61 research outputs found
Dynamics of accommodative fatigue in rhesus monkeys and humans
AbstractChanges in accommodative dynamics with repeated accommodation were studied in three anesthetized rhesus monkeys and two conscious humans. Maximum accommodation was centrally stimulated via the Edinger–Westphal nucleus in monkeys with a 4 s on, 4 s off paradigm (4×4) for 17 min, 4×1.5 for 27 min and 2×1 for 16 min. Humans accommodated repeatedly to visual targets (5×5; 5D and 2×2; 6D) for 30 min. In all cases, accommodation was sustained throughout. The anesthetized monkeys showed inter-individual variability in the extent of changes in accommodative dynamics over time while no systematic changes were detected in the human accommodative responses. Little accommodative fatigue was found compared to previous studies which have reported a complete loss of accommodation after 5 min of repeated stimulation in monkeys
Initial smoothness of concrete pavements under environmental loads
In the current paper, the effect of curling and warping, caused by environmental ambient conditions, on the initial smoothness of concrete pavements is discussed. Surface profile measurements were made during the hours of the early morning and late afternoon on an instrumented jointed plain concrete pavement (JPCP) on highway US-30 near Marshalltown, Iowa during the first seven days after construction in summer 2005. Variations in temperature and moisture during this critical period were monitored using the temperature and relative humidity sensors installed within the test sections at the time of construction. Based on the measured surface profile data, it was observed that the initial pavement smoothness, in terms of international roughness index (IRI) and the ride number (RN), was not significantly influenced by the early-age curling and warping behaviour of the JPCP. Using finite-element modelling (FEM), sensitivity studies were conducted to investigate the influence of slab curvature on initial pavement smoothness for a range of equivalent temperature differences between the top and bottom of the slab. The results indicated that the initial JPCP smoothness is sensitive to changes in slab curvature resulting from environmental ambient conditions only at higher magnitudes. Although the FEM-based IRI predictions were higher than the surface profile-based IRI values, the differences were not significant
Electron emission in ionization of He and Ne by fast dressed oxygen ions and projectile-charge-state dependence
The double-differential cross sections (DDCS) of low-energy electrons emitted at forward, backward, and perpendicular directions are reported for collisions of 3.75 MeV/u Oq+ (q=5, 6, 7, 8) projectiles with He and Ne targets. The measured DDCS are found to be deviating from the q2 dependence throughout the entire energy region. The effect of projectile electrons, for the dressed ions, as a function of the impact parameter is clearly noticeable for large as well as low-impact parameter collisions. We also present a theoretical calculation based on the prior form of the continuum distorted wave-eikonal initial state approximation, in which the projectile-active electron interaction is modeled with the Green-Sellin-Zachor potential. This particular representation of the potential has been proven to give good qualitative results for projectiles with residual electrons. In addition to the total DDCS, the individual contributions from target ionization, projectile electron loss, and simultaneous ionization processes are also calculated. The total DDCS obtained from these calculations are shown to be in excellent agreement with the experimental observations.Fil: Biswas, Shubhadeep. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Kasthurirangan, S.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; España. Institute of Chemical Technology; IndiaFil: Misra, D.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; EspañaFil: Monti, Juan Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Rivarola, Roberto Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Física de Rosario. Universidad Nacional de Rosario. Instituto de Física de Rosario; ArgentinaFil: Fainstein, Pablo Daniel. Comisión Nacional de Energía Atómica. Centro Atómico Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Tribedi, L.C.. International Centre Of Theoretical Science. Tata Institute Of Fundamental Research; Españ
Impact ionization of molecular oxygen by 3.5-MeV/u bare carbon ions
We have measured the absolute double-differential cross sections (DDCSs) for electron emission in ionization of O2 molecules under the impact of 3.5-MeV/u C6+ ions. The data were collected between 10 and 600 eV, in an angular range of 30◦ to 150◦. The single-differential cross sections (SDCSs) in emission angle and electron energy are deduced from the electron DDCS spectra. Also, the total cross section has been obtained from the SDCS spectra. The DDCS spectra as well as the SDCS spectra are compared with continuum distorted-wave eikonal initial-state calculations which employ molecular wave functions built as linear combinations of atomic orbitals. The DDCS ratio i.e. σO2/2σO, derived by dividing the experimental DDCS for molecular oxygen with the theoretical DDCS for atomic oxygen, does not show any primary or secondary oscillations arising from Young-type interference, which is apparently in contrast to what has been observed earlier for H2 and in agreement with the model calculation. Similarly, the forward-backward angular asymmetry increases monotonically with the velocity of the emitted electrons. However, the results on the DDCSs, SDCSs, the asymmetry parameter, and the nonexistence of oscillations are in qualitative agreement with the predictions of the model usedOne of the authors (F.M.) acknowledges the financial support from the MICINN Projects No. FIS2010-15127 and No. CSD 2007- 00010. C.A.T., R.D.R., and F.M. acknowledge the Programa de Cooperación Interuniversitaria e Investigación Científica entre España e Iberoamérica AECID Project No. A2/039631/1
Integrated stochastic life cycle benefit cost analysis of hydronically-heated apron pavement system
Transportation infrastructure is greatly impacted by ice and snow, adding enormous costs to the American economy. Because of their sustainability benefits, heated-pavement systems (HPS) continue to gain attention as a potential alternative to conventional snow removal operations, and the main goal of this paper is to assess the economic feasibility of hydronically-heated pavements systems (HHPS), one type of heated pavements, for use at apron areas of commercial airports. Both benefits and expenses associated with use of HHPS for snow and ice removal were identified and quantified in monetary terms using a stochastic economic analysis method, and a sensitivity analysis approach was used to determine particular variables that significantly influence overall economic viability of HHPS. The findings suggest that, despite high capital costs, HHPS use at airports might be economically feasible. The results from the sensitivity analysis indicate that airport size, in the context of number of aircraft operations, strongly affects the benefit-cost ratio of HHPS use
Moisture Susceptibility of Subgrade Soils Stabilized by Lignin-Based Renewable Energy Coproduct
HIGHWAY INFRASTRUCTURE HEALTH MONITORING USING MICRO-ELECTROMECHANICAL SENSORS AND SYSTEMS (MEMS)
Airfield pavement deterioration assessment using stress-dependent neural network models
Neural Networks Modeling of Stress Growth in Asphalt Overlays due to Load and Thermal Effects during Reflection Cracking
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