual synthesis can be predicted in a better way, playing an important role in the personalized customization of HEMs with specific performance. Future development directions of HEMs synthesis were prospected for possible prediction and customization of HEMs catalysts with high performance.

The denervation or activation of renal sympathetic nerve and renal blood flow.

The denervation or activation of the sympathetic nerve in the kidney can affect renal hemodynamics. The sympathetic nervous system regulates the physiological functions of the kidneys. Stimulation of sympathetic efferent nerves affects various parameters related to renal hemodynamics, including sodium excretion, renin secretion, and renal blood flow (RBF). Hence, renal sympathetic fibers may also play an essential role in regulating systemic vascular resistance and controlling blood pressure. In the absence of renal nerves, the hemodynamics response to stimuli is negligible or absent. The effect of renal sympathetic denervation on RBF is dependent on several factors such as interspecies differences, the basic level of nerve activity in the vessels or local density of adrenergic receptor in the vascular bed. The role of renal denervation has been investigated therapeutically in hypertension and related disorders. Hence, the dynamic impact of renal nerves on RBF enables using RBF dynamic criteria as a marker for renal denervation therapy.

Evaluating Dynamic Stall-Onset Criteria for Mixed and Trailing-Edge Stall

We evaluate two leading-edge-based dynamic stall-onset criteria (namely, the maximum magnitudes of the leading-edge suction parameter and the boundary enstrophy flux) for mixed and trailing-edge stall. These criteria have been shown to successfully predict the onset of leading-edge stall at Reynolds numbers of , where the leading-edge suction drops abruptly. However, for mixed/trailing-edge stall, leading-edge suction tends to persist even when there is significant trailing-edge reversed flow and stall is underway, necessitating further investigation into the effectiveness of these criteria. Using wall-resolved large-eddy simulations and the unsteady Reynolds-averaged Navier–Stokes method, we simulate one leading-edge stall and three mixed/trailing-edge stall cases at Reynolds numbers of and . We contrast the progression of flow features such as trailing-edge separation and vortex formation across different stall types and evaluate the stall-onset criteria relative to critical points in the flow. We find that the criteria nearly coincide with the instance of leading-edge suction collapse and are reached in advance of dynamic stall vortex formation and lift stall for all four cases. We conclude that the two criteria effectively signal dynamic stall onset in cases where the dynamic stall vortex plays a prominent role.

Investigation of Dynamic Characteristics Experiments and Stability Evaluation Criterion of Space Ball Bearing Cage

The operation stability of the oil-impregnated cage, which serves as the lubrication and operation core of space ball bearings, is linked to the stability of the bearing dynamic friction moment. A cage dynamic characteristics test rig based on a high-speed camera system is created in this study to achieve synchronous monitoring of the cage centroid trajectory and bearing dynamic friction torque without changing the bearing structure. The centroid trajectory of the cage is separated into aggregation and discrete areas based on the distribution density of centroid trajectory points. To establish the mapping relationship between the shape and fluctuation of the cage centroid trajectory and the stationarity of the bearing dynamic friction moment, a new characteristic quantity, centroid trajectory fluctuation ratio (the ratio of the distance between the track points in the discrete area and the boundary of the aggregation area to the average width of the aggregation area), is adopted. In addition, a criterion based on the distribution density of the centroid trajectory points is proposed for evaluating the cage's operation stability. The findings of the study led to two primary conclusions: (1) The sudden jump of bearing dynamic friction torque is caused by the fluctuation of the cage centroid trajectory, which is independent of the trajectory shape. (2) The fluctuation ratio of centroid trajectory might effectively reflect the operation stability of the cage.

MULTISEMIOTIC PATTERNS OF EMOTIVE MEANING-MAKING IN FILM

The aim of the article is to highlight multisemiotic patterns of emotive meaning making in feature films. The research tasks are: to explore the meaning-making mechanism in a cognitive-pragmatic perspective; to determine the cognitive-semiotic basics of emotive meaning making; and to identify the meaning-making potential of semiotic resources as well as to single out multisemiotic constructive patterns. To reach the aim, we apply an integrative cognitive-pragmatic and cognitive-semiotic approach, which requires the use of discursive and semiotic research methods. In cognitive-pragmatic perspective, we stress the intersubjective interaction of filmmakers and viewers in constructing ‘meaning-in-context’. The cognitive-semiotic vantage point emphasizes dynamic, enactive, and embodied character of meaningmaking in cinematic discourse. Film is a multimodal and multisemiotic phenomenon, where a synergistic combination of verbal, nonverbal, and cinematic semiotic systems constructs the film meaning through audial and visual modes. These semiotically heterogeneous resources – a verbal language, an image, and specific cinematic signs – are blended to construct emotive meaning; and the configurations of these signs determine particular contextual properties of emotions. In film, emotive meaning emerges at the intersection of audial and visual modes as realized by different semiotic resources. Each semiotic resource contains specific meaningful elements characteristic of a certain semiotic resource. Building on the theory of conceptual integration, we claim that emotive meaning in cinematic discourse is a blend constructed by cross-mapping of information from three input spaces corresponding to verbal, nonverbal, and cinematic semiotic resources. The number of blends can be countless as the process of meaningmaking is dynamic and depends upon the communicative situation. The change of any semiotic element may cause the construction of a new meaning demonstrating the emergent character of meaning-making. In semiotic and pragmatic perspectives, we have singled out the combination of semiotic resources along two main criteria: static and dynamic. The static criterion enables to distinguish patterns by parameters of quantity of semiotic resources in a shot, the quality of emotion in each resource, and their salience in film. The dynamic criterion makes it possible to single out the time patterns due to the appearance of each resource on the screen. Accordingly, we argue that there are eight multimodal patterns of semiotic resource configurations, which construct the emotive meaning in cinematic discourse: three-component and two-component, convergent and divergent, parity and non-parity, and synchronous and consecutive patterns. These patterns demonstrate the paradigmatic regulations of combining semiotic resources in cinematic discourse. The peculiarities of emotive meaning-making are illustrated based on the material of the construction of anger in the American drama film “The Beautiful Boy”. Emotive meaning-making in film occurs in two dimensions: material-perceptual and socio-semiotic, as the emotive meaning can be represented physically on the screen, as well as through the implementation of socio-cultural values.

Study on dynamic mechanical properties and constitutive model of granite under constant strain rate loading

A systemic understanding of the dynamic mechanical properties and dynamic constitutive model of granite is of great significance to the study of natural disaster prevention and protection of granite buildings. In the present study, constant strain rate loading tests of granite specimens under different impact velocities were carried out by using a shop-fabricated cylindrical conical striker and split Hopkinson pressure bar (SHPB) test system. The compressive strength of granite material increases with the strain rate, and therefore, a continuously smooth uniaxial dynamic strength criterion suitable for describing the changes in the dynamic increase factor (DIF) with strain rate was proposed and tested. The granite specimen under impact loading was intact when the strain rate was lower than 80 s−1, cracked when it was 80 to 90 s−1, fractured when it was 90 to 135 s−1, and crushed when it was over 135 s−1. Ultrasonic wave tests were performed to evaluate the damage caused by impact, and the quantitative relationship between the damage value and peak stress was established based on regression analysis. The results showed that the stress threshold causing damage was 50.15 MPa with a corresponding strain rate of 31.7 s−1 and a peak strain of 3670 microstrain. A new constitutive model describing the dynamic mechanical properties of granite was developed based on a nonlinear viscoelastic model (the ZWT model), and the constitutive parameters were then determined. A user-defined material subroutine named VUMAT of ABAQUS finite element software was applied to describe the established constitutive model and simulate the impact process of granite. The results confirmed that the developed constitutive model can well describe the prepeak dynamic mechanical properties of granite under impact compression.

Dynamic Simulation and Parameter Analysis of Harpoon Capturing Space Debris

This paper aims to study the penetration effect of harpoons on space debris to ensure the sustainable development of the space environment and solve the increasingly serious space debris problem. Firstly, a harpoon system was designed to capture space debris. Secondly, based on the Johnson-Cook dynamic constitutive model and fracture failure criterion, the finite element models of aluminum alloy plates were established. Then, the ballistic limit theory for the aluminum alloy target predicted the minimum launch velocity of the harpoon. Finally, the validation experiment was set up to verify the correctness of the model. The results show that the error between the simulation results of the speed for the harpoon embedded in the target and the theoretical results of the ballistic limit is 9.1%, which provides guidance for active space debris removal technology.

Experimental and theoretical study of dynamic mechanical behavior of concrete subjected to triaxial confining and impact loads

Confining stress is a key factor affecting the dynamic mechanical behaviour of concrete. To explore the mechanism of triaxial confining stress on the dynamic compressive properties of concrete, a series of static–dynamic combined compression experiments were performed using three–dimensional Split Hopkinson Pressure Bar equipment. The results show that there is an obvious strain rate effect of concrete under triaxial confining conditions, which is closely associated with the static triaxial confining stress and strain rate of impact loads. The confining stress significantly affects the dynamic response stress (strain) and dynamic stress (strain) along the loading direction. Moreover, the effects would decrease with an increase in the dynamic loading strain rate. Obvious fractures will occur on the concrete surface when the effective dissipated energy ratio exceeds 2.56 J/cm3, which proves that it is suitable to describe the fracture features of concrete under triaxial static–dynamic loads. In this study, a dynamic strength criterion of concrete was proposed for concrete under triaxial dynamic loads. The testing data and reference results matched well with suggested value of the proposed dynamic strength criterion. This can provide the theoretical guidance for concrete engineering construction.

Dynamic Criteria for Physical Modeling of Oil Displacement by Gas Injection

In this work, slim tube displacement tests for minimum miscibility pressure MMP were carried out. Based on the displacement data, the MMP was calculated by statistical regression using linear and quadratic extrapolation with threshold values of 90% and 95% oil recovery as well as the intersection of trend lines for immiscible and miscible displacement regimes. The obtained data show a significant variation in the range of MMP values depending on the calculation method. To clarify the MMP value, an analysis of displacement dynamics was carried out. The ratio of the volume flow rate of reservoir oil to the volume flow rate of the injected gas—flow rates ratio (FFR)—was used as a new parameter. The MMP value calculated from the FRR value extrapolation was determined as 37.09 MPa. According to the results obtained, the proposed methodology based on the displacement dynamics can be useful as a criterion for clarifying the MMP value in slim tube displacement experiments.

Confronting the Ideologies of Assimilation and Neutrality in Writing Program Assessment through Antiracist Dynamic Criteria Mapping

This article contributes to conversations about antiracist writing program assessment, with particular attention to the evaluation of first-year writing samples. In an effort to confront the racist ideologies of assimilation and neutrality, I employed a modified version of dynamic criteria mapping (DCM) that involved surveying students, conducting instructor focus groups, and analyzing writing prompts. The triangulated results informed the development of an assessment tool that was used to examine 89 writing samples. The goal of this assessment was not to produce a set of standards that mirror community values but rather to describe what was happening in the writing program and then use that information to facilitate critical reflection on the ways in which classroom practices align with or depart from the programmatic goal of delivering socially just writing instruction. By sharing my own experiences, I hope to help other writing program administrators (WPAs) develop processes for enacting antiracist writing assessment in their own contexts. I also reflect on the ways my procedure did—and did not—achieve its antiracist goals.

A network-based dynamic criterion for identifying prediction and early diagnosis biomarkers of complex diseases.

Lung adenocarcinoma (LUAD) seriously threatens human health and generally results from dysfunction of relevant module molecules, which dynamically change with time and conditions, rather than that of an individual molecule. In this study, a novel network construction algorithm for identifying early warning network signals (IEWNS) is proposed for improving the performance of LUAD early diagnosis. To this end, we theoretically derived a dynamic criterion, namely, the relationship of variation (RV), to construct dynamic networks. RV infers correlation [Formula: see text] statistics to measure dynamic changes in molecular relationships during the process of disease development. Based on the dynamic networks constructed by IEWNS, network warning signals used to represent the occurrence of LUAD deterioration can be defined without human intervention. IEWNS was employed to perform a comprehensive analysis of gene expression profiles of LUAD from The Cancer Genome Atlas (TCGA) database and the Gene Expression Omnibus (GEO) database. The experimental results suggest that the potential biomarkers selected by IEWNS can facilitate a better understanding of pathogenetic mechanisms and help to achieve effective early diagnosis of LUAD. In conclusion, IEWNS provides novel insight into the initiation and progression of LUAD and helps to define prospective biomarkers for assessing disease deterioration.

Trajectory Generation for Multiprocess Robotic Tasks Based on Nested Dual-Memory Deep Deterministic Policy Gradient

Though there are extensive works on deep reinforcement learning (DRL) for robotics, sequential trajectory generation for multiprocess robotic tasks based on DRL is yet to be explored. In this article, the multiprocess task is formulated as a Markov decision process, and a nested dual-memory deep deterministic policy gradient algorithm with dynamic criteria is proposed, to generalize the traditional trajectory planning with predefined target point into a trajectory exploration problem aiming at a target area without solving inverse kinematics. First, a dual-memory architecture with local-to-global strategy is introduced to enhance the performance. Second, a novel nested architecture is proposed to generate sequential trajectory segments successively and asynchronously for the multiprocess task. Third, a compound reward system is designed and a weight coefficient matrix is adopted to balance the position control and the orientation control based on Tait–Bryan angles. In addition, a virtual twin system is established to promote the training efficiency, where the trajectory generated in simulation can be directly applied to the real physical platform. Finally, experimental results on both simulated and real-world applications have verified the performance of the proposed approach.

Distributionally robust frequency dynamic constrained unit commitment considering uncertain demand-side resources

Demand-side resources (DSR) have been considered as flexible frequency reserve providers in power systems. Given their uncertain nature in the reserve deployment and the load recovery periods, it is necessary to consider these uncertainties in the frequency dynamic constrained unit commitment (FDUC) model. This paper proposes a two-stage distributionally robust FDUC model to minimize the worst-case cost expectation under a set of probability distributions of DSR uncertainties, which are restricted by the supports and moments generated from statistical information. In addition, the cumulative frequency deviation during the entire regulation period is exploited as a frequency dynamic criterion. Particularly, it can quantify the regulation efficacy of the reserve resources with diverse frequency response characteristics, such as the dead-band time and the reserve delivery time. Simulations based on the IEEE 118-bus and 300-bus systems validate the effectiveness of the proposed method in hedging against the DSR uncertainties.

Mechanical properties and constitutive model of coral aggregate concrete subjected to dynamic uniaxial and triaxial compression

AbstractThe dynamic compressive mechanical performance of coral aggregate concrete (CAC) has been studied by the servo‐controlled true triaxial testing machine (TAWZ‐5000/3000), the failure modes and the stress–strain curves were obtained under various loading conditions. The effect of strain rates and the constant lateral pressure on the strength, deformation capacity, and failure modes of CAC were analyzed according to the results obtained from the test. The results show that the lateral pressure significantly changes the failure mode while the strain rate only affects the degree. The strength and deformation capacity will improve with the increase of strain rate and lateral pressure, and the lateral pressure diminishes the strain rate effect on mechanical properties. A 5‐parameter empirical dynamic failure criterion was established based on the William‐Warnke criterion. Finally, a 2‐stage dynamic multiaxial compressive constitutive model obeying the Weibull and Lognormal statistical distributions was established, and the model had well‐fitting results with the experimental results.

A Sampling-Based Algorithm with the Metropolis Acceptance Criterion for Robot Motion Planning

Motion planning is one of the important research topics of robotics. As an improvement of Rapidly exploring Random Tree (RRT), the RRT* motion planning algorithm is widely used because of its asymptotic optimality. However, the running time of RRT* increases rapidly with the number of potential path vertices, resulting in slow convergence or even an inability to converge, which seriously reduces the performance and practical value of RRT*. To solve this issue, this paper proposes a two-phase motion planning algorithm named Metropolis RRT* (M-RRT*) based on the Metropolis acceptance criterion. First, to efficiently obtain the initial path and start the optimal path search phase earlier, an asymptotic vertex acceptance criterion is defined in the initial path estimation phase of M-RRT*. Second, to improve the convergence rate of the algorithm, a nonlinear dynamic vertex acceptance criterion is defined in the optimal path search phase, which preferentially accepts vertices that may improve the current path. The effectiveness of M-RRT* is verified by comparing it with existing algorithms through the simulation results in three test environments.

An enhanced implicit viscosity ISPH method for simulating free-surface flow coupled with solid-liquid phase change

Free-surface flow coupled with solid-liquid phase change can be observed in many industrial applications, and it has a great influence on many industrial processes. In this paper, the Incompressible Smoothed Particle Hydrodynamics (ISPH) method is extended with solid-liquid phase change model. A novel implicit viscosity solver is adopted in which the implicit viscosity solver is moved behind the calculation of pressure force to eliminate the time step limitation and the numerical creeping of high viscosity. To reduce the compression caused by the delayed incompressibility correction, accurate wall boundary conditions are applied and an enhanced implicit viscosity Laplacian operator is proposed. Besides, a dynamic solid boundary criterion is proposed to deal with the changing solid-liquid interface. In addition, the enthalpy-based heat transfer model and the mushy zone viscosity model are introduced. The inter-particle conductivity between liquid and solid is adopted to consider the large contact thermal resistance between fluid and solid. As will be shown, our ISPH method is verified in its performance in simulating free-surface flow coupled with solid-liquid phase change by four numerical examples and has good advantages in simulation quality over the existing implicit viscosity algorithm, which, hopefully, is to provide applications in engineering.

Surgical Extent for Oral Cancer: Emphasis on a Cut-Off Value for the Resection Margin Status: A Narrative Literature Review.

The optimal cut-off point of the resection margin was recently debated in oral cancer. To evaluate the current evidence of the dynamic criteria of the resection margin, a review of the available literature was performed. Studies were sourced from PubMed and EMBASE by searching for the keywords "mouth neoplasm", "oral cancer", "oral cavity cancer", "oral squamous cell carcinoma", "tongue cancer", "margins of excision", "surgical margin" and "resection margin". We found approximately 998 articles on PubMed and 2227 articles on EMBASE. A total of 3225 articles was identified, and 2763 of those were left after removing the duplicates. By applying advanced filters about the relevance of the subjects, these were narrowed down to 111 articles. After the final exclusion, 42 full-text articles were reviewed. The universal cut-off criteria of 5 mm used for determining the resection margin status has been debated due to recent studies evaluating the impact of different margin criteria on patient prognosis. Of note, the degree of the microscopic extension from the gross tumor border correlates with tumor dimensions. Therefore, a relatively narrow safety margin can be justified in early-stage oral cancer without the additional risk of recurrence, while a wide safety margin might be required for advanced-stage oral cancer. This review suggests a surgical strategy to adjust the criteria for risk grouping and adjuvant treatments, according to individual tumor dimensions or characteristics. In the future, it might be possible to establish individual tumor-specific surgical margins and risk stratification during or after surgery. However, the results should be interpreted with caution because there is no strong evidence (e.g., prospective randomized controlled studies) yet to support the conclusions. Our study is meaningful in suggesting future research directions and discussions.

Admissible HVDC infeed capacity evaluation of receiving-end power grids

To fulfil the cross-regional bulk power delivery of renewable energy and alleviate the power shortage pressure of load centers, a number of line-commutated converter-based high voltage direct current (LCC-HVDC) transmission projects have been deployed in worldwide. Due to the system-wide operating risk sharply escalated with the intensively infeed of multiple large-capacity HVDC links, a vital knowledge gap exists in understanding the maximal admissible HVDC infeed capacity (AHIC) of receiving-end power grids. To tackle this issue, this paper proposes a novel AHIC evaluation method, which determines the maximal allowed total number and capacity of HVDC links that the receiving-end grid can accommodate while taking into account multi-preconceived fault security requirements. An improved dynamic system strength criterion is developed to assessing the immunity of post-contingency HVDC commutation failures (CF), which creatively considers the support effect from all AC buses based on the voltage sensitivity. The original two-stage model is decomposed into a construction master problem and an operation optimization subproblem, and then being iteratively solved using the generalized Benders decomposition algorithm. The effectiveness of the proposed approach is demonstrated on a modified IEEE RTS-79 system and a practical large-scale system.

Dynamical Disruption Timescales and Chaotic Behavior of Hierarchical Triple Systems

We examine the stability of hierarchical triple systems using direct N-body simulations without adopting a secular perturbation assumption. We estimate their disruption timescales in addition to the mere stable/unstable criterion, with particular attention to the mutual inclination between the inner and outer orbits. First, we improve the fit to the dynamical stability criterion by Mardling & Aarseth widely adopted in the previous literature. Especially, we find that that the stability boundary is very sensitive to the mutual inclination; coplanar retrograde triples and orthogonal triples are much more stable and unstable, respectively, than coplanar prograde triples. Next, we estimate the disruption timescales of triples satisfying the stability condition up to 109 times the inner orbital period. The timescales follow the scaling predicted by Mushkin & Katz, especially at high e out where their random walk model is most valid. We obtain an improved empirical fit to the disruption timescales, which indicates that the coplanar retrograde triples are significantly more stable than the previous prediction. We furthermore find that the dependence on the mutual inclination can be explained by the energy transfer model based on a parabolic encounter approximation. We also show that the disruption timescales of triples are highly sensitive to tiny changes of the initial parameters, reflecting the genuine chaotic nature of the dynamics of those systems.