SP70-alpha-benzoin oxime chelating resin for preconcentration-separation of Pb(II), Cd(II), Co(II) and Cr(III) in environmental samples

In the presented work, alpha-benzoin oxime immobilized SP70 chelating resin was synthesized for separation and preconcentration of Pb(II), Cd(II), Co(II) and Cr(III). The optimization procedure for analytical parameters including pH, eluent type, flow rate, etc. was examined in order to gain quantitative recoveries of analyte ions. The effects of foreign ions on the recoveries of studied metal ions were also investigated. The detection limits (3sigma) were found to be 16.0, 4.2, 1.3, 2.4microgL(-1) for Pb, Cd, Co and Cr, respectively. The preconcentration factor was 75 for Pb, 100 for Cd, Co and Cr. The optimized method was validated with certified reference materials and successfully applied to the waters, crops and pharmaceutical samples with good results (recoveries greater than 95%, R.S.D. lower than 10%).     

An iterated beam search algorithm for the multi-level production smoothing problem with workload smoothing goal

This paper is concerned with a generalised version of the production smoothing problem. The problem involves both usage and loading goals at multiple levels. Three existing heuristic approaches, namely the one-stage (1SH), two-stage (2SH) and earliest-due-date (EDD) heuristics are adapted, as well as a novel iterated beam search (IBS) algorithm is proposed to solve the problem. An extensive computational study is designed in the paper and used to compare the four heuristic approaches. The results show that IBS finds the best solution in the majority of test instances and requires less computation time than 2SH.     

Analysis and solution to the single-level batch production smoothing problem

Many companies use mixed-model production systems running under the Just-in-Time philosophy in order to efficiently meet customer demands for a variety of products. Such systems require demand be stable and production sequence be leveled. The production smoothing problem aims at finding level schedules in which the appearances of products are dispersed over the horizon as uniformly as possible. In this paper, the production smoothing problem is extended to a more general manufacturing environment where a single machine can be identified as either the final or the bottleneck stage of the system and products may have arbitrary non-zero setup and processing time requirements on this single machine. An optimization model is built for the problem and a two phase solution methodology is developed. The first phase problem is shown to be NP-hard and a parametric heuristic procedure is proposed for its solution. In contrast, the second phase problem is shown to be efficiently solvable and currently available solution methods are adopted from the literature. A computational study is designed to test the proposed two phase solution methodology and also the parametric heuristic procedure. Computational results show that the proposed two phase solution methodology enables effective and efficient control of the studied manufacturing system, and the heuristic procedure developed for the first phase problem is time efficient and promises near optimal solutions for a variety of test instances.     

Dynamic mechanical behavior of some carbonate rocks

The effects of porosity, unit volume weight and Schmidt hardness on the quasi-static and dynamic compressive behaviors of some carbonate rocks were investigated using classical servo-hydraulic testing machine and split Hopkinson pressure bar (SHPB) testing system, respectively. For dynamic compression testing, cylindrical samples 18 mm in diameter and 11 mm long were obtained from rock samples of light and dark travertines, lymra and beige marbles. For quasi-static compression testing, cylindrical samples were prepared according to the International Society for Rock Mechanics (ISRM) standards. The results of the physical and mechanical properties of the rock samples have shown that the porosity, unit volume weight and Schmidt hardness, have significant effects on the compressive stress–strain behavior of the rock samples under dynamic loading. The results have also shown that the beige limestone samples have significantly higher dynamic compressive strength than the other carbonate rock samples.     

Preparation of poly(acrylamide) grafted onto crosslinked poly (HEMA-MMA-EGDMA) beads for the removal of phenol

ABSTRACT

Poly(acrylamide) (PAAM) was grafted onto crosslinked poly(hydroxy ethyl methacrylate) (HEMA)-based beads for the removal of phenol from aqueous solution. A beaded polymer with a PAAM surface shell was prepared in two steps: synthesis of crosslinked poly (HEMA (50% mol) - MMA (40% mol) - EGDMA (10% mol)) terpolymers spherical beads (200–420 µm) (resin 1) via the suspension polymerization method; and the grafting of PAAM was carried out by redox initiation from hydroxyl groups on resin1 by using cerium (IV) ammonium nitrate as the initiator.

The resulting polymeric sorbent (resin 2) with about 82 wt.% grafted PAAM has been demonstrated to be efficient to remove phenol from water. Moreover, phenol sorption capacities of resin 1 and resin 2 were compared and sorption experiments were performed depending on the initial phenol concentration and pH. Kinetic measurements and models were studied for resin 1 and resin 2.     

Investigation of the Reaction Kinetics of Poly(butylene terephthalate) and Epoxide Chain Extender

Polyesters, such as poly (butylene terephthalate) (PBT), owe a rather low melt strength, which is considered as not beneficial for foaming. To overcome this issue, a typical attempt is the incorporation of chemical modifications—so-called chain extenders (CE)—in the reactive extrusion process. In this study, the reaction kinetic variables are investigated depending on the material and process parameters. For this purpose, different series of experiments are performed with varying PBT with different molecular weights and the commonly used CE, Joncryl ADR4468, on a micro compounder. The screw force is recorded and analyzed using an Avrami and an Arrhenius plot. First, the amount of CE is systematically varied. To study the course of the reaction in more detail, the reaction is stopped in a series of measurements (10, 30, 60, and 90 s after complete filling). Gel permeation chromatography (GPC), Fourier transform infrared spectroscopy (FT-IR), and Raman spectra are recorded. In the second series, the effect of processing temperatures between 250 and 270 °C is investigated, and finally, in the third series, the average molecular weight of PBT is varied. It could be shown that the activation energy seems to be dependent on the initial molecular weight; lower molecular weights result in lower activation energy.     

Push-out bonding strengths of four different dowel systems luted with two different adhesive systems

This in vitro study investigates the bonding capacity of resin cements to dowels, using the push-out bonding strength of four different dowel systems, namely, stainless steel dowels (SSD), resin-supported polyethylene fiber dowels (RSPFD), zirconia dowels (ZD), and superpost glass fiber dowels (GFD), luted in root canals, using two different resin cements, namely, Multilink Automix Cement and Clearfil Esthetic Cement. Ninety-six maxillary central incisor teeth were sectioned below the cementoenamel junction, and the roots were treated endodontically. Then the roots were placed into four groups, based on the dowel systems used. The roots were further placed into two subgroups, based on the cement type used as subgroup A and subgroup B. Push-out bonding tests were performed on the bonded specimens, which were cut into 1 mm thick sections. A two-way ANOVA test and Tukey’s HSD tests were performed. The push-out bonding strength values for SSD, ZD, and RSPFD were not significantly different (p > 0.05). The means for GFD were significantly higher than the means for ZD (p < 0.05) when Multilink Automix Cement was used. However, when Clearfil Esthetic Cement was used, the means for RSPFD were significantly higher (p < 0.001) than the means for the other systems. When Clearfil Esthetic Cement was used, the RSPF dowel system provided significantly higher bonding strength values than the other systems.     

A typical application of magnetic field inwastewater treatment with fluidized bed biofilm reactor

The effects of a magnetic field on wastewater treatment with a fluidized bed biofilm reactor was investigated. With glucose being the sole carbon source, the activated sludge obtained from a real wastewater treatment plant was used as a seed. Magnetically loaded polystyrene beads at the size of 500-595 w m were used as support materials for biofilm formation in a fluidized bed biofilm reactor. Magnetic field application allowed the operation of the column at high liquid flow rates, thus external diffusion limitations on the biofilm surface were lowered and the efficiency of biodegradation was increased. Denser, thinner, and more active biofilm was obtained with magnetic field application, especially in pulsed form. As expected, the system performance changed with operational parameters, and the increase in substrate removal reached up to 26% with pulsed application of a 17.8 mT DC-magnetic field under optimum conditions.