Rutting prediction models are essential elements of efficient pavement management systems. Accuracy of commonly used predictive models necessitates knowledge of the input parameters that they ...incorporate and local calibration of the model coefficients. This study aims at developing a rutting prediction model that incorporates a limited number of inputs, yet is able to accommodate, with sufficient generalisation abilities, to the data scarcity and resource limitations in developing countries. The prediction model is developed by employing deep neural network techniques (DNN) on data extracted from the Long-Term Pavement Performance (LTPP) database. The predictive capability of the DNN model is compared to those of the state-of-the-practice and a multivariate linear regression model fitted using the same dataset. It is found that the DNN rutting prediction model features enhanced predictive power compared to commonly used models in the literature. In addition to predicting pavement rutting, the developed model is further utilised to assess and rank the relative impact of the different model inputs on rutting. The sensitivity analysis results confirm the high influence of traffic and climatic conditions. Moreover, generic family rutting predictive curves corresponding to specific traffic, climate, and performance combinations are developed to render rutting predictions available to all road agencies.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
An intense positron sources is a demanding element in the design of future lepton colliders. A crystal-based hybrid positron source could be an alternative to a more conventional scheme based on the ...electron conversion into positron in a thick amorphous target. The conceptual idea of the hybrid source is to have two separate objects, a photon radiator and a photon-to-positron converter target. In such a scheme an electron beam crosses a thin axially oriented crystal with the emission of a channeling radiation, characterized by a considerably larger amount of photons if compared to Bremsstrahlung. The net result is an increase in the number of produced positrons at the converter target. In this paper we present the results of a beam test conducted at the DESY TB 21 with 5.6 GeV electron beam and a crystalline tungsten radiator. Experimental data clearly highlight an increased production of photons and they are critically compared with the outcomes of novel method to simulate the number of radiated photons, showing a very good agreement. Strong of this, the developed simulation tool has been exploited to design a simple scheme for a positron source based on oriented crystal, demonstrating the advantages in terms of reduction of both deposited energy and the peak energy deposition density if compared to conventional sources. The presented work opens the way for a realistic and detailed design of a hybrid crystal-based positron source for future lepton colliders.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
AbstractThis paper describes the behavior of geogrid–reinforced concrete members. The application of geogrids in concrete constitutes a new dimension for using geosynthetics in infrastructure. In ...pavement applications, geogrids have been used to provide confinement, stabilization, and reinforcement of unbound and asphalt concrete layers, as well as interlayers to mitigate reflective cracking. The ultimate objective of studying the behavior of geogrids in concrete members is to assess the feasibility and benefit of using geogrids in thin concrete overlays. The experimental program consisted of testing 21 simply supported plain and geogrid–reinforced beam specimens under four-point bending. The test parameters included three types of geogrids with different aperture shapes, physical and mechanical properties, and material composition. Additionally, two Portland cement concrete mixtures were used: normal and high strength. Results from testing confirm the reinforcing benefit of the geogrids as evidenced from the load-deflection response in terms of postpeak behavior, load capacity, crack mouth opening displacement (CMOD), and failure mode. Conclusions regarding correlations between the failure properties and the properties of the geogrid are made.
Abstract
For the Future Circular Collider (FCC-ee), particular attention is drawn to the crucial role of the positron source. Two positron production schemes are considered for the FCC-ee: the ...conventional scheme and the crystal-based (hybrid) scheme that involves channelling radiation in the oriented crystals. A start-to-end simulation toolkit should be developed to design and optimize positron production and capture by considering the positron injector parameters, including the electron drive beam and final system acceptance. This paper presents the first results of benchmarking the FCC-ee positron source simulation tools using the SuperKEKB positron source currently in operation. The model starts with the production of positrons and target studies in Geant4. Then, the RF-Track code is used to capture and track the generated positrons through the capture section composed of a matching device and several accelerating structures embedded in the solenoid field to accelerate the positrons up to 120 MeV. After that, the positrons are further accelerated up to the energy of the Damping Ring (1.1 GeV). Finally, the SuperKEKB capture system is applied to the FCC-ee positron injector within the framework of the design studies.
Abstract
Positron sources are the key elements for the future and
current lepton collider projects such as ILC, CLIC, SuperKEKB,
FCC-ee, Muon Collider/LEMMA, etc., introducing challenging critical
...requirements for high intensity and low emittance beams in order to
achieve high luminosity. In fact, due to their large production
emittance and constraints given by the target thermal load, the main
collider parameters such as the peak and average current, the
emittances, the damping time, the repetition frequency and
consequently the luminosity are determined by the positron beam
characteristics. In this paper, the conventional positron sources
and their main properties are explored for giving an indication to
the challenges that apply during the design of the advanced
accelerator concepts. The photon-driven positron sources as the
novel approach proposed, primarily for the future linear colliders,
are described highlighting their variety and problematic.
Classical and quantum properties of scattering of ultrarelativistic electrons in ultrathin crystals are considered. A comparison is made of these two ways of study of scattering process. In classical ...consideration we remark the appearance of sharp peaks in angular distribution of scattered particles, that is treated as a manifestation of the rainbow scattering phenomenon, and in quantum case we show sharp peaks in the angular distribution that arise from the interference of single electrons on numerous crystal planes and can be expressed in terms of reciprocal lattice vectors. We show that for some parameters the quantum predictions substantially differ from the classical ones. The influence of beam divergence on the possibility of experimental observation of the studied effects is estimated.
Geogrid is a geosynthetic material commonly used for soil stability purposes in road embankments and reinforced earth walls due to its tensile reinforcing capability. Recent research has shown the ...efficiency of Geogrid as an internal reinforced concrete column confinement that increases significantly the ductility, but slightly decreases the axial compressive strength of the column. The study reported in this paper investigated the feasibility of using geogrids as external column confinement. It was important to compare external geogrid confinement with internal geogrid confinement on one hand and with bitumen coated E-glass textile sheets on the other. A total of 22 small-scale reinforced concrete (RC) column specimens were tested under uniaxial compression. Each specimen had a 240 mm diameter, 500 mm length, and was reinforced with four 10 mm longitudinal bars confined with three 6 mm ties spaced at 200 mm. The test variables were the confinement material (Geogrid, or Bitumen coated E-glass textile), type of geogrid (uniaxial or biaxial), number of confinement layers (one or two), and confinement location (internal or external). Assessment of the variables was done by analyzing the axial load-displacement behavior, the modes of failure, and the structural ductility measured by fracture energy and energy dissipation. Available analytical models for FRP confined specimens were modified to be applicable to the tested geogrid and bitumen textile confined specimens. A performance-to-cost analysis was also conducted. Results showed that external confinement of reinforced concrete columns using geogrid significantly enhanced the strength, ductility, and energy capacity of the tested specimens.
The study presents a framework for assessing the sustainability of different types of asphalt materials and technologies. The framework is demonstrated through a case study for evaluating the ...sustainability of warm mix asphalt (WMA) mixtures in hot climatic conditions. While various life-cycle assessment (LCA) tools and methodologies have been used for sustainability assessment of WMA from the material production phase to the construction phase, most neglect the maintenance, rehabilitation and end of life phases, based on the assumption that the performance of WMA is similar to that of hot mix asphalt (HMA). This study examines asphalt mix properties and performance indices, and studies their impact on maintenance and rehabilitation schedules when incorporated in a pavement structure, and subsequently life-cycle environmental and economic costs. The study concludes that the assessment outcomes of the LCA and life-cycle cost analysis are heavily affected by the performance measure used to predict the maintenance and rehabilitation schedule or change in service life. For the conditions assumed in the study, WMA mixes yield more favourable environmental and economic results compared to control HMA mixes with unmodified binder.
The Future Circular e + e − Collider pre-injector chain consists of a 6 GeV S-Band linac, a damping ring at 1.54 GeV and pre-booster ring to reach 20 GeV for injection to the main booster. The ...electron and positron beams use the same accelerator chain alternatively. The e −beam is generated from a novel low level RF-gun providing 6.5 nC charge at 11 MeV with 0.5 micron geometric emittance. The e + beam is produced by the impact of a 4.46 GeV e − beam onto a hybrid target, accelerated in the linac up to 1.54 GeV, and injected to the damping ring for emittance cooling. Simulations on the performance of the DR are presented for reaching the required equilibrium emittances at the required damping time. As an alternative option, a 20 GeV linac is considered utilising C-Band cavities and simulations studies have been undertaken regarding the beam transport and transmission efficiency up to that energy.
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