FT-IR spectroscopy of carbon dioxide in CR-39 and SR-90 track detectors irradiated with ions and gamma-rays at different energies and fluences

Two types of polymeric track detectors CR-39 and SR-90 were irradiated with protons, alpha particles, heavy ions and gamma-rays at different energies and fluences. After irradiation these detectors were analyzed with an FT-IR spectrometer of Jasco type 5300 in transmission and ATR modes. We have found that CO₂ is produced not only by irradiation but also by polymerization. The amount of CO₂ in the detector material is closely related to the latent track formation.     

The atomic force microscope as a fine tool for nuclear track studies

Atomic force microscopy (AFM) is a relatively new tool in the study of materials used in the nuclear track methodology. The sensitivity to detect ionizing nuclear particles is strongly influenced by the surface roughness of the material used as detector. In this contribution a surface analysis of several commercial polycarbonates used as nuclear track detectors is presented.     

Tracks in MoS2 irradiated with 20 MeV fullerene and 1 GeV lead ions

The first results of a Transmission Electron Microscopy study of Molybdenite (MoS₂) irradiated with 20 MeV fullerene and 1 GeV lead ions are presented. It is shown that the energy deposited by electronic excitation by both types of projectiles leads to track formation. Although the value of the linear rate of energy deposition is comparable for 20 MeV C₆₀ clusters and 1 GeV Pb ions, the diameters of the tracks created by the clusters is two times greater than the diameter of the tracks induced by 1 GeV Pb ions. Furthermore, the tracks in the sample irradiated with fullerene ions present specific contrast features.     

Qualitative analysis of ion tracks in Makrofol E

The track radius calculation reported by Tombrello was applied to experimental data of tracks from several ions and energies in Makrofol E. Qualitative analysis of ion tracks in this material is discussed. These data were also compared with values calculated using the Continuum Distorted Wave-Eikonal Initial State approximation     

一个经典静电学问题的定量分析

从定量的角度分析了一个经典静电学问题即水珠在静电场中的运动轨迹.运用牛顿定律建立了水珠的运动学方程,并在MATLAB环境下得出方程的数值解,最后通过设计模拟实验系统验证了结果.     

Ion track etching revisited: II. Electronic properties of aged tracks in polymers

We compile here electronic ion track etching effects, such as capacitive-type currents, current spike emission, phase shift, rectification and background currents that eventually emerge upon application of sinusoidal alternating voltages across thin, aged swift heavy ion-irradiated polymer foils during etching. Both capacitive-type currents and current spike emission occur as long as obstacles still prevent a smooth continuous charge carrier passage across the foils. In the case of sufficiently high applied electric fields, these obstacles are overcome by spike emission. These effects vanish upon etchant breakthrough. Subsequent transmitted currents are usually of Ohmic type, but shortly after breakthrough (during the track’ core etching) often still exhibit deviations such as strong positive phase shifts. They stem from very slow charge carrier mobility across the etched ion tracks due to retarding trapping/detrapping processes. Upon etching the track’s penumbra, one occasionally observes a split-up into two transmitted current components, one with positive and another one with negative phase shifts. Usually, these phase shifts vanish when bulk etching starts. Current rectification upon track etching is a very frequent phenomenon. Rectification uses to inverse when core etching ends and penumbra etching begins. When the latter ends, rectification largely vanishes. Occasionally, some residual rectification remains which we attribute to the aged polymeric bulk itself. Last not least, we still consider background currents which often emerge transiently during track etching. We could assign them clearly to differences in the electrochemical potential of the liquids on both sides of the etched polymer foils. Transient relaxation effects during the track etching cause their eventually chaotic behaviour.     

Improving the robustness in railway station areas

In order to improve the robustness of a railway system in station areas, this paper introduces an iterative approach to successively optimize the train routing through station areas and to enhance this solution by applying some changes to the timetable in a tabu search environment. We present our vision on robustness and describe how this vision can be used in practice. By introducing the spread of the trains in the objective function for the route choice and timetabling module, we improve the robustness of a railway system. Using a discrete event simulation model, the performance of our algorithms is evaluated based on a case study for the Brussels’ area. The computational results indicate an average improvement in robustness of 6.2% together with a decrease in delay propagation of about 25%. Furthermore, the effect of some measures like changing the train offer to further increase the robustness is evaluated and compared.     

Coupled chemical reactions in dynamic nanometric confinement: IV. Ion transmission spectrometric analysis of nanofluidic behavior and membrane formation during track etching in polymers

In recent papers, it was shown that coupled chemical-topological reactions (CCRs) with both NaOH etchant and silver salts, performed in thin swift-heavy ion-irradiated polymers under the application of a test voltage across the polymer foils, eventually gave rise to characteristic current/voltage features and Bode plots that were tentatively attributed to the formation of Ag₂O membranes within the etched tracks. The same was also found when replacing the silver ions by lithium ions, and adding fluoride ions to the NaOH etchant, to promote LiF membrane formation. Ion Transmission Spectrometry (ITS) enabled us to reconfirm the existence of these membranes beyond doubt. The membrane thickness was determined to be ～0.2–0.4?µm in the best cases.

ITS also revealed that hitherto membrane formation occurs only in ～1% of all tracks, or even less. The reason for this poor abundance seems to be that the decisive factor for membrane formation, which is the firm anchoring of the emerging solid Ag₂O or LiF reaction products on the etched track walls, was hitherto rarely fulfilled. We attribute this tentatively to the too high test voltage applied for controlling the CCR process that might hinder the product anchoring on the walls by promoting nanofluidic electromigration. Indeed, voltage reduction seems to improve the situation.     

Ion-induced temperature rise in various types of insulators

Swift heavy ions induce a Gaussian temperature distribution Θ(r) in insulators which depend neither on the physical properties of the solid nor on the kind of the projectiles. In this paper, we show that all experimental data suitable for analysis confirm the validity of Θ(r). The same result is obtained for ZrSiO₄, MgAl₂O₄, KTiOPO₄, Al₂O₃ and Y₂O₃, where systematic experiments have not been performed yet. The analysis demonstrates that Θ(r) may be valid in biomolecular targets and in high-T_c superconductors as well. The Fourier equation cannot reproduce the relation Θ(r); thus, it is not suitable for the estimation of the ion-induced temperatures. The consequences of the uniformity in track formation must also affect other radiation-induced effects.     

Multi-train trajectory optimization for energy-efficient timetabling

This paper proposes a novel approach for energy-efficient timetabling by adjusting the running time allocation of given timetables using train trajectory optimization. The approach first converts the arrival and departure times to time window constraints in order to relax the given timetable. Then a train trajectory optimization method is developed to find optimal arrival/departure times and optimal energy-efficient speed profiles within the relaxed time windows. The proposed train trajectory optimization method includes two types, a single-train trajectory optimization (STTO), which focuses on optimizing individual train movements within the relaxed arrival and departure time windows, and a multi-train trajectory optimization (MTTO), which computes multi-train trajectories simultaneously with a shared objective of minimizing multi-train energy consumption and an additional target of eliminating conflicts between trains. The STTO and MTTO are re-formulated as a multiple-phase optimal control problem, which has the advantage of accurately incorporating varying gradients, curves and speed limits and different train routes. The multiple-phase optimal control problem is then solved by a pseudospectral method. The proposed approach is applied in case studies to fine-tune two timetables, for a single-track railway corridor and a double-track corridor of the Dutch railway. The results suggest that the proposed approach is able to improve the energy efficiency of a timetable.