Train Track Research Articles

Prevalence of self-reported lower limb overuse problems in highly trained track and field athletes during 12 weeks of pre-season training

Prevalence of self-reported lower limb overuse problems in highly trained track and field athletes during 12 weeks of pre-season training

Modeling and Tuning of Electronic Throttle Control System in Formula Student Car

The Lookprabida formula student team uses an electronic throttle control (ETC) system in the racecar. Unfortunately, the ETC system cannot regulate the throttle valve to closely pursue angular setpoints. Thus, this paper endeavors to improve the response of the ETC system in racing cars. The ETC system is first examined using frequency response analysis. Parameter identification is carried out to obtain a mathematical model for the electronic throttle body. The Ziegler-Nichols’ second method is then applied to preliminarily select the proportional integral derivative (PID) gains using MATLAB/Simulink®. Then, the ETC system fine-tuning on the experimental set is carried out. The final PID controller design results in a reduction in the settling time from 0.35 to 0.20 s, overshoot from 29.6 to 19.33%, and steady-state error from 2.00 to 0.22%. The racecar with the finally designed PID gains is tested on a training track; the root mean square error (RMSE) shows that the throttle valve approaches much closer to angular setpoints.

Testing and modelling of transient adhesion phenomena in rolling-sliding contacts

Transient adhesion effects in rolling–sliding contacts influence all aspects of train–track interaction. This is of high importance specifically when these effects result in critically low adhesion, which poses a risk to traction and braking of railway vehicles. This study presents a model that can replicate the transient changes of the coefficient of adhesion with tested water and solid particle mix. The experimental data for the model are measured using a commercial ball-on-disc tribometer. The experimental results showed a liquid reservoir in front of the contact area that slowly reduces in size. This observation was used in the modelling approach to divide the calculation into two stages where the reservoir is present and when it disappears. The model was able to reproduce the occurrence of low adhesion region seen in experimental results with different particle concentrations.

Biatrial myopathy in heart failure with preserved ejection fraction.

Left atrial (LA) myopathy is increasingly recognized as an important phenotypic trait in heart failure (HF) with preserved ejection fraction (HFpEF). Right atrial (RA) remodelling and dysfunction also develop in HFpEF, but little data are available regarding the clinical characteristics and pathophysiology among patients with isolated LA, RA, or biatrial myopathy. Patients with HFpEF underwent invasive haemodynamic exercise testing, comprehensive imaging including speckle tracking strain echocardiography, and clinical follow-up at Mayo Clinic between 2006 and 2018. LA myopathy was defined as LA volume index >34 ml/m2 and/or LA reservoir strain ≤24% and RA myopathy by RA volume index >39 ml/m2 in men and >33 ml/m2 in women and/or RA reservoir strain ≤19.8%. Of 476 consecutively evaluated patients with HFpEF defined by invasive exercise testing with evaluable atrial structure/function, 125 (26%) had no atrial myopathy, 147 (31%) had isolated LA myopathy, 184 (39%) had biatrial myopathy, and 20 (4%) had isolated RA myopathy. Patients with HFpEF and biatrial myopathy had more atrial fibrillation, poorer left ventricular systolic and diastolic function, more severe pulmonary vascular disease, tricuspid regurgitation, ventricular interdependence and right ventricular dysfunction, and poorer cardiac output reserve with exercise. There were 94 patients with events over a median follow-up of 2.9 (interquartile range 1.4-4.6) years. Individuals with biatrial myopathy had an 84% higher risk of HF hospitalization or death as compared to those with isolated LA myopathy (hazard ratio 1.84; 95% confidence interval 1.16-2.92, p = 0.01). Biatrial myopathy identifies patients with more advanced HFpEF characterized by more severe pulmonary vascular disease, right HF, poorer cardiac reserve, and a greater risk for adverse outcomes. Further study is required to define optimal strategies to treat and prevent biatrial myopathy in HFpEF.

Frequency Spectra Analysis of Vertical Stress in Ballasted Track Foundations: Influence of Train Configuration and Subgrade Depth

Railway tracks experience stress during train passage. Understanding these subgrade stresses is essential for the design of track foundations and assessing their serviceability. However, few studies have explored the theoretical aspects of stress response in relation to train configuration. Therefore, this paper introduces a subgrade stress model for ballasted tracks, aiming to analyze the stress fields in track foundations under train loading. The model employs a unit impulse approach to represent the periodic axle sequence of a train moving at constant speed. It characterizes vertical stress transmission within geotechnical media using stochastic diffusion theory. With train configuration, track structure, and soil properties as inputs, the model can reconstruct the quasi-static time history and frequency spectrum of vertical subgrade stress at various depths. Frequency analysis indicates that as the number of axles increases, the dominant stress frequencies first align with integer multiples of the “bogie-passage frequency” and subsequently with integer multiples of the “vehicle-passage frequency.” Zero magnitudes may appear at dominant frequencies, depending on a vehicle's length and wheelbase. Peak stress magnitudes rapidly diminish at higher frequencies, with this attenuation becoming more pronounced as subgrade depth increases. The proposed model accounts for the structural features of trains and tracks, as well as the material properties of subgrade fills. It elucidates the mechanisms driving the quasi-static response of the subgrade when subjected to passing trains.

A Novel Approach for Train Tracking in Virtual Coupling Based on Soft Actor-Critic

The development of virtual coupling technology provides solutions to the challenges faced by urban rail transit systems. Train tracking control is a crucial component in the operation of virtual coupling, which plays a pivotal role in ensuring the safe and efficient movement of trains within the train and along the rail network. In order to ensure the high efficiency and safety of train tracking control in virtual coupling, this paper proposes an optimization algorithm based on Soft Actor-Critic for train tracking control in virtual coupling. Firstly, we construct the train tracking model under the reinforcement learning architecture using the operation states of the train, Proportional Integral Derivative (PID) controller output, and train tracking spacing and speed difference as elements of reinforcement learning. The train tracking control reward function is designed. Then, the Soft Actor-Critic (SAC) algorithm is used to train the virtual coupling train tracking reinforcement learning model. Finally, we took the Deep Deterministic Policy Gradient as the comparison algorithm to verify the superiority of the algorithm proposed in this paper.

A pilot study evaluating the preventive effects of platform-end lengthwise fencing on trespassing, person struck by train and traffic delays

Background: Trespassing at train tracks and “person under train” (PUT) incidents are serious health, societal and transportation concerns. There is a need for developing different measures to prevent these events. Here, we hypothesized that platform-end lengthwise fences (PLF) reduce trespassing, the number of PUT incidents (suicides and accidents), and train traffic delays. Method: PLFs were installed as the intervention at one station in Stockholm in 2020. The number of trespassers detected using CCTV-cameras was compared before and after at the intervention station over a total period of 29 months (using incidence rate ratio, IRR). The reduction in the number of PUT (over 20 years) and train traffic delays (over 9 years) was also investigated by IRR, and by using three control groups. Results: After installation of PLF there was a significant ∼90% reduction in trespasses (IRR = 0.10, 95%CI 0.04–0.23; one-sided exact p < 0.0001). No PUT incident occurred at the intervention station after the installation, compared to 1.11 per year before installation (IRR = 0.32, 95%CI 0–1.82; one-sided exact p = 0.1216). There was a significant reduction in delay minutes post installation compared to before the installation (Mann Whitney U = 0, upper one-sided exact p = 0.0357). The effect of the PLF was also observable in comparison to the three control groups, suggesting that the preventive effect was not due to wider societal events affecting all stations. Conclusion: PLF had a large effect on reducing the number of trespasses and the number of delay minutes due to trespasses and PUT incidents. PLF may also have an effect of reducing PUT incidents. Practical Applications: PLF is deemed to be relatively easy and cheap to install and thus scalable (as compared to full barriers, e.g., platform screen doors) and may be considered at platform-ends having an exit, provided there is enough space to install them.

A dual-kinetic energy harvester operating on the track and wheel of rail deceleration system for self-powered sensors

Alternative energy sources play a crucial role in Outback rail systems, where electrical infrastructure is unavailable for automated power devices used for traffic lights, surveillance cameras, sensors, and other safety equipment at railway stations and intersections. The current study proposes an innovative dual-kinetic energy harvester design to reduce train speed at intersections and before it comes to a halt at the station. Additionally, it harvests energy from both the train track and wheel simultaneously. The proposed device consists of three main units. The first unit utilizes vibrational movement based on a rack pinion. An efficient dual-kinetic energy harvesting system has been developed, utilizing a novel concept that captures the vibration energy generated by the movement of the rail under the influence of the train’s weight. Additionally, as the train passes at high speed, the train wheel’s energy will be transmitted to the top of the device, moving the rack to a depth of 30 mm. A spiral spring is employed to restore the rack to its initial position after the wheel has passed. The tension force of the spring causes the rack to adhere to the track, enabling the transmission of vibrations generated by the track’s movement and releasing energy, causing the motion to be induced during the return stroke. The second component is the transmission unit. The bidirectional rotational motion from the rack pinion is converted into unidirectional rotational motion using three bevel gears, two roller clutches, and a planetary gearbox to enhance the rotations of the generator shaft. The third component is a 1500 W/180 V DC motor for electricity generation. Lastly, the charging circuit was developed to recharge supercharged capacitors. The proposed system was installed before the railway station, and practical tests were conducted, which showed an efficiency of up to 55%.

Dynamic Response of Transmission Tower-Line Systems Due to Ground Vibration Caused by High-Speed Trains

With the continuous expansion of the scale of power grid and transportation infrastructure construction, the number of crossovers between transmission lines and high-speed railways continues to increase. At present, there is a lack of systematic research on the dynamic characteristics of transmission tower-line structures crossing high-speed railways under vehicle-induced ground vibration. This article focuses on the phenomenon of accidents such as line drops when crossing areas in recent years and establishes a high-speed train track foundation soil finite element model in ABAQUS that considers track irregularity. The three-dimensional vibration characteristics and attenuation law of train ground vibration are analyzed. Acceleration data for key points are also extracted. A separate finite element model of the transmission tower-line system is established in ANSYS, where acceleration is applied as an excitation to the transmission tower-line system, and the coupling effect between the tower and the line is considered to analyze its dynamic response. Subsequently, modal analysis is conducted on the tower-line system, providing the vibration modes and natural frequencies of the transmission tower-line structure. The effects of factors such as train speed, soil quality, and distance from the tower to the track on the dynamic response of the transmission tower-line system under vehicle-induced ground vibration are studied. The results show that the speed range (300 km/h–400 km/h) and track distance range (4.5 m–30 m) with the greatest impacts are obtained. The research results can provide a reference for the reasonable design of transmission tower-line systems in high-speed railway sections.

Extreme-oriented sensitivity analysis using sparse polynomial chaos expansion. Application to train–track–bridge systems

The use of sensitivity analysis is essential in model development for the purposes of calibration, verification, factor prioritization, and mechanism reduction. While most contributions to sensitivity methods focus on the average model response, this paper proposes a new sensitivity method focusing on the extreme response and structural limit states, which combines an extreme-oriented sensitivity method with polynomial chaos expansion. This enables engineers to perform sensitivity analysis near given limit states and visualize the relevance of input factors to different design criteria and corresponding thresholds. The polynomial chaos expansion is used to approximate the model output and alleviate the computational cost in sensitivity analysis, which features sparsity and adaptivity to enhance efficiency. The accuracy and efficiency of the method are verified in a truss structure, which is then illustrated on a dynamic train–track–bridge system. The role of the input factors in response variability is clarified, which differs in terms of the design criteria chosen for sensitivity analysis. The method incorporates multi-scenarios and can thus be useful to support decision-making in design and management of engineering structures.

Taking the high-edge route of rank-3 outer space

Principal fully irreducible outer automorphisms were introduced in [Y. Algom-Kfir, I. Kapovich and C. Pfaff, Stable strata of geodesics in outer space, Int. Math. Res. Not. 2019(14) (2019) 4549–4578] to emulate principal pseudo-Anosov surface homeomorphisms, i.e. those whose attracting and repelling invariant foliations have only 3-pronged singularities. It is proved in [Y. Algom-Kfir, I. Kapovich and C. Pfaff, Stable strata of geodesics in outer space, Int. Math. Res. Not. 2019(14) (2019) 4549–4578] that these outer automorphisms semi-mimic principal pseudo-Anosov surface homeomorphisms in important ways. We prove here which rank-3 graphs carry train track representatives of principal fully irreducible outer automorphisms. As a corollary, one obtains which simplices of rank-3 Culler–Vogtmann outer space principal axes pass through.

Diastolic disfunction in systemic right ventricle: a cardiac magnetic resonance study on atrial function in congenital corrected transposition of great arteries patients

Abstract Background congenital corrected transposition of great arteries (ccTGA) leads to systemic position of the right ventricle (sRV). Patients with ccTGA are usually asymptomatic in the first decades of life but over time sRV will fail to support elevated systemic pressure, possibly leading to systolic heart failure (HF) in adulthood. Several factors have been associated with sRV failure and worse prognosis such as tricuspid valve dysfunction, conduction abnormalities, previous surgery due to associated lesions. However, little is known about diastolic function in sRV. We hypothesize that diastolic dysfunction characterizes sRV pathophysiology, therefore an accurate evaluation of diastolic function would allow a better assessment and risk stratification of patients. The present study aims to investigate the diastolic function in patients with ccTGA by assessing left atrial (LA) morpho-functional parameters. Methods we retrospectively examined Cardiac Magnetic Resonance (CMR) imaging of 33 ccTGA patients clinically referred to our Center between April 2014 and December 2022. ccTGA patients were matched based on sex and age with a healthy volunteer population (control group) and a group of patients with Hypertrophic Cardiomyopathy (HCM) diagnosed with HFpEF according to HF guidelines criteria. LA morpho-functional parameters were compared among the three groups: LA volumes (obtained by the length-area method), ejection fraction (EF) and, by means of feature tracking analysis, strain reservoir (εs), conduit (εe) and booster pump (εa). All patients were in sinus rhythm at the time of CMR. Results In comparison with the control group, ccTGA patients had a significant impairment in LA function (LA EF: 41,6 ± 15,1 vs 63,9 ± 7,8, p &amp;lt; 0,001, εs: 19,0 ± 8,3 vs 38,0 ± 10,3, p &amp;lt; 0,001, εe: 11,7 ± 5,9 vs 21,1 ± 8,3 p &amp;lt; 0,001, εa: 7,6 ± 4,1 vs 16,8 ± 6,1, p &amp;lt; 0,001). Conversely, no significant difference was found between ccTGA and HCM group regarding LA function (EF: 41,6 ± 15,1 vs 42,0 ± 10,1, εs: 19,0 ± 8,3 vs 22,6 ± 8,8, εe: 11,7 ± 5,9 vs 12,6 ± 7,0, εa: 7,6 ± 4,1 vs 10 ± 3,7). As for morphological parameters, ccTGA patients had an increase of LA volumes compared to both the control group and HCM patients. Conclusion ccTGA patients present an impaired LA function and a significative increase in LA volume consistent with the presence of diastolic disfunction. Further studies are needed to assess the clinical impact of morpho-functional LA impairment in ccTGA patients.

Left atrial appendage morphology and function predict thromboembolic risk in patients with embolic stroke of undetermined sources

Abstract Introduction Embolic stroke of undetermined sources (ESUS) is supposed to be associated with intracardiac thrombus formation, in particular in the left atrial appendage (LAA). We aimed to investigate the impact of LAA morphology and function on thromboembolic risk condition (TRC) and LAA thrombus in ESUS patients. Methods 185 ESUS patients (mean age 68 ±13 years, 33% female) without history of AF were included. All patients underwent clinical evaluation by CHA2DS2-VASc and complete transthoracic and transesophageal echocardiography shortly after index ESUS (4 days, IQR 3-6). LAA function and LAA morphology were evaluated by conventional 2D and 3D echocardiography and speckle tracking strain. TRC was defined as combination of thrombus, sludge and spontaneous echo contrast (SEC) in LAA. Results In 185 study patients, following LAA types were found: chicken wing (LAA CW) 79 (43%), windsock 64 (34%), cactus 35 (19%), cauliflower 7 (4%) and multilobate LAA, defined as LAA with ≥ 1 lobe, in 115 (62%) of patients. TRC was found in 123 (67%) and thrombus formation in 29 (16%). LAA CW and multilobate LAA were independent predictors of TRC (OR 2.3 (CI 1.2 - 4.5), p= 0. 01 and OR 2.2 (CI 1.2 - 4.2), p= 0.02, respectively) and furthermore, LAA CW and LAA-Sr were independent predictors of LAA thrombus (OR 2.5 (CI 1.1 - 5.8), p=0.04 and OR 0.9 (CI 0.8 – 1.0), p&amp;lt;0.01, respectively), all adjusted for CHA2DS2-VASc-score. Conclusion LAA type CW, multilobate LAA and novel LAA strain predicted independently TRC and LAA thrombus, respectively. These results indicate that LAA morphology and function are important in assessment of thromboembolic risk in ESUS patients.Table 1.

Dissociation of LA volume and deformation is a hallmark of ATTR-CA

Abstract Background Transthyretin Cardiac amyloidosis (ATTR-CA) is associated with an infiltrative left atrial (LA) cardiomyopathy. Purpose We sought to identify unique characteristics of LA cardiomyopathy in CA compared to non-amyloid states of left ventricular hypertrophy (LVH). Methods In suspected patients, a diagnosis of ATTR-CA was made by a positive Tc-99m PYP in conjunction with negative serum/urine studies for a clonal plasma cell dyscrasia. Endomyocardial biopsy was performed when clinically indicated. All patients underwent complete transthoracic echocardiography (TTE) with speckle tracking strain imaging. Left ventricular (LV) strain, LA reservoir strain (LASr) and LA volume index (LAVI) were measured. LA stiffness index was estimated by the ratio (E/e’)/LASr. ATTR-CA patients were compared to patient with non- CA LVH (interventricular septal thickness &amp;gt; 1.2 cm). Atrial fibrillation (AF) during the TTE was noted. Logistic regression and Cox-regression analyses were performed to find the independent determinant of ATTR-CA and outcome predictors, respectively. Results We studied 98 patients with ATTR-CA (44 with AF) and 62 patients with non-CA LVH (35 with AF). ATTR-CA patients had a higher prevalence of relative apical sparing (RAS) (79% vs 20%, p&amp;lt;0.0001), reduced LASr (9.8±4.8% vs 14.0±7.2%; p&amp;lt;0.001) and high LA stiffness (2.5±0.2 vs 1.4±0.9; p&amp;lt;0.001) irrespective of AF. Surprisingly, LAVI of ATTR-CA patients was significantly lower than non- CA LVH patients (44±15 ml/m2 vs 51±24 ml/m2; p=0.046). Consequently, LAVI correlated strongly with LASr in non-amyloid LVH group (r= -0.52, p&amp;lt;0.001) whereas no correlation was observed in ATTR-CA (p&amp;lt;0.05) (Figure 1). Patients with ATTR-CA had the lowest LASr and highest LA stiffness regardless of AF (Figure 2). Importantly, LASr determined ATTR-CA among all study subjects independently of RAS (p&amp;lt;0.001) and emerged as a predictor of composite endpoint including all-cause mortality, hospitalization from heart failure and stroke in ATTR-CA patients (p=0.037). Conclusion ATTR-CA is characterized by severely reduced LASr and increased LA stiffness, yet LA dilatation is relatively less severe when compared to other causes of LVH. LASr seems promising to make the differential diagnosis of ATTR-CA and is of prognostic importance.Figure 1Figure 2

Abstract 13839: Value of 2D Speckle Tracking Echocardiography in Predicting Short-Term Cardiovascular Outcomes in Multisystem Inflammatory Syndrome in Children: Analysis of the MUSIC Data

Introduction: Cardiovascular (CV) involvement in multisystem inflammatory syndrome in children (MISC) is frequent (80-85%). Data on 2D speckle tracking echocardiography and its value in predicting CV outcomes are limited. Hypothesis: We hypothesized that an association exists between 2D speckle tracking strain/strain rate parameters at admission and adverse CV outcomes during hospitalization (inotropic support, major arrhythmias, cardiac arrest, ECMO, death, or transplant). Methods: We performed a multicenter (33 centers) cohort study on MISC patients hospitalized from 03/2020 to 11/2021 with at least one echocardiogram read by the Core Lab. The association between each 2D speckle tracking strain parameter and adverse CV outcomes was assessed by logistic regression. Results: Of 349 patients (median age 8.7 years [IQR 5.3,12.9]), 122 (35%) had decreased left ventricle (LV) ejection fraction (EF) and 156 (45%) had depressed LV 4-chamber longitudinal strain (LS) or basal circumferential strain (CS) during hospitalization. Worst EF and strain occurred around 5 days of illness. Of those with abnormal LS or CS strain, 50% normalized in ≤1 week, 95% within 50 days. Adverse CV outcomes occurred in 121 (35%) patients. Patients with adverse outcomes were older (p=0.003), more likely to have an underlying metabolic/genetic disorder (p=0.015), abnormal troponin (p&lt;0.001), and higher C-reactive protein (CPR) at admission (p&lt;0.001). They also had higher indexed LV end-diastolic volume (p&lt;0.001) and mass (p=0.015), worse EF (p&lt;0.001), worse LS (p=0.002), and worse CS (p=0.001). When adjusting for days of illness, age, gender, race, obesity, comorbidities, SARS-CoV-2 positivity, CRP, and abnormal troponin at admission, LS Z-score (adjusted OR 1.24 [95% CI 1.03,1.49], AUC 0.754 and longitudinal early diastolic strain rate (LEDSR; adjusted OR 1.98 [IQR 1.18, 3.33], AUC 0.760) at admission were independently associated with adverse CV outcomes. Conclusion: Almost half of the MISC patients had abnormal LS or CS at admission, but the majority recovered quickly. LS and LEDSR at admission were independently associated with adverse CV outcomes. These data may help in early characterization, risk stratification, and prognostication in patients with MISC.

Abstract 16723: Comparison of Myocardial Strain During Active Labor in Parturients With Hypertensive Disorders of Pregnancy via Speckle-Tracking Echocardiography

Introduction: Hypertensive disorders of pregnancy (HDP) are increasing in prevalence in the USA and affect maternal morbidity and mortality. Hypothesis: Echocardiographic strain abnormalities may be more prevalent in patients with HDP in active labor, which may unmask subclinical left ventricular dysfunction. Methods: A total of 59 healthy term parturients (≥37 wks gestational age) in active labor (≥6cm cervical dilation) underwent echocardiography to assess cardiac function during peak physiologic stress. Speckle tracking strain analysis was performed using apical 4-, 3- and 2-chamber views during uterine contraction and relaxation with a S5-1 Philips Sparq probe and analyzed with Qlab 9 strain analysis software (Philips, Andover, MA, USA). Abnormal strain cutoff was &gt;-20%. Mean ± SD summarized continuous variables; absolute and relative frequencies for categorical. Welch T-test and Chi-square were used for group comparisons. Results: HDP was present in 21 subjects and absent in 39. Mean age, parity, and prevalence of diabetes did not differ significantly between the two groups. The HDP group had a higher mean BMI (Table 1). The non-HDP group had strain abnormalities in two segments during uterine relaxation, absent during contraction. The HDP group had abnormalities in 5 segments during uterine relaxation, 4 of which were persistently abnormal during uterine contraction (Fig 1). Conclusions: Abnormal strain values were detected at a higher rate in HDP group than in non-HDP group in active labor. Future research is needed to determine if subclinical strain abnormalities in those with HDP during active labor are predictive of developing future cardiovascular disease.

Experimental Testing and Validation of Adaptive Equalizer Using Machine Learning Algorithm

Due to the increasing demand for high-speed data transmission, wireless communication has become more advanced. Unfortunately, the various kinds of impairments that can occur when carrying data symbols through a wireless channel can affect the network performance. Some of the solutions that are proposed to address these issues include channel equalization, and that can be solved through machine learning techniques. In this paper, a hybrid approach is proposed that combines the features of tracking mode and training mode of adaptive equalizer. This method utilizes the concept of machine learning (ML) to classify different environments (highly, medium, low, open space cluttered) based on the measurements of their RF signal. The results of the study revealed that the proposed method can perform well in real-time deployments. The performance of ML algorithms namely Logistic Regression, KNN Classifier, SVM Classifier, Naive Bayes, Decision Tree classifier and Random Forest classifier is analyzed for different number of samples such as 10, 50 and 100. The performance of these algorithms is evaluated by comparing their accuracy, sensitivity, specificity, F1 score and Confusion Matrix. The objective of this study is to demonstrate that a single ML algorithm cannot perform well in all kinds of environments. In order to choose the best algorithm for a given environment, the decision device has to analyze the various factors that affect the performance of the system. For instance, the random forest classifier performed well in terms of accuracy (100 percent), specificity (100 percent), sensitivity (100 percent), and F1_score (100 percent). On the other hand, the logistic regression algorithm did not perform well in low cluttered environment.

Large scale indoor occupant tracking using distributed acoustic sensing and machine learning

The recent COVID-19 pandemic has brought attention to the criticality of implementing measures to prevent viral transmission and reduce the risk of infection. It is necessary to identify crowd-gathering hazards and implement appropriate engineering control measures. Consequently, obtaining comprehensive footfall information at a large scale becomes significant. Vibration-based sensors are currently the preferred choice for footfall detection, with geophones being the commonly utilized sensors known for their effective performance. However, the deployment of geophones in large-scale scenarios presents challenges due to the substantial amount of manual labor involved. To address these limitations, the Distributed Acoustic Sensing (DAS) system, a non-intrusive sensor, is introduced as an alternative solution. While DAS has been successfully applied in various long-distance scenarios, such as pipeline surveillance and real-time train tracking, its effectiveness in footfall detection requires further evaluation. Therefore, this study proposes a machine learning method to achieve footstep recognition using DAS, considering the inherent time dependency and spatial continuity present in footfall trajectories. To further evaluate the effectiveness of DAS, geophones are selected as the benchmark sensors. The evaluation process encompasses footstep recognition and additional data implementation. The results demonstrate that the proposed recognition method achieves high accuracy for both sensors, thereby establishing DAS as a more applicable solution for footfall detection compared to geophones. In conclusion, DAS offers the advantage of flexible space resolution settings and adaptable deployment options, rendering it suitable for applications in diverse scenarios. Its capabilities make it suitable for large-scale occupancy monitoring scenarios.

Adaptive cooperative control for multiple high-speed trains with uncertainties, input saturations and state constraints

This paper investigates the adaptive cooperative control of multiple high-speed trains, where uncertainties, input saturations and state constraints are considered simultaneously. Within the multi-agent framework, the multi-train system cooperative operation problem is formulated, with the leader train tracks the desired operation trajectory, and the follower trains automatically operate according to the state information of the front train. In order to overcome the parameter uncertainties and unknown external disturbances of the system, a bounded-parameter robust adaptive control (BRAC) method is proposed for speed and position tracking of the leader train. Then a novel state-constraint bounded-parameter robust adaptive controller (SBRAC) is further designed in two steps to avoid the risk of overspeed and collision of the follower trains. The auxiliary dynamic system (ADS) with saturation compensation is introduced to solve input saturations, and the barrier Lyapunov function (BLF) is constructed to actively constrain the speed and position of the trains. Finally, numerical simulations are given for the multi-train system to demonstrate the effectiveness of the theoretical studies.

Laminations and 2-filling rays on infinite type surfaces

The loop graph of an infinite type surface is an infinite diameter hyperbolic graph first studied in detail by Juliette Bavard. An important open problem in the study of infinite type surfaces is to describe the boundary of the loop graph as a space of geodesic laminations. We approach this problem by constructing the first examples of 2-filling rays on infinite type surfaces. Such rays have strong filling properties while failing to correspond to points on the boundary of the loop graph. As such they may be thought of as “fake boundary points.” We give multiple constructions using both a hands-on combinatorial approach and an approach using train tracks and automorphisms of flat surfaces. In addition, our approaches are sufficiently robust to describe all 2-filling rays with certain other basic properties as well as to produce uncountably many distinct mapping class group orbits.