Track Structure Research Articles

Experimental Evaluation of Under Slab Mats (USMs) Made from End-of-Life Tires for Ballastless Tram Track Applications

The growing population of urban areas results in the need to deal with the noise pollution from the transportation system. This study presents experimental test results of static and dynamic elastic characteristics of under slab mats (USMs) according to the procedure of DIN 45673-7. Prototype USMs based on recycled elastomeric materials, i.e., SBR granules and fibres produced from waste car tires, are analysed. Vibration isolation mats with different thicknesses (10, 15, 20, 25, 30, and 40 mm), densities (500 and 600 kg/m3), and different degrees of space filling (no holes, medium holes, large holes) are considered. Moreover, a practical application of the laboratory test results of USMs in the design of ballastless track structures of two different types (with a concrete slab and longitudinal beams) is presented. Deflections of the rail and the floating slab system, as well as stresses acting on the mat, are determined according to EN 16432-2. The use of shredded rubber from recycled car tires as a material component of sustainable and environmentally friendly tram track structures may be one of the most effective ways to manage rubber waste within the current trend toward a circular economy, and this study intends to introduce methods for experimental identification and analytical selection of basic static and dynamic parameters of prototype USMs.

Analysis of sagittal plane cine magnetic resonance imaging for measurement of pancreatic tumor residual motion during breath hold and evaluation of gating margins used in radiotherapy treatment.

In pancreatic radiotherapy, residual tumor motion during treatment increases the risk of toxicity. Cine imaging acquired during magnetic resonance guided radiotherapy (MRgRT) enables real-time treatment gating in response to anatomical motion, which can reduce this risk; however, treatment gating can negatively impact the efficiency of treatment. This study aimed to quantify the extent of residual tumor motion during breath hold and evaluate the appropriateness of the treatment gating margins used in current clinical practice. Cine imaging acquired during pancreatic MRgRT of 11 patients on the ViewRay MRIdian was analyzed. The total duration of treatment analyzed was 12 h 13 min. Improved methods for processing and analyzing cine imaging were developed: breath holds were systematically separated with frequency analysis, residual motion was measured with consideration of both the tracking structure contour and centroid, and residual motion measurements were supported by phantom measurements of image scaling, resolution, and noise. Residual motion was measured at angles 0°, 45°, 90°, and 135° to the superior-inferior (SI) direction. Total residual motion was measured by combining directional measurements. The minimum tracking structure displacement resolvable through cine imaging was found to be 1.5mm; therefore, residual motion analysis was limited to 1.5mm spatial resolution. Total residual motion was contained within margins ±1.5, ±3, and ±4.5mm with mean percentage frequencies of 97.0%, 91.1%, and 67.8%. Most residual motion was observed in the SI direction, and significantly more residual motion was measured for the tracking structure contour than the centroid. The results demonstrate that patients are largely able to maintain breath hold positions to within a 3mm margin, thus provide evidence that supports the use of a 3mm gating margin in clinical practice. Residual motion frequently exceeded 1.5mm so a reduction in gating margin would have an undesirable impact on treatment efficiency.

Monte Carlo damage models of different complexity levels predict similar trends in radiation induced DNA damage

Ion therapies have an increased relative biological effectiveness (RBE) compared to X-rays, but this remains poorly quantified across different radiation qualities. Mechanistic models that simulate DNA damage and repair after irradiation could be used to help better quantify RBE. However, there is large variation in model design with the simulation detail and number of parameters required to accurately predict key biological endpoints remaining unclear. This work investigated damage models with varying detail to determine how different model features impact the predicted DNA damage.

Methods: Damage models of reducing detail were designed in TOPAS-nBio and Medras investigating the inclusion of chemistry, realistic nuclear geometries, single strand break damage, and track structure. The nucleus models were irradiated with 1 Gy of protons across a range of linear energy transfers (LETs). Damage parameters in the models with reduced levels of simulation detail were fit to proton double strand break (DSB) yield predicted by the most detailed model. Irradiation of the optimised models with a range of radiation qualities was then simulated, before undergoing repair in the Medras biological response model.

Results: Simplified damage models optimised to proton exposures predicted similar trends in DNA damage across radiation qualities. On average across radiation qualities, the simplified models experienced an 8% variation in double strand break (DSB) yield but a larger 28% variation in chromosome aberrations. Aberration differences became more prominent at higher LETs, with model features having an increasing impact on the distribution and therefore misrepair of DSBs. However, overall trends remained similar with better agreement likely achievable through repair model optimisation. 

Conclusion: Several model simplifications could be made without compromising key damage yield predictions, although changes in damage complexity and distribution were observed. This suggests simpler, more efficient models may be sufficient for initial radiation damage comparisons, if validated against experimental data.&#xD.

Deriving the Ionospheric Electric Field From the Bulk Motion of Radar Aurora in the E‐Region

AbstractIn the auroral E‐region strong electric fields can create an environment characterized by fast plasma drifts. These fields lead to strong Hall currents which trigger small‐scale plasma instabilities that evolve into turbulence. Radio waves transmitted by radars are scattered off of this turbulence, giving rise to the ‘radar aurora’. However, the Doppler shift from the scattered signal does not describe the F‐region plasma flow, the drift imposed by the magnetosphere. Instead, the radar aurora Doppler shift is typically limited by nonlinear processes to not exceed the local ion‐acoustic speed of the E‐region. This being stated, recent advances in radar interferometry enable the tracking of the bulk motion of the radar aurora, which can be quite different and is typically larger than the motion inferred from the Doppler shift retrieved from turbulence scatter. We argue that the bulk motion inferred from the radar aurora tracks the motion of turbulent source regions (provided by auroras). This allows us to retrieve the electric field responsible for the motion of field tubes involved in auroral particle precipitation, since the precipitating electrons must drift. Through a number of case studies, as well as a statistical analysis, we demonstrate that, as a result, the radar aurora bulk motion is closely associated with the high‐latitude convection electric field. We conclude that, while still in need of further refinement, the method of tracking structures in the radar aurora has the potential to provide reliable estimates of the ionospheric electric field that are consistent with nature.

Modeling of railway track integrating a shock-absorbing mat at the sleepers-ballast interface using eigenfunctions of displacement

Damage caused to railway tracks and the surrounding environment during trains passage have become a real concern for those involved in the railway sector over the years. To find a solution for this problem, several approaches have already been implemented on railway tracks in some countries. Despite the efforts made in this area, the problem of ground vibration induced by railway traffic still remains a concern. Therefore, many studies have been focused on solutions to attenuate, even cancel vibrations effects on the track and nearby environment. This work has presented a modeling of a ballasted railway track with a shock-absorbing mat or Under Sleepers Rubber Mat (USRm) at the sleepers/ ballast interface. Using the equation of wave propagation in the ground and the constitutive law, the eigenfunctions of the displacement vector were determined. By coupling the equations of the track and those of the ground, the displacement, the velocity, and the acceleration of each track component, as well as the stress on the ground surface were expressed. The Newmark numerical method was used to represent these variables and to highlight the (USRm) influence on the dynamic behavior of the different track component. Comparison of the results obtained with the proposed railway model shows a reduction in vibration amplitudes of 64.9% and 94%for the rail, 86.5% and 56.25% for the sleepers. At the ground surface, the attenuation of vibration is evaluated at 53% and 6.85%, respectively for linear and nonlinear cases. The insertion of the shock-absorbing mat (USRm) in the railway track structure also reduces stress at the ground surface. The configuration of the railway track with a damping mat (USRm) therefore significantly reduces the transmitted vibration to the ground and to the nearby structures. It also contributes to the stability of the track and the improvement of its performance. The proposed railway track model with a shock-absorbing mat can be considered as a solution to reduce vibrations generated on track and the ground during trains passages.

Impact of typical environments in China's western mountainous areas on the durability of railway concrete: a review

PurposeThis study aims to analyze the impact mechanism of typical environments in China's western mountainous areas on the durability of railway concrete and propose measures to improve durability.Design/methodology/approachWith the continuous promotion of infrastructure construction, the focus of China's railway construction has gradually shifted to the western region. The four typical environments of large temperature differences, strong winds and dryness, high cold and low air pressure unique to the western mountainous areas of China have adverse effects on the durability of typical railway structure concrete (bridges, ballastless tracks and tunnels). This study identified the characteristics of four typical environments in the western mountainous areas of China through on-site research. The impact mechanism of the four typical environments on the durability of concrete in different structural parts of railways has been explored through theoretical analysis and experimental research; Finally, a strategy for improving the durability of railway concrete suitable for the western mountainous areas of China was proposed.FindingsThe daily temperature difference in the western mountainous areas of China is more than twice that of the plain region, which will lead to significant temperature deformation and stress in the multi-layered structure of railway ballastless tracks. It will result in cracking. The wind speed in the western plateau region is about 2.5 to 3 times that of the plain region, and the average annual rainfall is only 1/5 of that in the plain region. The drying effect on the surface of casting concrete will significantly accelerate its cracking process, leading to serious durability problems. The environmental temperature in the western mountainous areas of China is generally low, and there are more freeze-thaw cycles, which will increase the risk of freeze-thaw damage to railway concrete. The environmental air pressure in the western plateau region is only 60% of that in the plain region. The moisture inside the concrete is more likely to diffuse into the surrounding environment under the pressure difference, resulting in greater water loss and shrinkage deformation of the concrete in the plateau region. The above four issues will collectively lead to the rapid deterioration of concrete durability in the western plateau region. The corresponding durability improvement suggestions from theoretical research, new technology development and standard system was proposed in this paper.Originality/valueThe research can provide the mechanism of durability degradation of railway concrete in the western mountainous areas of China and corresponding improvement strategies.

Research on extreme value estimations and dynamic coefficients of wheel load for high-speed railway based on generalized Pareto distribution theory

The design value of wheel load is one of the key design parameters for high-speed railway ballastless track structure, which essentially belongs to the extreme estimation of wheel load. Based on the generalized Pareto distribution theory, this article carries on the research on the extreme value estimations of wheel load excited by whole wavelength range irregularity, which provides a basis for the design of ballastless track structure. When using automatic threshold selection method, sample declustering can improve the independence between data. The shape parameter screening method is proposed for the extreme value estimations of wheel load, and the corresponding sample size and shape parameter range for each cluster are determined. A reasonable sample size is determined, and the mean of the extreme estimations of wheel load is used as the final extreme estimation of wheel load. The dynamic coefficients that match the design life of the ballastless track structure are obtained.

Evaluation of railway noise calculation models using CNOSSOS-EU considering the effect of rail roughness

Railway noise assessment is an important tool in decision-making for urban planning, investment in transportation infrastructure and implementation of noise reduction strategies. Currently, the procedure is based on CNOSSOS-EU (Common Noise Assessment Methods in Europe), which was developed in accordance with European Directive 2002/49/EC. This method takes into account a variety of factors impacting rail noise levels, such as vehicle characteristics and track features. The purpose of this study was to investigate the influence of rail roughness on generated railway noise and to evaluate the accuracy of calculation models using CNOSSOS-EU. The study involved in-situ railway noise measurements at three different locations near the city of Zagreb, Croatia, and measuring rail roughness at each location. In order to eliminate the influence of other factors, the rail track structures at the measurement locations were similar, and an identical train configuration was used for the study. Finally, a comparison was made between calculation models based on default roughness values and models including values obtained from in-situ measurements. This approach enabled an assessment of the variations in CNOSSOS-EU calculation models taking into account actual in-situ rail roughness measurements.

Automated Identification of Clinically Relevant Regions in Glaucoma OCT Reports Using Expert Eye Tracking Data and Deep Learning.

To propose a deep learning-based approach for predicting the most-fixated regions on optical coherence tomography (OCT) reports using eye tracking data of ophthalmologists, assisting them in finding medically salient image regions. We collected eye tracking data of ophthalmology residents, fellows, and faculty as they viewed OCT reports to detect glaucoma. We used a U-Net model as the deep learning backbone and quantized eye tracking coordinates by dividing the input report into an 11 × 11 grid. The model was trained to predict the grids on which fixations would land in unseen OCT reports. We investigated the contribution of different variables, including the viewer's level of expertise, model architecture, and number of eye gaze patterns included in training. Our approach predicted most-fixated regions in OCT reports with precision of 0.723, recall of 0.562, and f1-score of 0.609. We found that using a grid-based eye tracking structure enabled efficient training and using a U-Net backbone led to the best performance. Our approach has the potential to assist ophthalmologists in diagnosing glaucoma by predicting the most medically salient regions on OCT reports. Our study suggests the value of eye tracking in guiding deep learning algorithms toward informative regions when experts may not be accessible. By suggesting important OCT report regions for a glaucoma diagnosis, our model could aid in medical education and serve as a precursor for self-supervised deep learning approaches to expedite early detection of irreversible vision loss owing to glaucoma.

Research and prediction of early-age loads in double-block ballastless track structure

Considering the hydration reaction of cement, a finite element model(FEM) of the coupling of temperature and humidity field and chemical field in the early age of the double-block ballastless track structure was established, and a field monitoring test on the early age of track slab was carried out with the newly constructed Fuzhou-Xiamen high-speed railway line as a case to verify the correctness of the FEM. Based on the official meteorological data from China Meteorological Administration (CMA) and the FEM, the dataset of vertical temperature and humidity gradients in the early age of the track slab was constructed, and five machine learning training models, namely, machine learning (MLR), multivariate polynomial regression (MPR), support vector regression (SVR), random forest (RF), and gradient boosted regression (GBR), were adopted to train the temperature gradient model and humidity gradient model for the early age of the track slab. The research results show that: (1) under the combined effect of solar radiation, convective heat transfer, radiative heat exchange and the cement hydration reaction, the temperature loading leads to the susceptibility of the sleepers to diagonal cracking; the humidity loading leads to transverse cracking in the center region of the surface of the track slab; (2) the finite element model with a higher accuracy provided the training dataset for the machine learning model. According to the Spearman correlation coefficient, the input features of the temperature gradient model and the humidity gradient model are determined, respectively; (3) Five ML methods were used to train the temperature gradient model and humidity gradient model, both of which demonstrated good generalization ability with a coefficient of determination(R2) greater than 0.85. Among these methods, GBR and SVR exhibited the best performance; From the perspective of MAPE value, the prediction effect of the temperature gradient training model was better than that of the humidity gradient training model; (4) The curing method and the average value of the relative humidity were the important input features influencing the training models for the temperature and humidity gradient loads, respectively. This finding provided an important guideline for the construction of ballastless track structures.

Nanodosimetric investigation of the track structure of therapeutic carbon ion radiation part 1: measurement of ionization cluster size distributions

At the Heidelberg Ion-Beam Therapy Center, the track structure of carbon ions of therapeutic energy after penetrating layers of simulated tissue was investigated for the first time. Measurements were conducted with carbon ion beams of different energies and polymethyl methacrylate (PMMA) absorbers of different thicknesses to realize different depths in the phantom along the pristine Bragg peak. Ionization cluster size (ICS) distributions resulting from the mixed radiation field behind the PMMA absorbers were measured using an ion-counting nanodosimeter. Two different measurements were carried out: (i) variation of the PMMA absorber thickness with constant carbon ion beam energy and (ii) combined variation of PMMA absorber thickness and carbon ion beam energy such that the kinetic energy of the carbon ions in the target volume is constant. The data analysis revealed unexpectedly high mean ICS values compared to stopping power calculations and the data measured at lower energies in earlier work. This suggests that in the measurements the carbon ion kinetic energies behind the PMMA absorber may have deviated considerably from the expected values obtained by the calculations. In addition, the results indicate the presence of a marked contribution of nuclear fragments to the measured ICS distributions, especially if the carbon ion does not cross the target volume.

CONSTRUCTION OF THE RAILWAY TRACK OF UKRAINE AND PROSPECTS FOR THEIR IMPROVEMENT

The goal. The process of improving the design of the railway track requires a detailed study of the history of the development of its structural elements, methods of combination, interconnections and limits of mutual influence. Modern track designs are the result of many years of hard work by scientists and long operational tests. Some designs were inventions at the time, some were breakthrough technologies, some remained just ideas, and some have existed for more than a century. The study of the history of the development of railway track structures and modern existing structures in operation made it possible to identify a promising direction for improvement and further development, taking into account the existing problems on the mainline transport tracks and industrial enterprise tracks. Reinforced concrete sleepers and intermediate fasteners that allow for track gauge adjustment are the railroad track structure that should be improved in the coming years. Improving railroad track design is a continuous process in the development of rail transport. Recently, new track designs have been introduced on Ukrainian railways. As a rule, the problems of track facilities are first considered and technical tasks are formulated. Then, a public discussion is held in the scientific and practical environment and an appropriate development strategy is born. Such a strategy is reviewed and approved at scientific and technical meetings and specialized commissions. This article aims to identify promising areas for improving the track design and solving the problems of installing and operating a continuous track by analyzing existing designs and world experience of railways. Methods. Methods of scientific analysis and synthesis of track development design, methods of analytical geometry. Results. Based on the analysis of the history of the development of the railroad track structure and modern designs, a promising direction of improvement is proposed. A promising railroad track structure is defined as a reinforced concrete sleeper and fasteners capable of forming an adjustable track gauge of up to 1545 mm. At the same time, it is necessary that the new design has sufficient stability of the jointless track plates. Practical significance. The application of the proposed structure within small radius curves, provided that the results of trial operation and testing of the established procedure are positive, will reduce the operating costs associated with the current maintenance of the tracks, expand the scope of laying of the jointless track and use reinforced concrete sleepers in small radius curves at industrial enterprises.

STUDY OF THE DESIGN OF RAILWAY TRACKS OF INDUSTRIAL ENTERPRISES WITHIN THE AREAS OF SMOOTH TRACK EXPANSION

The goal. Railway sidings of industrial enterprises are the shippers and receivers of goods, which determine their main nomenclature for transportation by mainline rail transport. The length of railway sidings of industrial enterprises varies widely, from a few hundred meters to hundreds of kilometers, including the length of the siding of PJSC ArcelorMittal Kryvyi Rih exceeding 700 km. The combination of factors such as the presence of technological transportation on the sidings, the development of the industrial enterprises' transportation system over time, and the master plan of the main production facilities leads to the need to apply railway transport design standards for severe and especially severe conditions. This is mainly expressed in reducing the radii of curved track sections to the minimum possible values. When using reinforced concrete sleepers of the Sh6 type, it is possible to arrange a track gauge of 1539 mm in curved sections. But currently, there is no approved design for smooth track widening sections on reinforced concrete sleepers in front of curves with radii of less than 300 meters. There is also a reasonable need to increase the track gauge to at least 1540 mm in curves of such radii. Together with the limited service life of wooden sleepers when they are laid in areas of smooth track widening compared to reinforced concrete sleepers, this necessitates the development of a track structure on reinforced concrete sleepers within the area of smooth track widening. Methods. Methods of scientific analysis and synthesis of the track development structure, methods of analytical geometry. Results. Based on the analysis of the design of intermediate fasteners of the KB50 type, the design of a section of smooth track widening using reinforced concrete sleepers of types Sh1-1 and Sh6 and rails R50 is proposed. The track widening from 1520 to 1545 mm is achieved by developing the order of laying sleepers of different types and turning the KB50 substrates. In this case, the length of the section of smooth track widening from 1520 mm to 1545 mm is 2800 mm, and the actual deviation is 8.9‰. Practical significance. The use of the considered structure within the areas of smooth track widening, provided that the results of trial operation and testing of the established procedure are positive, will reduce the operating costs associated with the current maintenance of industrial enterprises' tracks, the parameter of which correspond to severe and especially severe design conditions.

Research on damage characteristics and contact interface evolution behavior of double-block ballastless track considering tunnel floor heave

Excessive railway tunnel floor heave (TFH) will reduce the durability of the track structure and jeopardize train operation safety. The TFH characteristics were fitted into cosine and bilinear curves according to the monitoring data. A nonlinear failure analysis model of double-block ballastless track under TFH was established. The deformation transfer law, structural damage mechanism and the interlayer bonding interface failure evolution of the track structure under different TFH characteristics were explored. The results show that the deformation of TFH can be well mapped to the track. The amplitude transfer ratio is less than 100 %. The maximum wavelength transfer ratio under the cosine and bilinear TFH is 129.3 % and 127.5 %, respectively. To avoid the damage of track structure, when the wavelength is 10 m, the amplitude of cosine and bilinear TFH should be controlled at 2.5 mm and 0.5 mm respectively. When the wavelength is greater than 10 m, the amplitude can be appropriately increased. To avoid interlayer bonding cracking, the cosine and bilinear amplitudes with a wavelength of 10 m should be controlled at 5 mm and 1.5 mm, respectively. The track-tunnel interlayer debonding failure under the cosine curve occurs at the edge of the TFH, while the bilinear curve occurs at the center and edge of the TFH. The gaps under the cosine and bilinear TFH exhibit double-peak and multi-peak shapes, respectively. This study can provide theoretical guidance for controlling the performance degradation of track structure caused by TFH.

Effects of Track Structure Nonlinearity on Running Safety of Simply Supported Girder Bridges during Earthquakes

Effects of Track Structure Nonlinearity on Running Safety of Simply Supported Girder Bridges during Earthquakes

TSFormer: Tracking Structure Transformer for Image Inpainting

TSFormer: Tracking Structure Transformer for Image Inpainting

Quantifying the impact of rail longitudinal level changes on dynamic load magnitudes through instrumented wheelset measurements

Track geometry significantly influences train-track dynamic interactions, primarily due to irregularities at the wheel-rail interface. These irregularities generate dynamic load excitations, leading to defects and damage. This study evaluates how track surface profile longitudinal level vertical changes affect vertical wheel-to-rail loads, quantified by the dynamic load factor ( ϕ ), due to the importance of ϕ in track design. A limitation of the existing studies is their focus on instrumented sections and numerical modellings without considering different track structures. This study conducted dynamic load measurements using two instrumented wheelsets (IWS) over a 340 km section operated by a North American Class 1 freight railway in the Canadian Prairies under various track structures and train speeds. Rail surface longitudinal level measurements were obtained as routine measurements through a track geometry car. The paper presents statistical distributions of rail longitudinal level across different track structures and evaluates two widely used and recently developed ϕ equations within the context of North American freight railways to quantify the impact of rail longitudinal level (i.e. profile) changes on dynamic load magnitudes. The study also evaluates regulated threshold values by considering observed trends in the measured data, which aims to quantify and compare these values with our current understanding.

Research on information extension of mountainous rack railway engineering based on IFC standard

In response to the practical demands for data sharing and exchange in the field of rack railway systems engineering, as well as to address the gaps in the rack railway domain within the framework of the IFC4 standard, we extend and define the rack railway domain through entity extension and custom attribute sets. By utilizing the ongoing construction of the Dujiangyan to Mount Siguniang Railway as a case study, we validate the utility of this IFC extension and modeling approach. Leveraging IfcOpenShell, we incorporate the extended data content into the generated IFC file. We present a process for extension tailored to the characteristics of rack railway engineering. This study aims to provide broader information support for the digital construction of track structures in the design phase of rack railway engineering and to facilitate more efficient data exchange and sharing.

Effect of Tunnel Floor Heave on the Deformation and Damage Behavior of Ballastless Track Structures in High-Speed Railways

The extensive development of high-speed railways in mountainous areas has underscored the significant challenge posed by tunnel floor heave, affecting the operational reliability of ballastless tracks. Such heave induces track deformation and structural impairments, critically undermining the operational safety and track serviceability. This investigation enhances the understanding of ballastless tracks’ mechanical responses to tunnel floor heave by introducing a sophisticated nonlinear analytical model that encapsulates the interplay between the track system, tunnel infrastructure, and the encasing geological environment. Utilizing the concrete damaged plasticity approach to model the track’s concrete structure, this research integrates these parameters with the track’s numerical representation, taking into account the role of internal reinforcement. Through an in-depth examination of track deformation, the interstitial gap, and damage progression within the track, it is demonstrated that comprehensive consideration of both the material’s constitutive model and reinforcement structuring is imperative. The analysis results indicate that the heave’s amplitude and wavelength exert limited influence on the deformation amplitude ratio, whereas variations in heave characteristics significantly alter the wavelength transmission ratio, engendering a distinct “M” shaped gap profile. It is observed that the propensity for material damage escalates in areas experiencing pronounced tensile stress, particularly under conditions of reduced wavelength and increased amplitude heave, necessitating prioritized attention in track maintenance protocols.

Radial dependence of ionization clustering around a gold nanoparticle irradiated by X-rays under charged particle equilibrium

Objective.This work explores the enhancement of ionization clustering and its radial dependence around a gold nanoparticle (NP), indicative of the induction of DNA lesions, a potential trigger for cell-death.Approach.Monte Carlo track structure simulations were performed to determine (a) the spectral fluence of incident photons and electrons in water around a gold NP under charged particle equilibrium conditions and (b) the density of ionization clusters produced on average as well as conditional on the occurrence of at least one interaction in the NP using Associated Volume Clustering. Absorbed dose was determined for comparison with a recent benchmark intercomparison. Reported quantities are normalized to primary fluence, allowing to establish a connection to macroscopic dosimetric quantities.Main results.The modification of the electron spectral fluence by the gold NP is minor and mainly occurs at low energies. The net fluence of electrons emitted from the NP is dominated by electrons resulting from photon interactions. Similar to the known dose enhancement, increased ionization clustering is limited to a distance from the NP surface of up to200nm. The number of clusters per energy imparted is increased at distances of up to150nm, and accordingly the enhancement in clustering notably surpasses that of dose enhancement. Smaller NPs cause noticeable peaks in the conditional frequency of clusters between50nm-100nmfrom the NP surface.Significance.This work shows that low energy electrons emitted by NPs lead to an increase of ionization clustering in their vicinity exceeding that of energy imparted. While the electron component of the radiation field plays an important role in determining the background contribution to ionization clustering and energy imparted, the dosimetric effects of NPs are governed by the interplay of secondary electron production by photon interaction and their ability to leave the NP.