Search results for "stiffness"
showing 10 items of 524 documents
Bitumen stabilized ballast: a potential solution for railway track-bed
2016
Railway ballast degradation under dynamic loads progressively leads to loss of mechanical performance and geometry of the track, so that maintenance interventions are frequently needed. In order to system- atically avoid this issue, recently solutions have been proposed to reinforce track-bed by using polyur- ethane and/or resins as well as asphalt layers among others. Nonetheless, their main limitations are related to the high initial cost and low productivity. To cope with these limitations, in this study, bitumen stabilized ballast (BSB) is proposed as a new solu- tion for ballast stabilization. This method aims at improving durability and reducing settlement by mod- ifying both stiffnes…
Optimización de las propiedades de emulsión de betún para la estabilización de balasto
2017
Ballasted track, while providing economical and practical advantages, is associated with high costs and material consumption due to frequent maintenance. More sustainable alternatives to conventional ballasted trackbeds should therefore aim at extending its durability, particularly considering ongoing increases in traffic speed and loads. In this regard, the authors have investigated a solution consisting of bitumen stabilised ballast (BSB), designed to be used for new trackbeds as well as in reinforcing existing ones. This study presents the idea behind the technology and then focuses on a specific part of its development: the optimisation of bitumen emulsion properties and dosage in relat…
Use of bitumen-stabilised ballast for improving railway trackbed conventional maintenance
2018
Despite its many advantages, ballasted track needs frequent maintenance to ensure an adequate quality of service. However, tamping, traditionally used to correct geometry, causes ballast degradation and loosening of the already compacted ballast layer, which quickly returns the track to its pre-maintenance position. Then, other maintenance techniques such as stoneblowing, as well as diverse solutions that reinforce trackbed, have been developed to reduce ballast settlement and particles degradation. Given the need to further advance research in this field, bitumen-stabilised ballast (BSB) has started to be investigated by the authors as a feasible solution thanks to its easy and quick appl…
Effect of temperature and traffic on mix-design of bituminous asphalt for railway sub-ballast layer
2017
A wide integrated research has been carried out to assess the suitability of bituminous mixtures as the sub-ballast layer in railways. The influence of temperature on the mechanical characteristics and thermal susceptibility of the bituminous conglomerate—which forms sub-ballast layer of railway lines—has provided the motivation for carrying out a measurement of the thermal cycles in this layer. The evaluation of the average seasonal temperatures has proven to be well interpolated by sinusoidal functions, of which characteristic parameters are determined. To expand the validity of the study in different weather situations apart from Sicily, where the experiment was held, we proceeded to app…
Stiffness and strength of composite truss beam to R.C. column connection in MRFs
2015
Abstract The results of experimental and numerical investigations on the cyclic behavior of composite truss beam to reinforced concrete column connection of moment resisting frames are reported. The beams are constituted by a steel truss and end zone added rebar embedded within a concrete block cast in place, so that, after curing, the steel truss and the added rebar work together with the concrete matrix as reinforcement of the composite beam. Particularly, three specimens of two-span continuous beams were tested under monotonic and cyclic actions as three point bending test. With the goal to investigate about the behavior of the end zone of the beam integrated into a moment resisting fram…
Efficacy of dulaglutide on vascular health indexes in subjects with type 2 diabetes: a randomized trial
2021
Abstract Background Recent cardiovascular outcome trials have shown significant reductions in major cardiovascular (CV) events with glucagon-like peptide (GLP)-1 receptor agonists. Additionally, adjunctive surrogates for cardiovascular risk validated by some studies include arterial stiffness and endothelial function indexes. To date, no randomized trial has addressed the possible effects of antidiabetic interventional drugs such as GLP1 agonists on endothelial and arterial stiffness indexes as surrogate markers of vascular damage. Aims We aimed to evaluate metabolic efficacy and surrogate vascular efficacy endpoints of once-weekly dulaglutide (1.5 mg) plus traditional antidiabetic treatmen…
Effect of two novel bio-based rejuvenators on the performance of 50% RAP mixes - a statistical study on the complex modulus of asphalt binders and as…
2019
An experimental study was conducted to evaluate the effectiveness of two bio-additives as rejuvenators on the properties of asphalt mixtures containing 50% RAP and their binder constituents containing 37% RAP binder. Before mixing, the rejuvenators were blended with fresh bitumen and the extracted and recovered RAP bitumen, and changes in the rheological properties of the binders were assessed using performance grading (PG) criteria. The results showed that both rejuvenators could improve the low-temperature performance of the aged RAP binder and restore its low-temperature properties. Master curves for the unaged, RTFO-aged, and PAV aged blends were constructed using both the Christensen-A…
Effect of stiffness on the phase behavior of cubic lattice chains
2005
Gran canonica Monte Carlo (GCMC) simulazioni assistite da tecniche di riponderazione istogramma sono stati utilizzati per studiare l'effetto della flessibilità catena sul comportamento di soluzione fase di cubi catene reticolari corti con 4-32 segmenti. Ciò è stato fatto variando un parametro di rigidità gradualmente fino alla media calcolata end-to-end distanza avvicinato la lunghezza totale. Per entrambe le catene flessibili e rigide si è riscontrato che la temperatura critica, ottenuta tramite mista analisi dei campi di dimensioni finite, aumentata lunghezza della catena e la densità critica trasferisce a valori più bassi, in accordo con le osservazioni sperimentali. Il estrapolato lungh…
Determining cantilever stiffness from thermal noise
2013
We critically discuss the extraction of intrinsic cantilever properties, namely eigenfrequency fn, quality factor Qn and specifically the stiffness kn of the nth cantilever oscillation mode from thermal noise by an analysis of the power spectral density of displacement fluctuations of the cantilever in contact with a thermal bath. The practical applicability of this approach is demonstrated for several cantilevers with eigenfrequencies ranging from 50 kHz to 2 MHz. As such an analysis requires a sophisticated spectral analysis, we introduce a new method to determine kn from a spectral analysis of the demodulated oscillation signal of the excited cantilever that can be performed in the frequ…
Scanning force microscopy based rapid force curve acquisition on supported lipid bilayers: experiments and simulations using pulsed force mode.
2004
In situ pulsed force mode scanning force microscopy (PFM-SFM) images of phase separated solid-supported lipid bilayers are discussed with the help of computer simulations. Simultaneous imaging of material properties and topography in a liquid environment by means of PFM-SFM is severely hampered by hydrodynamic damping of the cantilever. Stiffness and adhesion images of solid-supported membranes consisting of cholesterol, sphingomyelin, and 1,2-dioleyl-phosphatidylcholine obtained in aqueous solution exhibit contrast inversion of adhesion and stiff. ness images depending on parameters such as driving frequency, amplitude, and trigger setting. Simulations using a simple harmonic oscillator mo…