Linear and nonlinear viscoelastic and viscoplastic analysis of asphalt binders with warm mix asphalt additives

Warm-Mix Asphalt (WMA) is a widely used product, which proved a contribution to the reduction in asphalt mixing and compaction temperatures. This reduction leads to lower fuel consumption and smoke emission in asphalt plants. Most of the characterisation of binders used in WMA has focused in the past on measuring linear viscoelastic properties and associated Superpave parameters. Several studies have shown that the average stresses and strains of the asphalt mixture remain mostly within the linear viscoelastic response. However, localised strains in the binder phase of the mixture could reach values high enough to induce nonlinear viscoelastic and viscoplastic deformations. Therefore, this study focuses on an experimental and analytical evaluation of linear, nonlinear viscoelastic and viscoplastic responses of selected binders modified for use in WMA. The first part of the paper analyses the linear viscoelastic material properties and their ability to evaluate permanent deformation resistance. Then, the non-recoverable creep compliance parameter obtained from the Multiple Stress Creep Recovery (MSCR) test is analysed to assess the nonlinear response and permanent deformation of asphalt binders. The paper utilises a nonlinear plasto-viscoelastic (NPVE) approach to assess and quantify the nonlinear plasto-viscoelastic response of binders by separating the recoverable and irrecoverable strains measured in the MSCR test. Two WMA additives were included in this study by mixing them with polymer-modified and unmodified asphalt binders. Analysis of results showed that the NPVE approach captured a higher percentage of recovery than the NLVE approach. However, binder’s performance evaluation and ranking did not change by adopting the NPVE approach. The nonlinear viscoelastic parameters provided insight on the behaviour of asphalt binders mixed with WMA additives during loading cycles. Sasobit showed higher influence than Advera on binders in resisting permanent deformation by increasing the recoverable strain during the unloading phase.     

Effects of reactive and nonreactive POSS types on the mechanical,thermal, and morphological properties of plasticized poly(lactic acid)

The aim of this study is to investigate the effects of the reactive and nonreactive polyhedral oligomeric silsesquioxane (POSSs) types and their composition on the mechanical, thermal, and morphological properties of poly(ethylene glycol) plasticized poly(lactic acid) (PLA) composites prepared with melt compounding. The results showed that the incorporation of POSS decreased the melt viscosity of the compounds regardless of POSS type. The lowest viscosity was obtained with epoxy‐POSS, which is the only one that is liquid at processing temperature in comparison to the others. It was revealed from the mechanical tests that the toughness‐related properties such as impact strength and elongation at break improved by the addition of POSS without remarkable deterioration in stiffness. The chemical structure of the POSS influenced the level of dispersion and hence the mechanical performance of the composites. Octaisobutyl‐POSS, being the nonreactive and nonpolar one, had the best dispersion among the other reactive and polar POSS types. The glass transition temperature of the matrix decreased in the presence of POSS types. In addition, the POSS particles also had an impact on the crystallization of PLA. The thermal stability of the composites improved in the presence of POSS particles with respect to the POSS content and the POSS type. POLYM. ENG. SCI., 54:264–275, 2014. © 2013 Society of Plastics Engineers     

Resuspension of soil as a source of airborne lead near industrial facilities and highways

Geologic materials are an important source of airborne particulate matter less than 10 microm aerodynamic diameter (PM10), but the contribution of contaminated soil to concentrations of Pb and other trace elements in air has not been documented. To examine the potential significance of this mechanism, surface soil samples with a range of bulk soil Pb concentrations were obtained near five industrial facilities and along roadsides and were resuspended in a specially designed laboratory chamber. The concentration of Pb and other trace elements was measured in the bulk soil, in soil size fractions, and in PM10 generated during resuspension of soils and fractions. Average yields of PM10 from dry soils ranged from 0.169 to 0.869 mg of PM10/g of soil. Yields declined approximately linearly with increasing geometric mean particle size of the bulk soil. The resulting PM10 had average Pb concentrations as high as 2283 mg/kg for samples from a secondary Pb smelter. Pb was enriched in PM10 by 5.36-88.7 times as compared with uncontaminated California soils. Total production of PM10 bound Pb from the soil samples varied between 0.012 and 1.2 mg of Pb/kg of bulk soil. During a relatively large erosion event, a contaminated site might contribute approximately 300 ng/m3 of PM10-bound Pb to air. Contribution of soil from contaminated sites to airborne element balances thus deserves consideration when constructing receptor models for source apportionment or attempting to control airborne Pb emissions.     

On multimedia networks: self-similar traffic and networkperformance

The main objective in telecommunications network engineering is to have as many happy users as possible. In other words, the network engineer has to resolve the trade-off between capacity and QoS requirements. Accurate modeling of the offered traffic load is the first step in optimizing resource allocation algorithms such that provision of services complies with the QoS constraints while maintaining maximum capacity. As broadband multimedia services became popular, they necessitated new traffic models with self-similar characteristics. We present a survey of the self-similarity phenomenon observed in multimedia traffic and its implications on network performance. Our current research aims to fill the gap between this new traffic model and network engineering. An immediate consequence of this study is the demonstration of the limitations or validity of conventional resource allocation methods in the presence of self-similar traffic     

Evaluation of the effects of different remineralizing agents on Streptococcus mutans biofilm adhesion

The aim of the study was to compare the effects of different remineralization methods that are well established in clinical and daily use on S. mutans biofilm adhesion. In this study 72 human third molars were used. From each tooth two pieces of 4?mm x 7?mm enamel blocks were acquired. The samples were divided into 6 groups in which include 10 samples per time period (24h and 48?h) and for each remineralization method; control, flouride, ozone, CPP-ACP, arginine, novamin. After remineralization procedures, enamel surfaces were covered with saliva. 10⁵ CFU/mL of active S. mutans culture were inoculated onto the samples. S. mutans colonies were counted with Plate Count Agar (PCA) decimal dilution method. Micromorphologic effects of different remineralization methods were observed by Scanning Electron Microscopy (SEM). The most S. mutans biofilm formation for both time periods was observed in the control group whereas the less biofilm adhesion was showed in the arginine group. There were no statistically significant differences among remineralization agents (p?>?0.05). In the control group there was statistical difference between 24?h and 48?h (p?<?0.005) but in the other study groups there were no significant difference between the time periods (p?>?0.05). Remineralization agents did not significant differ on S. mutans biofilm adhesion.     

Swoop: A Web Ontology Editing Browser

In this paper, we describe Swoop, a hypermedia inspired Ontology Browser and Editor based on OWL, the recently standardized Web-oriented ontology language. After discussing the design rationale and architecture of Swoop, we focus mainly on its features, using illustrative examples to highlight its use. We demonstrate that with its Web-metaphor, adherence to OWL recommendations and key unique features, such as Collaborative Annotation using Annotea, Swoop acts as a useful and efficient Web Ontology development tool. We conclude with a list of future plans for Swoop, that should further increase its overall appeal and accessibility.     

When Teachers' and Parents' Values Differ: Teachers' Ratings of Academic Competence in Children From Low-Income Families.

The authors examined predictors of teachers' ratings of academic competence of 105 kindergarten children from low-income families. Teachers rated target children's expected competence in literacy and math and completed questions about their perceptions of congruence-dissonance between themselves and the child's parents regarding education-related values. Independent examiners assessed children's literacy and math skills. Teachers' instructional styles were observed and rated along dimensions of curriculum-centered and student-centered practices. Controlling for children's skills and socioeconomic status, teachers rated children as less competent when they perceived value differences with parents. These patterns were stronger for teachers who exhibited curriculum-centered, rather than student-centered, practices. The findings suggest a mechanism by which some children from low-income families enter a path of diminished expectations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reducing computation time of a wireless resource scheduler by exploiting temporal channel characteristics

Wireless Networks - The long term evolution downlink scheduler must attain a low computation time as it performs scheduling decisions every 1&nbsp;ms. 5G New Radio introduced mini-slots for the...     

Bond strength of repaired composite resins: surface treatments,adhesive systems,and composite type

The aim of the present study was to investigate the effects of three different surface treatments and two different adhesives on the microtensile bond strength (μTBS) of repaired composites using the same or different type of resin. Twenty-four nano-hybrid (Ceram X mono-C) and 24 nanofilled (Filtek Ultimate-F) composite discs were prepared. The specimens were aged with 5000 thermocycles and randomly divided into groups according to the surface treatment methods: (a) phosphoric acid (b) Er:YAG laser and (c) aluminum trioxide particle (air abrasion). Fresh composite resins (C and F) were added to the treated surfaces with two different adhesives (two-step and one-step self-etch adhesives). Then, the specimens were aged again. The stick-shaped specimens were prepared from the discs (n = 25) and the sticks were subjected to the μTBS test. Results indicated that significant differences were found in μTBS values among the surface treatment methods. In the C groups, the highest μTBS value (41.3 ± 8.3 MPa) was recorded in the air abrasion and one-step self-etch adhesive group, which were repaired with the same kind of composite. In the F groups, the highest μTBS value was observed in the air abrasion and one-step self-etch adhesive (37.6 ± 12.3 MPa) group. The treatment with air abrasion is more effective than the others, and it may be suggested for composite repair.     

Dephytinization of food stuffs by phytase of Geobacillus sp. TF16 immobilized in chitosan and calcium-alginate

In this work, Geobacillus sp. TF16 phytase was separately immobilized in chitosan and Ca-alginate with the efficiency of 38% and 42%, respectively. These enzymes exhibited broad substrate specificity. Maximal relative phytase activity was measured at pH 5.0 and 95°C and pH 3.0 and 75°C for chitosan and Ca-alginate, respectively. The enzymes were highly stable in a wide pH and temperature range. Values of K_m and V_max were determined as 2.38 mM and 3401.36 U/mg protein for chitosan, and 7.5 mM and 5011.12 U/mg protein for Ca-alginate. The immobilized enzymes showed higher resistance to proteolysis. After 4 h incubation, hydrolysis capacities of chitosan- and Ca-alginate immobilized enzymes for soymilk phytate were calculated as 24% and 33%, respectively. The chitosan- and Ca-alginate immobilized phytases conserved its original activity after 8 and 6 cycles of reuse, respectively. The features of the enzymes were very attractive and they might be useful for some industrial applications.