Search results for "Forced"

Durability of Basalt/Hemp Hybrid Thermoplastic Composites

2019

The Achilles heel of thermoplastic natural fibre composites is their limited durability. The environmental degradation of the mechanical properties of hemp and hemp/basalt hybrid-reinforced high-density polyethylene (HDPE) composites has been investigated with a special focus on the effects of water ageing and accelerated ageing, including hygrothermal and UV radiation. Modification of the matrix was carried out using a maleic anhydride high-density polyethylene copolymer (MAPE) as a compatibilizer. Hybridization of hemp fibres with basalt fibres and the incorporation of MAPE were found to significantly decrease the water uptake (up to 75%) and increase the retention of mechanical propertie…

1997

We have determined by forced Rayleigh scattering the diffusion coefficients of photo-labeled polystyrene micronetwork spheres (radii ≤ 10 nm) in melts of linear polyvinylmethylether (M W ≤ 40000 g/mol) at temperatures of 20-80°C. An expected slippage of the spheres through the meshes of the entanglement network appears possible but is still within the experimental uncertainty of our results.

Probing Poly(n-butyl-methacrylate) Latex Film via Diffusion of Hydrophilic and Hydrophobic Dye Molecules

2003

In the study of holographic grating relaxation (forced Rayleigh scattering, FRS) in nascent latex films we examined poly(n-butyl methacrylate) films using two complementary diffusing probes:  a hyd...

A study of spalling behaviour of PAN fibre-reinforced concrete by thermal analysis

1993

Comparisons are made between polypropylene (PP) fibres and polyacrylonitrile (PAN) fibres in order to relate the thermal properties of fibres with the respective fibre mortar behaviour under thermal exposure. Thermogravimetry (TG), differential scanning calorimetry (DSC) and thermochromatography (ThGC) are utilized. When a cementitious fibre mortar is being heated, several physical phenomena occur in the temperature range between 100°C and 200°C. There is a significant difference in the thermal behaviour between PP and PAN fibres. PP fibres melt at 160–170°C. The non‐melting behaviour of PAN fibre together with its rapid exothermic degradation reactions at around 300°C may add risk to the s…

Vivir como cristianos y pagar como moros: genealogía medieval de la servidumbre morisca en el reino de Valencia

2009

La conversión forzosa de los musulmanes del reino de Valencia, decretada en 1526, no implicó una igualación social entre cristianos «viejos» y «nuevos», ya que se mantuvo la diferencia de estatus que había existido anteriormente. El artículo examina los tres aspectos fundamentales del contenido de dicha diferencia: la intensidad de las rentas soportadas, la imposición de servicios obligatorios y las trabas a la migración interior y exterior; establece sus orígenes en las condiciones de dominación impuestas a la población infiel inmediatamente después de la conquista del siglo XIII, y traza los grandes rasgos de su evolución a lo largo de la Baja Edad Media. Se arguye que esta población estu…

Performance of a historical cantilever reinforced concrete bridge with half-joint degradation

2022

The lack of maintenance of roadway concrete bridges built from the Second World War until the 70 s of the 20th century has led in recent years to an ever-increasing request for safety assessments. When bridge performance in terms of Serviceability Limit State (SLS) and Ultimate Limit State (ULS) has to be evaluated, in-situ visual inspections and load tests for safety and maintenance assessment have to be coupled with structural analysis. In order to identify a sound bridge structural model and to assess the actual conservation state, more refined models than those usually considered for section and reinforcement design should be used to reproduce the results of load tests and perform globa…

Small-sample characterization of stochastic approximation staircases in forced-choice adaptive threshold estimation

2007

Despite the widespread use of up—down staircases in adaptive threshold estimation, their efficiency and usability in forced-choice experiments has been recently debated. In this study, simulation techniques were used to determine the small-sample convergence properties of stochastic approximation (SA) staircases as a function of several experimental parameters. We found that satisfying some general requirements (use of the accelerated SA algorithm, clear suprathreshold initial stimulus intensity, large initial step size) the convergence was accurate independently of the spread of the underlying psychometric function. SA staircases were also reliable for targeting percent-correct levels far …

Effect of cigarette smoking on airway responsiveness to adenosine 5'-monophosphate in subjects with allergic rhinitis.

2003

Study objectives: The objective of this study was to determine differences in airway responsiveness to adenosine 5-monophosphate (AMP) between smokers and nonsmokers with allergic rhinitis. Methods: A total of 41 adults with allergic rhinitis (16 smokers and 25 nonsmokers) were challenged with increasing concentrations of methacholine and AMP. Airflow was assessed after each concentration, and the response to each bronchoconstrictor agent was measured by the provocative concentration required to produce a 20% fall in FEV1 (PC20). Results: The geometric mean PC20 AMP values were significantly lower in smokers than in nonsmokers: 72.4 mg/mL (95% confidence interval [CI], 33.9 to 154.9) vs 204…

Relationship between airway sensitivity to adenosine 5' monophosphate and the shape of the concentration-response curve to methacholine in subjects w…

2001

Abstract The objective of this study was to determine differences in airway sensitivity to adenosine 5′-monophosphate (AMP) between allergic rhinitis subjects with plateau and those without evidence of plateau on the concentration–response curves to methacholine. A total of 51 adults (38 subjects with allergic rhinitis and 13 healthy controls) were challenged with increasing concentrations of methacholine and AMP. The methacholine challenge was terminated when there was a 40% or more decrease in forced expiratory volume in 1 sec (FEV 1 ), whereas the AMP challenge was stopped when FEV 1 had fallen by more than 20%. A plateau for methacholine was detected in all 13 healthy controls and in 27…

Effect throughout the day of inhaled fenoterol on the bronchial responsiveness to histamine in asthmatic patients.

1987

The effect throughout the day of inhaled fenoterol on the bronchial responsiveness to inhaled histamine was evaluated in 8 asthmatic patients. The airway response to increasing concentration of histamine aerosol was assessed by measurement of forced expiratory volume in one second (FEV1). The provocative dose of histamine needed to cause a 20% fall in starting FEV1 was calculated from the cumulative log dose response curves. Histamine challenges were performed in duplicate, on separate days, after premedication with placebo or fenoterol given by metered dose inhalers in the morning and in the afternoon. The mean starting FEV1 in the morning and in the afternoon did not change significantly …