Discontinuous Model Research Articles

Differential Sensitivity in Discontinuous Models

Differential Sensitivity in Discontinuous Models

Numerical simulation scheme of jointed rock masses using UAV photogrammetry and a disk-based discontinuous deformation analysis model

<abstract><p>The use of unmanned aerial vehicles (UAVs) for photogrammetry allows the rapid acquisition of high-resolution images of geological masses in complex landforms. However, effective analysis of the acquired image information remains a key research issue. At K158 + 837 on the Chongqing-Huaihua Railway, Baima jointed rock masses were reconstructed with high accuracy using UAV close-range photogrammetry technology, and rock discontinuities were extracted from the projected image. The proposed modeling algorithm for jointed rock masses enables the preprocessing of two-dimensional jointed rock mass slopes. Numerical simulations using the disk-based discontinuous deformation analysis method show that the discontinuity network formed by initial cutting significantly affects the subsequent crack development. Meanwhile, simulation results under different scenarios indicate the importance of the pre-reinforcement measures applied to unstable rock masses. The workflow developed based on these results can serve as a reference for the comprehensive acquisition, recognition and numerical modeling analysis of similar jointed rock masses.</p></abstract>

Oxidation-induced recrystallization and damage mechanism of a Ni-based single-crystal superalloy during creep

The creep tests for Ni-based single-crystal superalloy are carried out under 980 °C, and the microstructure at the crack tip is characterized at micro- and nano- scales. Numerous γ’ phase dissolution, nucleation and growth of fine grains are observed near the crack. In addition, γ’ phase did not effectively hinder the nucleation and growth of recrystallization grains at the oxidation-affected zone. Instead, recrystallization promoted the degradation of the γ’ phase to dissolve along the recrystallized grain boundaries. Combining the sub-grain boundary growth model proposed by Winning et al. and the discontinuous recrystallization model suggested by D.G. Cram, a recrystallization and oxidative damage model for Ni-based single-crystal superalloy is proposed. • Local polycrystallization or recrystallization will greatly damage the high-temperature properties of the alloy. From the point of view of Ni-based single-crystal superalloy design, polycrystallization during medium-high temperature creep is very rare and should be strictly avoided. • Many researches have paid attention to the recrystallization of polycrystalline Ni-based superalloys. However, there is no report about the appearance of polycrystallization region in Ni-based single crystal superalloys during creep. Additionally, systematic research and explanation on the mechanism of discontinuous recrystallization of Ni-based SC superalloy are also very lacking. • In this paper, it is found for the first time that in the process of medium-high temperature (980 °C) creep under low stress level, polycrystallization region and a large amount of γ’ phase dissolve appeared at the crack tip, which leads to a sharp decline in the properties of the alloy. Researchers believed that the γ’ phase is the main factor that hinder the recrystallization of Ni-based single-crystal alloy. Nevertheless, this paper propose that the local strain and depletion of solute atoms makes the sub-grain boundaries tend to become the nucleation of recrystallization.

TOE: A Grid-Tagging Discontinuous NER Model Enhanced by Embedding Tag/Word Relations and More Fine-Grained Tags

So far, discontinuous named entity recognition (NER) has received increasing research attention and many related methods have surged such as hypergraph-based methods, span-based methods, and sequence-to-sequence (Seq2Seq) methods, etc. However, these methods more or less suffer from some problems such as decoding ambiguity and efficiency, which limit their performance. Recently, grid-tagging methods, which benefit from the flexible design of tagging systems and model architectures, have shown superiority to adapt for various information extraction tasks. In this paper, we follow the line of such methods and propose a competitive grid-tagging model for discontinuous NER. We call our model TOE because we incorporate two kinds of Tag-Oriented Enhancement mechanisms into a state-of-the-art (SOTA) grid-tagging model that casts the NER problem into word-word relationship prediction. First, we design a Tag Representation Embedding Module (TREM) to force our model to consider not only word-word relationships but also word-tag and tag-tag relationships. Concretely, we construct tag representations and embed them into TREM, so that TREM can treat tag and word representations as queries/keys/values and utilize self-attention to model their relationships. On the other hand, motivated by the Next-Neighboring-Word (NNW) and Tail-Head-Word (THW) tags in the SOTA model, we add two new symmetric tags, namely Previous-Neighboring-Word (PNW) and Head-Tail-Word (HTW), to model more fine-grained word-word relationships and alleviate error propagation from tag prediction. In the experiments of three benchmark datasets, namely CADEC, ShARe13 and ShARe14, our TOE model pushes the SOTA results by about 0.83%, 0.05% and 0.66% in F1, demonstrating its effectiveness.

Brownian Motion: A Financial Contradiction and Discontinuous Continuity Modeling

Brownian Motion: A Financial Contradiction and Discontinuous Continuity Modeling

In-plane seismic performance of an innovative steel modular reinforcement system for URM walls

An experimental and numerical research, aimed at evaluating the in-plane seismic performance of an innovative steel modular system for the reinforcement of load-bearing masonry walls (named "Resisto 5.9", designed by Progetto Sisma s.r.l.), is currently underway at the EUCENTRE Foundation in Pavia. Two different masonry typologies, representing common solutions in Italian existing buildings, were considered in this campaign: one made up with solid clay bricks and lime mortar, with "header bond" pattern, and the other with a typical Italian hollow clay "doppio UNI" unit and cement-lime mortar, assembled in a "Flemish bond" pattern. The experimental tests included first the complete mechanical characterization of units, mortars, masonry typologies and of the strengthening system components (i.e. steel elements and anchors). In-plane quasi-static tests were performed on different batches of full--scale specimens to investigate the influence of the proposed reinforcement system on the lateral in-plane response of the walls, compared to their unreinforced conditions. The cyclic behaviour of the masonry piers was analysed in terms of elastic stiffness, lateral strength, displacement capacity and energy dissipation, depending on the achieved damage mechanism. The numerical study of the ongoing campaign consisted of a series of parametric analyses on advanced discontinuous models based on the Distinct Element Method (DEM), considering different wall dimensions, vertical load levels and boundary conditions, in addition to those tested experimentally. Moreover, the numerical campaign was extended also to other possible masonry typologies, varying the bond pattern and the mechanical properties with respect to the experimentally tested solutions. In this paper, the results of the experimental tests on solid brick masonry together with a preliminary overview of the findings of the numerical study, still ongoing, were reported.

Estimation of Causal Effect of treatment via Fuzzy Regression Discontinuity Designs

In some cases, researchers need to know the causal effect of the treatment in order to know the extent of the effect of the treatment on the sample in order to continue to give the treatment or stop the treatment because it is of no use. The local weighted least squares method was used to estimate the parameters of the fuzzy regression discontinuous model, and the local polynomial method was used to estimate the bandwidth. Data were generated with sample sizes (75,100,125,150 ) in repetition 1000. An experiment was conducted at the Innovation Institute for remedial lessons in 2021 for 72 students participating in the institute and data collection. Those who used the treatment had an increase in their score after treatment by 25.95%. 
 
 
 Paper type This Research is extracted from a master's thesis on statistics entitled “Estimation of Fuzzy Regression Discontinuity model with the application"

Digital servitization: An effective tool of attracting customers in modern business world

Digital technology is present within each stage of process and are present at all the stages as well. There are two types of models in digital servitization. These two are continuous and discontinuous processes. The continuous model helps to develop the existing business model of the company and enhances it for better understanding. Discontinuous model makes a whole new business model for the company and scraps out the old model. The company has to change its whole business model when they adopt discontinuous model for itself. This model is more time consuming and more costly than the other.

Continuous–Discontinuous Element Numerical Modeling of Damage and Fracture Characteristics of a Loaded Coal

Continuous–Discontinuous Element Numerical Modeling of Damage and Fracture Characteristics of a Loaded Coal

Contact Overlap Calculation Algorithms and Benchmarks Based on Blocky Discrete-Element Method

The mechanical response of granular materials has been investigated widely using discontinuous modeling, such as the discrete-element method (DEM). Contact detection and contact resolution have been critical issues when modeling multiple body contacts, especially for arbitrary polyhedral blocks. In this study, the contact overlap calculation algorithms, including polyhedron–polyhedron and polyhedron–boundary contact, were developed to calculate the contact characteristics. For polyhedron–polyhedron contact, the contact overlap volume algorithm is developed based on the geometric dualization theory. The Gilbert–Johnson–Keerthi (GJK) and Quickhull algorithms are used to calculate the overlap polyhedron. The contact characteristics, such as normal direction (n), contact area (a), and penetration depth (un) could be extracted from the contact overlap volume. For polyhedron–boundary contact, a novel and effective algorithm is presented, where the polyhedron–boundary contact is transformed into polyhedron–triangle contact. Then, two types of benchmarks are used to verify the previously mentioned algorithms, which demonstrated that the algorithms could handle the complicated contact types and maintained contact continuity even from face to edge contact. As a complex benchmark, the failure process in a masonry structure is simulated and compared with the model test.

Does the employment effect of national minimum wage vary by non‐employment rate? A regression discontinuity approach

AbstractWe extend the Regression Discontinuity model to evaluate the procyclicality of employment effect of minimum wage and show that previous estimates may be biased due to failure to account for the local non‐employment rate. The results suggest that the positive employment effect of increasing minimum wage is strongly procyclical, that is, is more pronounced in areas with low non‐employment rates. Under an assumption that employers have no direct impact around the cut‐off point, the results suggest that a higher minimum wage increases labour supply of young workers.

Impact of prey refuge in a discontinuous Leslie-Gower model with harvesting and alternative food for predators and linear functional response

Since in nature there are species that take refuge, totally or proportionally, from the predator if the prey population size exceeds a threshold value, and become available again to the predator, with linear predator functional response, if its population size is higher than the threshold value, in this work we show all the changes in the dynamics presented by two discontinuous Leslie–Gower predator–prey models, assuming harvesting and alternative food for predators and total protection, or a constant proportional refuge of prey from being consumed by the predator when its population size is below the threshold value. The conditions on their parameters to determine the dynamics of each discontinuous model are developed by means of a bifurcation analysis, with respect to the threshold value of the prey population size and the collection rate for predators. It is concluded that for certain conditions on their parameters, the prey population size could reach a convergence equal or higher than its threshold value when considering the discontinuous model with a mechanism to protect prey from being consumed by the predator, as opposed to the discontinuous model with a constant proportion of prey refuges above the threshold value, whose convergence could be lower, equal or higher than the threshold value.

The Effect of School District Consolidation on Student Achievement: Evidence From Arkansas

School district consolidation is one of the most widespread education reforms of the last century, but surprisingly little research has directly investigated its effectiveness. To examine the impact of consolidation on student achievement, this study takes advantage of a policy that requires the consolidation of all Arkansas school districts with enrollment of fewer than 350 students for two consecutive school years. Using a regression discontinuity model, we find that consolidation has either null or small positive impacts on student achievement in math and English Language Arts (ELA). We do not find evidence that consolidation in Arkansas results in positive economies of scale, either by reducing overall cost or by allowing for a greater share of resources to be spent in the classroom.

The Impact of the Workforce Innovation and Opportunity Act on Agency-Level Vocational Rehabilitation Outcomes for Adults and Youth With Blindness and Low Vision

The purpose of this study was to evaluate the impact of the U.S. Workforce Innovation and Opportunity Act (WIOA) on outcomes (competitive employment rates and median earnings) for adult and youth vocational rehabilitation consumers with blindness or low vision (B/LV) and to determine whether impacts differed by agency type. We utilized RSA-911 data to create two agency-level longitudinal datasets, one for youth and one for adults, with 6-year pre-WIOA and 3-year post-WIOA periods. Data were analyzed using discontinuous growth modeling to assess longitudinal changes in agency-level outcomes through the inclusion of variables representing WIOA and subsequent change in response to WIOA. After WIOA, both youth and adult agency-level competitive employment rates decreased significantly for consumers with B/LV, with a larger impact on youth, and median earnings increased. Results document that the impact of WIOA on agencies varied widely. Separate agencies had a significant decrease in adult competitive employment rates for consumers with B/LV and a significant increase in median earnings compared with combined agencies. Overall, the influence of WIOA on B/LV consumer outcomes appears to be mixed at best, and the effect is surprisingly similar for youth and adults.

Electronic nicotine delivery systems (ENDS) dependence among Texas Young Adults, 2014-2019: Increasing trajectory after the 2017 surge in vape pod popularity

IntroductionUse of electronic nicotine delivery systems (ENDS) increased significantly after 2017. The increase is attributed to a surge in popularity of vape pods containing nicotine salts, which are high nicotine concentration ENDS that may heighten risk for dependence. However, little is known about changes in ENDS dependence before and after the 2017 surge. We examined the trajectory of ENDS dependence among young adults from 2014 to 2019. MethodsParticipants were 1700 18–25-year-olds (57.6 % female) from 24 Texas colleges who reported past 30-day ENDS use in at least one of eight study waves. ENDS dependence was assessed at all waves with one item, use of ENDS within 30 min of waking. A discontinuous growth curve model was fit to test the hypothesis that the ENDS dependence trajectory would increase only after 2017, from 2018 to 2019. The model included socio-demographic and cigarette dependence covariates ResultsThe proportion of young adults reporting ENDS dependence ranged from 2.3 % in 2014 to 8.2 % in 2019. Results from the discontinuous growth curve model indicated that the ENDS dependence trajectory was flat from fall 2014 to spring 2017. However, the post-2017 trajectory, from spring 2018 to spring 2019, was positive and significant indicating that the proportion of young adults reporting ENDS dependence increased after 2017. ConclusionsThe increase in ENDS dependence after 2017 likely resulted from the surge in popularity of vape pods containing nicotine salts. These vape pods are a disruptive technology that may result in more young adults developing nicotine dependence symptoms than do earlier generation devices.

Frequency entrainment and suppression of stick–slip vibrations in a 3 DoF discontinuous disc brake model

Friction-induced stick–slip vibration has been identified as the main reason for various types of disc brake noises like creep groan, squeak and creak. In this work, we investigate the suppression of stick–slip vibrations in disc brakes due to the application of a small-amplitude normal harmonic force on the brake pad. The discontinuity induced bifurcations that lead to such suppression are studied in detail. The frequency range of the normal force in which suppression of stick–slip vibration occur is identified. A 3 DoF discontinuous model of the disc brake is considered. The discontinuous oscillator is modelled as a Filippov system with smooth vector fields separated by a discontinuity surface. It is shown that the normal harmonic force entrains the non-smooth limit cycle even for very small forcing amplitudes. Different frequency intervals exhibiting harmonic, super-harmonic, and sub-harmonic entrainments are identified. It is demonstrated that the initiation and termination of these entrainment intervals are associated with Neimark–Sacker bifurcations. It is also shown that discontinuity induced grazing-sliding mechanism brings about these bifurcations. Switching-sliding bifurcations happening in the entrainment region give rise to a sub-interval which is associated with suppression of stick–slip vibrations. We also report interesting discontinuity induced bifurcation scenarios in higher order entrainment regimes like grazing-sliding involving different orbit loops at lower and upper limits of the interval and splitting–merging of the sliding surface. • Stick–slip vibration suppression in disc brakes by using normal force is studied. • Various entrainment regions are detected and studied by Filippov’s method. • Discontinuity induced bifurcations causing these entrainments are analysed. • Entrainment sub-intervals with suppressed stick–slip vibration are identified.

Cue-induced cocaine craving enhances psychosocial stress and vice versa in chronic cocaine users

Stress and craving, it has been found, contribute to the development and maintenance of and relapse in cocaine use disorder. Chronic cocaine users (CU), previous research has shown, display altered physiological responses to psychosocial stress and increased vegetative responding to substance-related cues. However, how psychosocial stress and cue-induced craving interact in relation to the CU’s physiological responses remains largely unknown. We thus investigated the interaction between acute psychosocial stress and cocaine-cue-related reactivity in 47 CU and 38 controls. In a crossed and balanced design, the participants were randomly exposed to a video-based cocaine-cue paradigm and the Trier Social Stress Test (TSST) or vice versa to investigate possible mutually augmenting effects of both stressors on physiological stress responses. Over the course of the experimental procedure, plasma cortisol, ACTH, noradrenaline, subjective stress, and craving were assessed repeatedly. To estimate the responses during the cocaine-cue paradigm and TSST, growth models and discontinuous growth models were used. Overall, though both groups did not differ in their endocrinological responses to the TSST, CU displayed lower ACTH levels at baseline. The TSST did not elevate craving in CU, but when the cocaine-cue video was shown first, CU displayed an enhanced cortisol response to the subsequent TSST. In CU, cocaine-cues robustly evoked craving but no physiological stress response, while cue-induced craving was intensified after the TSST. Taken together, though CU did not show an altered acute stress response during the TSST, stress and craving together seemed to have mutually augmenting effects on their stress response.

Exploring the Effects of Traffic Noise on Innovation through Health Mechanism: A Quasi-Experimental Study in China

Noise pollution poses a significant hazard to humans by disrupting the maintenance of the quiet environment that is thought to promote innovation. In this study, the causal relationship between traffic noise and innovation was explored using four models. First, the panel data model with fixed effects was applied to determine the impact of traffic noise on innovation. Second, the interaction model was used to estimate the health regulatory effect. Third, the regression discontinuity model was used to identify the natural experience of the impact of traffic noise on innovation and further determine the causal effect of the noise threshold. Finally, the difference-in-differences model was used to identify the micro impact of traffic noise on innovation. The results show that from macro and micro perspectives, traffic noise suppresses innovation, and that health has a differential impact on the traffic noise–innovation relationship. In addition, we identified the critical point at which the impact of traffic noise on innovation is favorable owing to the white noise effect, providing a quantitative basis for policy implementation. Our results show that current environmental noise regulations must be re-examined to determine new measures for improving the innovative acoustic environment, promoting innovation, and achieving sustainable economic development.

The impact of an unemployment insurance reform on incidence rates of hospitalisation due to alcohol-related disorders: a quasi-experimental study of heterogeneous effects across ethnic background, educational level, employment status, and sex in Sweden

BackgroundMany Western countries have scaled back social and health expenditure, including decreases in the generosity and coverage of unemployment insurance, resulting in negative effects on general health and well-being at the aggregate level. Yet, research has not sufficiently looked into heterogeneity of such effects across different subgroups of the population. In Sweden, the 2006 unemployment insurance reform, implemented on the 1st of January 2007, encompassed a drastic increase of insurance fund membership fees, reduced benefit levels, and stricter eligibility requirements. As this particularly affected already socioeconomically disadvantaged groups in society, such as foreign-born and low-educated individuals, the current study hypothesise that the reform would also have a greater impact on health outcomes in these groups.MethodsBased on register data for the total population, we utilise a quasi-experimental approach to investigate heterogeneous health effects of the reform across ethnic background, educational level, employment status, and sex. Due to behaviourally caused diseases having a relatively shorter lag time from exposure, hospitalisation due to alcohol-related disorders serves as the health outcome. A series of regression discontinuity models are used to analyse monthly incidence rates of hospitalisation due to alcohol-related disorders among individuals aged 30–60 during the study period (2001–2012), with the threshold set to the 1st of January 2007.ResultsThe results suggest that, in general, there was no adverse effect of the reform on incidence rates of hospitalisation due to alcohol-related disorders. A significant increase is nonetheless detected among the unemployed, largely driven by Swedish-born individuals with Swedish-born or foreign-born parents, low-educated individuals, and men.ConclusionsWe conclude that the Swedish 2006 unemployment insurance reform generally resulted in increasing incidence rates of hospitalisation due to alcohol-related disorders among unemployed population subgroups known to have higher levels of alcohol consumption.

Numerical analysis of the hydraulic fracture communication modes in fracture-cavity reservoirs

The fracture-cavity carbonate reservoirs in the Tahe Oilfield in China are mainly exploited by fracturing. We need the hydraulic fractures to communicate with caves to create a flow channel. However, due to the existence of the fracture-cavity systems, the hydraulic fracture propagation morphology is complicated, while the propagation characteristics are not clear. To analyze the hydraulic fracture propagation in fracture-cavity carbonate formations, based on the discontinuous discrete fracture model, we developed a solid-seepage-freeflow coupled fracturing model for fracture-cavity formations, which can simulate the complex interaction behavior of fractures and caves. Based on the simulation results, we found the interaction rule between hydraulic fractures and fracture-cavity systems: the stress concentration around caves is the main factor that determines the fracture propagation path. Deflection due to stress concentration is usually not conducive to communication, while natural fractures distributed around caves could break the rejection action. Increasing the hydraulic energy in the hydraulic fracture can make fracture propagate directly and reduce the influence of deflection. The steering fracture formed by temporary plugging is beneficial to the communication of fracture-cavity systems in the non-principal stress direction. According to the simulation results of different fracture-cavity characteristics, we raised four optimization communication modes for fracture-cavity carbonate formation to provide references for fracturing optimization design and parameter optimization.