Ábel Simon - Academia.edu (original) (raw)

Papers by Ábel Simon

$Research paper thumbnail of On the R\'enyi-Ulam Game with Restricted Size Queries$

arXiv (Cornell University), Apr 4, 2021

We investigate the following version of the well-known Rényi-Ulam game. Two players-the Questione... more We investigate the following version of the well-known Rényi-Ulam game. Two players-the Questioner and the Responder-play against each other. The Responder thinks of a number from the set {1,. .. , }, and the Questioner has to find this number. To do this, he can ask whether a chosen set of at most elements contains the thought number. The Responder answers with YES or NO immediately, but during the game, he may lie at most ℓ times. The minimum number of queries needed for the Questioner to surely find the unknown element is denoted by ℓ (). First, we develop a highly effective tool that we call Convexity Lemma. By using this lemma, we give a general lower bound of ℓ () and an upper bound which differs from the lower one by at most 2ℓ + 1. We also give its exact value when is sufficiently large compared to. With these, we managed to improve and generalize the results obtained by Meng, Lin, and Yang in a 2013 paper about the case ℓ = 1.

Polymer Degradation and Stability, 2021

Abstract We thermomechanically devulcanized ground tire rubber (GTR) in a co-rotating twin-screw ... more Abstract We thermomechanically devulcanized ground tire rubber (GTR) in a co-rotating twin-screw extruder at different barrel temperatures and screw speeds. We measured the soluble content and the cross-link density of the samples and then evaluated them by Horikx's analysis. The results showed that at lower temperatures, selective cross-link scission is dominant, and screw speed has no effect. At higher temperatures and screw speeds, the degradation of the polymer chains becomes more and more severe. With the appropriate parameters, cross-link scission can be maximized without severe degradation of the main chains. Two devulcanized ground tire rubber (dGTR) samples were chosen for further study. Natural rubber (NR) based rubber mixtures were produced with conventional and two-step mixing. Tensile and tear strength decreased significantly with dGTR content. These results are in agreement with Horikx's analysis, i.e. the greater the degradation of dGTR, the more mechanical properties were impaired. However, elongation at break did not follow such a trend. With two-step mixing, mechanical properties improved, especially tear strength. Additional experiments were also conducted with Horikx's analysis. The aim was to reveal the accuracy and usability of the analysis, and it showed the theoretical maximum of devulcanization.

Advanced Industrial and Engineering Polymer Research, 2021

Scientific Reports, 2020

We devulcanized ground tire rubber (GTR) in a laboratory microwave oven and an internal mixer, me... more We devulcanized ground tire rubber (GTR) in a laboratory microwave oven and an internal mixer, measured the soluble content and the cross-link density of the samples, and then used Horikx’s analysis. The results showed that microwave treatment caused severe degradation of the polymer chains, while in the case of thermomechanical devulcanization, the selective scission of covalent cross-links is more common. Four devulcanized ground tire rubber (dGTR) samples were chosen for further study and three groups of samples were produced: dGTR samples containing vulcanizing agents and different amounts of paraffin oil (dGTR-based mixtures), natural rubber-based rubber mixtures with different dGTR contents and reference rubber mixtures with dGTR-based mixtures (increased vulcanizing agent contents). Cure characteristics showed a plasticizer-like effect of dGTR. Tensile and tear strength decreased drastically with increasing dGTR content; however, elongation at break values did not follow such...

Periodica Polytechnica Chemical Engineering, 2019

In our current paper the preparation and properties of thermoplastic elastomer produced by dynami... more In our current paper the preparation and properties of thermoplastic elastomer produced by dynamic vulcanization is presented and discussed. We dynamically vulcanized natural and styrene butadiene rubber (NR/SBR) phase by continuous extrusion. Dispersion and in-situ vulcanization of the rubber phase occurred simultaneously in a co-rotating twin screw extruder. We used a random polypropylene copolymer (rPP) as the thermoplastic matrix and untreated crumb rubber (CR) to partially substitute the neat fresh rubber in order to check whether this is a potential recycling route for waste rubber products. We studied the effect of various rubber formulations, various processing conditions (screw speed and configuration) and various CR particle size distributions by characterizing the mechanical performance of the thermoplastic dynamic vulcanizates (TDVs) with tensile and hardness tests and their morphology by evaluating SEM micrographs taken from the fracture surfaces of the tensile specimen...

Journal of Applied Polymer Science, 2019

Rubber recycling is a major environmental challenge, as their covalently crosslinked structure ma... more Rubber recycling is a major environmental challenge, as their covalently crosslinked structure makes it impossible to reprocess via conventional polymer processing technologies. Devulcanization of rubber waste, whereby crosslinks are selectively broken, may provide a solution, as it allows it to be remolded into new shapes. We used two types of ground tire rubbers (GTRs) for this study; mechanically ground and waterjet-milled GTRs with different particle sizes. First, we revealed the effects of GTR particle size on the devulcanization process. We examined the sol content of the samples before and after devulcanization with two different microwave ovens, a power-controlled conventional one, and a temperature-controlled laboratory oven. In the latter one, heating rate and maximum temperature were controlled. We studied the effects of temperature, atmosphere in which the rubber was treated, heating rate, and holding time at maximum temperature. We prepared styrene-butadiene rubber-based rubber compounds containing GTR and optimally devulcanized GTR (dGTR_WJ). The physical and mechanical properties of the samples were assessed. The results indicate that both GTR_WJ and dGTR_WJ have an accelerating and a mildly softening effect on curing and dGTR_WJ has a less significant negative effect on mechanical properties: 15 phr GTR_WJ has the same effect as 45 phr dGTR_WJ.

Polymers, 2018

Because of the chemically crosslinked 3D molecular structure of rubbers, their recycling is a cha... more Because of the chemically crosslinked 3D molecular structure of rubbers, their recycling is a challenging task, especially when cost efficiency is also considered. One of the most straightforward procedures is the grinding of discarded rubber products with subsequent devulcanization. The devulcanized rubber can be used as a feedstock for fresh rubber compounds or can be blended with uncured virgin rubber and thermoplastic polymers to form thermoplastic dynamic vulcanizates (TDVs). TDVs combine the beneficial (re)processability of thermoplastics and the elastic properties of rubbers. Our current work focuses on the development of polypropylene (PP)-based TDVs with the use of a tire model rubber (MR) composed of natural rubber (NR) and styrene-butadiene rubber (SBR) in a ratio of 70/30. The research target was the partial substitution of the above fresh MR by microwave devulcanized crumb rubber (dCR). TDVs were produced by continuous extrusion, and the effects of composition (PP/MR/dC...

Polymers, 2016

The flame retardant synergism between highly stretched polymer fibres and intumescent flame retar... more The flame retardant synergism between highly stretched polymer fibres and intumescent flame retardant systems was investigated in self-reinforced polypropylene composites. It was found that the structure of reinforcement, such as degree of molecular orientation, fibre alignment and weave type, has a particular effect on the fire performance of the intumescent system. As little as 7.2 wt % additive content, one third of the amount needed in non-reinforced polypropylene matrix, was sufficient to reach a UL-94 V-0 rating. The best result was found in self-reinforced polypropylene composites reinforced with unidirectional fibres. In addition to the fire retardant performance, the mechanical properties were also evaluated. The maximum was found at optimal consolidation temperature, while the flame retardant additive in the matrix did not influence the mechanical performance up to the investigated 13 wt % concentration.

Radiation Physics and Chemistry