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Reactive Compatibilization of Ethylene-co-Vinyl Acetate/Starch Blends
Piming Ma,Denka Georgieva Hristova-Bogaerds,Pauline Schmit,Johannes Gerardus Petrus Goossens,Pieter Jan Lemstra 한국고분자학회 2012 Macromolecular Research Vol.20 No.10
The dispersion of starch as a filler in hydrophobic ethylene-co-vinyl acetate (EVA) rubber is an issue. To obtain a fine dispersion of starch in EVA rubber, EVA/starch blends were prepared by reactive extrusion in the presence of maleic anhydride (MA), benzoyl peroxide (BPO), and glycerol. MA, BPO, and glycerol play the role of coupling agent, free-radical initiator, and plasticizer, respectively. Molau experiment and Fourier transform infrared spectroscopy (FTIR) results showed that EVA chains were grafted onto the surface of starch particles during reactive extrusion via a free-radical grafting mechanism. As a result, EVA-g-starch copolymers acted as a compatibilizer,leading to fine dispersion of starch and strong interfacial adhesion between the starch and the EVA matrix. Scanning electron microscope (SEM) images showed that the starch particle size reduced from hundreds micrometers in the case of physical blending to approximately 1 micrometer in the case of reactive blending, and consequently, the EVA rubber was effectively reinforced by the incorporation of starch and the reactive compatibilization (e.g., the tensile strength of the EVA/starch (50/50, wt/wt) was increased by a factor of 6 after the addition of 0.9-1.8 wt% MA). The property stability of starch compounds is usually an issue, while the mechanical properties of the (compatibilized)EVA/starch blends reported in this article were stable during storage
Fair Resource Allocation with QoS Guarantee in Secure Multiuser TDMA Networks
Bai, Zhiquan,Wang, Tongtong,Ma, Piming,Ma, Yanbo,Kwak, Kyungsup WILEY INTERSCIENCE 2018 WIRELESS COMMUNICATIONS AND MOBILE COMPUTING Vol.2018 No.-
<P>We investigate a secure multiuser time division multiple access (TDMA) system with statistical delay quality of service (QoS) guarantee in terms of secure effective capacity. An optimal resource allocation policy is proposed to minimize the <TEX>$ \beta $</TEX> -fair cost function of the average user power under the individual QoS constraint, which also balances the energy efficiency and fairness among the users. First, convex optimization problems associated with the resource allocation policy are formulated. Then, a subgradient iteration algorithm based on the Lagrangian duality theory and the dual decomposition theory is employed to approach the global optimal solutions. Furthermore, considering the practical channel conditions, we develop a stochastic subgradient iteration algorithm which is capable of dynamically learning the intended wireless channels and acquiring the global optimal solution. It is shown that the proposed optimal resource allocation policy depends on the delay QoS requirement and the channel conditions. The optimal policy can save more power and achieve the balance of the energy efficiency and the fairness compared with the other resource allocation policies.</P>