Quantitative estimation of track segment yields of water radiolysis species under heavy ions around Bragg peak energies using Geant4-DNA

We evaluate the track segment yield G′ of typical water radiolysis products (eaq−, ·OH and H2O2) under heavy ions (He, C and Fe ions) using a Monte Carlo simulation code in the Geant4-DNA. Furthermore, we reproduce experimental results of ·OH of He and C ions around the Bragg peak energies (< 6 MeV/u). In the relatively high energy region (e.g., > 10 MeV/u), the simulation results using Geant4-DNA have agreed with experimental results. However, the G-values of water radiolysis species have not been properly evaluated around the Bragg peak energies, at which high ionizing density can be expected. Around the Bragg peak energy, dense continuous secondary products are generated, so that it is necessary to simulate the radical–radical reaction more accurately. To do so, we added the role of secondary products formed by irradiation. Consequently, our simulation results are in good agreement with experimental results and previous simulations not only in the high-energy region but also around the Bragg peak. Several future issues are also discussed regarding the roles of fragmentation and multi-ionization to realize more realistic simulations.

EFFECTIVE BATON EXCHANGE IN THE 4X100 M RELAY RACE

Baton exchange effectiveness and speed are essential to performance in sprint relay races, often deciding team victory. An effective baton exchange requires athletes to complete it while at full speed, both by the incoming and the outgoing athlete. Our research aimed to determine the relationship between baton exchange time and the point in the exchange zone where the handoff is completed. The study was carried out among Polish national team sprinters (n=27), competing in the 4x100 m relays. We analyzed 168 men’s and 62 women’s baton exchanges across the annual training cycle. In a 30-meter track segment corresponding to the baton exchange zone, we measured the time the baton spent in this segment (exchange time, ET), using the Brower Timing Systems (TC-System, USA), and the exact point of the baton handoff in this zone (handoff point, HP). To show the relationship between ET and HP, we performed a linear regression analysis. We have found that the further the HP the shorter the ET. This dependence is more evident in women (r=-0.66, r2=0.44 for 1st and 3rd exchanges, and r=-0.72, r2=0.52 for 2nd exchange; both P<0.001) than in men (r=-0.45, r2=0.20 and r=-0.68, r2=0.46; both P<0.001, respectively). The results suggest that the further the baton exchange takes place in the exchange zone (longer HP distance) the more effective the exchange (shorter ET). However, the coefficient of determination ranging (r2=0.20-0.52) indicates that HP explains at most 50% of the ET, and other factors should be taken into account. Nonetheless, the measuring technique proposed by us can provide coaches with additional data on baton exchange effectiveness and athletes' speed abilities.

A Pattern Recognition Algorithm for Quantum Annealers

The reconstruction of charged particles will be a key computing challenge for the high-luminosity Large Hadron Collider (HL-LHC) where increased data rates lead to a large increase in running time for current pattern recognition algorithms. An alternative approach explored here expresses pattern recognition as a quadratic unconstrained binary optimization (QUBO), which allows algorithms to be run on classical and quantum annealers. While the overall timing of the proposed approach and its scaling has still to be measured and studied, we demonstrate that, in terms of efficiency and purity, the same physics performance of the LHC tracking algorithms can be achieved. More research will be needed to achieve comparable performance in HL-LHC conditions, as increasing track density decreases the purity of the QUBO track segment classifier.

Increasing Robustness by Reallocating the Margins in the Timetable

It is a common practice to improve the punctuality of a railway service by the addition of time margins during the planning process of a timetable. Due to the capacity constraints of the railway network, a limited amount of time margins can be inserted. The paper presents a model and heuristic technique to find the better position for the limited amount of time margins (headway buffers and running time supplements) in a train timetable. The aim of reallocating the time margins is to adjust an existing timetable to minimize the sum of train delays at the event of the operational disturbances. The model consists of two basic parts. Firstly, the paper treats the train timetable as a Directed Arc Graph (DAG) with the aggregation concept and proposes a heuristic technique known as Critical Time Margins Allocation (CTMA), which is based on the critical path method (CPM), to reallocate the time margins. Secondly, the paper evaluates the original and modified timetable under different disturbed situations. The case study is developed on a hypothetical small railway network and a practical timetable of single-line train timetable for the track segment of Rawalpindi to Lalamusa, Pakistan. The results show that the timetable modified with the CTMA reduces the total delay time by an average of 3.25% for the small railway network and 5.18% for the large dataset. It suggests that adding the time supplements to the proper positions in a timetable can reduce the delay propagation and increase the robustness of the timetable.

Out-of-Plane Responses of Overspeeding High-Speed Train on Curved Track

This paper presents a numerical study on the out-of-plane responses of a high-speed train running on a curved railway track segment using the moving element method. The accuracy and efficiency of the proposed computation model presented herein are compared with available analytical results from the literature and a finite element solver based on a simplified moving load model. Thereafter, a half-railcar moving sprung-mass model and a double-rail track-foundation model are presented to investigate the behavior of a high-speed train traversing a curved track, particularly when the train speed is greater than the design speed of the curved track segment. The results show that the train speed and severity of track irregularity significantly affect the contact forces on the rails. This paper also presents a case of a railcar overturning when the train speed is greater than 2.5 times the design speed of a curved track segment.