Contractor-Performed Quality Control: Is the Fox Guarding the Henhouse?

At the same time that state departments of transportation are allowing contractor-performed quality control, they are also concerned about using the contractor-reported data for acceptance and payment purposes. The question is, are we putting the fox in charge of guarding the chickens? To address this concern, a large number of asphalt and concrete projects in Kentucky were examined. The statistical analyses showed that for the most part there is no significant difference between the contractor-performed acceptance data and concomitant highway agency-performed verification data. This is obviously a very encouraging finding that is expected to enhance the level of trust between the contractors and highway agencies.     

The Discontinuous Galerkin Method for Two-Dimensional Hyperbolic Problems. Part I: Superconvergence Error Analysis

In this paper we investigate the superconvergence properties of the discontinuous Galerkin method applied to scalar first-order hyperbolic partial differential equations on triangular meshes. We show that the discontinuous finite element solution is O(h ^p+2) superconvergent at the Legendre points on the outflow edge for triangles having one outflow edge. For triangles having two outflow edges the finite element error is O(h ^p+2) superconvergent at the end points of the inflow edge. Several numerical simulations are performed to validate the theory. In Part II of this work we explicitly write down a basis for the leading term of the error and construct asymptotically correct a posteriori error estimates by solving local hyperbolic problems with no boundary conditions on more general meshes.     

Effect of the angle of attack on the wind convection coefficient

In this study the effect of the positive angle of attack (angle between flat plate surface and incoming uniform flow) on the convective heat transfer coefficient was investigated numerically. In the case of inviscid flow, this effect was also presented analytically and was found to be in good agreement with the corresponding numerical results. From the obtained numerical data, an accurate correlation equation of Nusselt number was proposed by introducing the effect of the angle of attack in terms of a new factor A_f. The variation of the convective heat transfer coefficient as a function of the angle of attack was found not behaves in the same manner for both small and large values of Prandtl number at small angles of attack.     

Investigations of High Temperature Wear Mechanisms for Tool Steel Under Open-Sliding Contact

During hot working processes, working tools are subjected to severe conditions. Wear is one of the major life limiting factors of the hot working tools. The identification and understanding of the wear mechanism are extremely important for solving problems related to the hot working process. The ultimate aim of this paper is to assess some wear mechanisms of the tool steel used in hot drawing. The tribological tests were performed on high temperature pin-on-disc tribometer with an open-sliding contact for a simulation of hot-drawing process with a refreshed contact surface. The pin material was X40 CrMoV5 steel and the disc material was Fe 360B steel. Experiments were carried out for different disc temperatures ranging from room temperature to 800°C, a constant sliding speed of 50 rev/min and a constant normal load of 70 N. The evolution surface damage and oxides tribolayers have been investigated by SEM and EDS. The results have shown that an increase in test temperature facilitates the generation of oxide and assists in the compaction of the debris, thus producing a wear protective layer, and therefore, a reduction in friction coefficient.     

Discontinuous Galerkin error estimation for hyperbolic problems on unstructured triangular meshes

We extend the error analysis of Adjerid and Baccouch [1], [2] for the discontinuous Galerkin discretization error to variable-coefficient linear hyperbolic problems as well as nonlinear hyperbolic problems on unstructured meshes. We further extend this analysis to transient hyperbolic problems and prove that the local superconvergence results presented in [1] still hold for both steady and transient variable-coefficient linear and nonlinear problems. This local error analysis allows us to construct asymptotically correct a posteriori error estimates by solving local hyperbolic problems with no boundary conditions on each element of general unstructured meshes. We illustrate the superconvergence and the efficiency of our a posteriori error estimates by showing computational results for several linear and nonlinear numerical examples.     

Effect of recycling and injection parameters on gloss properties of smooth colored polypropylene parts: Contribution of surface and skin layer

The aim of this article is to investigate the optical properties of a recycled polymer during numerous processes. The effects of different process parameters (number of grinding‐injection cycles, material temperature, mold temperature, and injection rate) on gloss and color properties of a buff‐colored polypropylene containing 2wt%/wt of pigment was considered. The variations of properties are in the same range that is observed by changing processing parameters. It is found that the roughness is not able to explicate the variation of the optical properties for these variations of conditions. In addition, the optical properties of the skin layer of the injected parts are associated with the observed gloss and color variations. Moreover, the change of spherulite dimensions is related with optical changes. POLYM. ENG. SCI., 59:1288–1299 2019. © 2019 Society of Plastics Engineers     

A study of the suitability of the KENTORT II eastern shale oil for asphalt paving applications

The uncertain future of petroleum reserves has fuelled the search for alternative resources. A feasibility study was conducted to determine potential paving applications of the oil extracted from eastern shale by the KENTORT II process. The eastern shale oil (ESO) in this study was separated into two drastically different viscosity portions, designated as ‘hard’ and ‘soft’ ESO. It was hypothesized that the ‘hard’ portion might enhance the asphalt performance by increasing the stiffness. It was discovered that the ‘hard’ ESO modified asphalt properties deteriorate significantly with time. On the other hand, the ‘soft’ ESO was found to exhibit desirable properties in an asphalt recycling application. Further studies are recommended to fully characterize the binder and mixture properties of ESO modified/rejuvenated asphalts.     

Preparation,characterization and evaluation of the catalytic power of an hybrid compound [H3PMo12O40-chitosan] for the azoic-colored solutions

Inorganic–organic hybrid structures have become novel alternatives for many applications as they combine the advantages of both systems. In this current study, a hybrid compound [H₃PMo₁₂O₄₀-chitosan] was prepared using a wet impregnation method with different proportions (0-100 wt. %, considering the polymer as the main component). The chemical structure and the morphology of the synthesized compounds were studied using FT-IR and SEM. Their catalytic powers were evaluated for Naphtol Blue Black and Eriochrome Blue Black B. Experimental data revealed that the decolorization phenomenon depends on the structure of the dye it-self, the pH value, the initial dye concentration, the time contact, the oxidant dose and the temperature. Kinetic data, well described using the first order model, allowed us to establish the thermodynamic parameters. The calculated low values of Ea (7.48 and 8.14 KJ. mol-1) proved the efficiency of the prepared catalyst. Eriochrome Blue Black B could be decomposed more rapidly than Naphtol Blue Black. As example, after a period of 30 min of reaction, the target removals were, respectively, 70% and 15% for mono and bi-azoic dyes. The reuse of the catalyst is carried out and it was found to be recyclable more than three consecutives cycles.