Experimental and MD simulation study on the physical and mechanical properties of organically modified montmorillonite clay and compatibilized linear low density polyethylene nanocomposites

Understanding the interfacial interactions plays a key role in controlling mechanical and physical properties of polymer/clay nanocomposites (PCNs). In this work, the surface interactions between constituents of experimentally prepared PCNs which are the pristine linear low density polyethylene (PE) chains, PE compatibilizers, montmorillonite clay surface layer, and surfactants were studied quantitatively by employing molecular dynamics simulation technique. The interaction energy between the polymer and the clay was found to be inversely proportional with the volume of the surfactant which decreases the electrostatic interactions between the compatibilizer and the hydrophilic clay surface. However, the van der Waals (vdW) interactions between alkyl tails of surfactants and the PE chains increase with the tail length of the surfactants. The most attractive interaction was between the surfactant's head group and the clay surface. We showed that there existed fine balance between the electrostatic and vdW type forces on the stability and the enhanced properties of the PE–organoclay nanocomposites. Calculated interaction energies were then correlated to the experimentally measured mechanical properties. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45817.     

Macro-azo-initiators having poly(ethylene glycol) units: Synthesis,characterization, and application to AB block copolymerization

Macro-azo-initiators (MAIs) having poly(ethylene glycol) (PEG) units were obtained by various multistep synthetic approaches. In the first stage, macro-azo-initiators of PEG type with azo groups inserted in the main chain were prepared. MAIs were then characterized by chemical analyses, spectral methods, ¹H-NMR, GPC, and DSC techniques. They were used in the free-radical bulk polymerization of dicyclohexylitaconate to synthesize AB block copolymers of poly(ethylene glycol-b-dicyclohexylitaconate) (PEG-b-PDCHI). © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65: 2173–2181, 1997     

Synthesis and characterization of poly(N‐isopropylacrylamide)s initiated with siloxane oligomer–(NH4)2Ce(NO3)6 redox pair

Poly(N‐isopropylacrylamide)s (PNIPAAM)s were synthesized via free‐radical polymerization using a ceric ammonium nitrate, Ce(IV)–α‐ω‐dihydroxy(polydimethylsiloxane) (Tegomer H‐Si 2111, PDMS) redox pair in hexane at 30°C in a nitrogen atmosphere. The dependence of the initiation and termination steps on the [NIPAAM]/[Ce(IV)] and [NIPAAM]/[PDMS] ratios were studied using gravimetry and FTIR, ¹H‐NMR, UV‐vis, and GFAA spectroscopy techniques. Gravimetric results indicated that, in the case of high concentrations of PDMS, the percentage of the solid portions of the products decreased while the amount of the oligomeric NIPAAM chains increased, that is, as the amount of PDMS in hexane was increased, the number of the short NIPAAM chains having PDMS segments at the two ends, also increased. UV‐vis results showed that the LCST of PNIPAAM initiated with Ce(IV) alone was higher than those of the ones that were synthesized using common initiator systems such as an ammonium persulfate–N,N,N′,N′‐tetramethylethylenediamine redox pair and azobis(isobutyronitrile). Further, it was observed that both siloxane blocks and ? NH? groups forming coordination bonds with free Ce(IV) ions and/or metal–ligand complexes had an important effect on the aggregation process of the chains. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1248–1254, 2003     

QoS‐aware LTE‐A downlink scheduling algorithm: A case study on edge users

4G/LTE‐A (Long‐Term Evolution—Advanced) is the state of the art wireless mobile broadband technology. It allows users to take advantage of high Internet speeds. It makes use of the OFDM technology to offer high speed and provides the system resources both in time and frequency domain. A scheduling algorithm running on the base station holds the allocation of these resources. In this paper, we investigate the performance of existing downlink scheduling algorithms in two ways. First, we look at the performance of the algorithms in terms of throughput and fairness metrics. Second, we suggest a new QoS‐aware fairness criterion, which accepts that the system is fair if it can provide the users with the network traffic speeds that they demand and evaluate the performance of the algorithms according to this metric. We also propose a new QoS‐aware downlink scheduling algorithm (QuAS) according to these two metrics, which increases the QoS‐fairness and overall throughput of the edge users without causing a significant degradation in overall system throughput when compared with other schedulers in the literature.     

A new sure-success generalization of Grover iteration and its application to weight decision problem of Boolean functions

In two recent papers, a sure-success version of the Grover iteration has been applied to solve the weight decision problem of a Boolean function and it is shown that it is quadratically faster than any classical algorithm (Braunstein et al. in J Phys A Math Theor 40:8441, 2007; Choi and Braunstein in Quantum Inf Process 10:177, 2011). In this paper, a new approach is proposed to generalize the Grover’s iteration so that it becomes exact and its application to the same problem is studied. The regime where a small number of iterations is applied is the main focus of this work. This task is accomplished by presenting the conditions on the decidability of the weights where the decidability problem is reduced to a system of algebraic equations of a single variable. Thus, it becomes easier to decide on distinguishability by solving these equations analytically and, if not possible, numerically. In addition, it is observed that the number of iterations scale as the square root of the iteration number of the corresponding classical probabilistic algorithms.     

Prediction of mechanical and physical properties of some sedimentary rocks from ultrasonic velocities

In this study, density, porosity, void ratio, and ultrasonic P- and S-wave first arrival times were measured on limestone, sandstone, and siltstone samples obtained by using mechanical soundings in the city of Zonguldak. Turkey. Fracture and fissure indexes of rocks were calculated from ultrasonic P- (Vp) and S-wave (Vs) velocities. Multi-parameter relationships occurred between ultrasonic velocities with seismic fracture and fissure indexes and physical and mechanical properties of the rocks. Root mean squared error (RMSE = 0.5–0.8%) values correlated between measured densities and densities calculated from Vp and Vs. The correlation coefficients of experimental relations between densities, void ratio, and porosity with seismic velocities that were obtained ranged from 78, 86, 67, and 84%, respectively. Consequently, natural, water-saturated and grain densities, porosity, and void ratio values were determined from new multi-parameter relationships obtained from the combined use of Vp and Vs. In addition, the results of this study suggest that the rock quality may wrongly be determined using the only Vp, whereas it can be obtained more accurately by using Vp and Vs together. The reason for this is that the P wave spreads in solid, liquid, and gas media, while the S-wave spreads only in solid media. Therefore, S-waves will not be altered by fracture filling (gas or liquid), while P-waves are affected by fracture filling. In the present study, the use of Vp and Vs together in relationships was more useful in determining the strength and hydraulic properties of rock mass that the use of either Vp or Vs alone. Also, Rock Quality Designation (RQD) and Rock Mass Rating (RMR) values can be correctly calculated from the combined use of Vp and Vs. As a result, interpretation of crack fill and classification of the rocks can be quickly performed using seismic velocities.

     

Structural modification of expandable polystyrene. I. Copolymerization with α‐methylstyrene

Conventional expandable polystyrene (EPS) was modified by the preparation of copolymers containing 1.0, 2.5, and 5.0% α‐methylstyrene. Increasing the glass‐transition temperature of EPS was the aim of this work. Copolymeric expandable polystyrene (CEPS) samples were characterized with various techniques. ¹H‐NMR spectroscopy was used for the determination of the composition, and gel permeation chromatography was used for the determination of the molecular weights and molecular weight distributions. Differential scanning calorimetry showed that the glass‐transition temperatures of the CEPS samples increased with increasing α‐methylstyrene contents. The prevention of the collapse of the EPS cells was observed in scanning electron microscopy images of the inner portions and outer surfaces of the CEPS samples. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 609–614, 2003     

Effects of fiber types and blend ratios on Murata Vortex yarn properties

Murata Vortex spinning (MVS) system is one of the unconventional systems for yarn manufacturing. It is suitable for spinning of 100% cotton fibers, synthetic fibers, and cotton/synthetic fiber blends which are 1 inch or more in length. The production ranges are between Ne 15-60. Vortex yarn and fabrics have low hairiness, clear appearance, high resistance to pilling and abrasion. In this study, the vortex yarns with Ne 30 are produced in different blend ratios in Murata Vortex Spinner using carded cotton, viscose, modal, silver-added polyester (Flexsil-D2?), polyester, and nylon 6.6 fibers. Vortex spun yarns are tested to determine the yarn properties which are diameter, density, roundness (shape), unevenness, imperfection, Uster hairiness (H), Zweigle hairiness, tenacity, and elongation. The study reveals that the fiber type has quite significant effects on yarn properties. In terms of structural properties, cotton is the most negative fiber while regenerated cellulosic fibers are the most positive. As modal, nylon and polyester fiber increase yarn strength, nylon and viscose fiber increase breaking elongation. Viscose and modal reduce unevenness, imperfection and hairiness while polyester and nylon exhibit more negative effect on these properties.     

Effects of drying process on antioxidant activity of purple carrots

Purple carrot was analysed for its antioxidant activity by measuring its scavenging effect on 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical. The amount of purple carrot necessary to decrease by 50% the initial DPPH concentration (EC50) was found 30.23 +/- 5.17 (mg sample/mg DPPH). Effects of the dehydration process on the antioxidant activity of purple carrots were also determined after dehydration by using tray drier and microwave+tray drier combination. Purple carrots were cleaned, washed, sorted, sliced, and blanched in water at 98 +/- 1 degree C for 2 min. Then half of the samples were dehydrated in microwave (45 min) and tray drier (105 min) combination, and others were dehydrated in tray drier (150 min) until reaching the constant weight. Raw, blanched and dehydrated purple carrots were compared for their antioxidant activity and total anthocyanin contents, color values (L*, a*, b*, C*, H degrees) and dry matter contents. The antioxidant activity as measured by DPPH, EC50 value ranged from 7.80 to 30.23 of processed and raw carrots where the H degrees values were changed from -3.68 to -23.96 corresponding to a bluish hue.