Gasification of waste tires in a circulating fixed-bed reactor within the scope of waste to energy

Clean Technologies and Environmental Policy - Thermochemical decomposition of waste tires was evaluated in order to produce solid and gaseous products within the aim of waste-to-energy concept....     

Are RNGs Achilles’ Heel of RFID Security and Privacy Protocols?

Security and privacy concerns have been growing with the increased utilisation of RFID technology in our daily lives. To mitigate these issues, numerous privacy-friendly authentication protocols have been published in the last decade. Random number generators (RNGs) are necessarily used in RFID tags to provide security and privacy. However, low-end RNGs can be the weakest point in a protocol scheme and using them might undesirably cause severe security and privacy problems. On the other hand, having a secure RNG with large entropy might be a trade-off between security and cost for low-cost RFID tags. Furthermore, RNGs used in low-cost RFID tags might not work properly in time. Therefore, we claim that the vulnerability of using an RNG deeply influences the security and privacy level of the RFID system. To the best of our knowledge, this concern has not been considered in the RFID literature. Motivated by this need, in this study, we first revisit Vaudenay’s privacy model which combines the early models and presents a new mature privacy model with different adversary classes. Then, we extend the model by introducing RANDOMEYE privacy, which allows analyzing the security of RNGs in RFID protocols. We further apply our extended model to two existing RFID schemes.     

Field and laboratory performance comparison for asphalt mixtures with different moisture conditioning systems

The purpose of this study is to compare laboratory and field performances for dense graded asphalt mixtures. Control road pavement section was constructed in Black Sea Coast Highway. Marshall identical control samples produced in laboratory and core samples taken from wearing courses before the traffic opened were used. Three different moisture conditioning methods were applied to control laboratory and core samples. Mechanical properties of samples were evaluated with indirect tension, indirect tension strength and repeated creep tests. Indirect tensile strength test results for laboratory mixtures were found 1.22 and 1.30 times more in accordance with field samples at 10 °C and 20 °C respectively. Marshall samples gave higher resilient modulus for all control and conditioned mixtures. Repeated creep test results also proved the difference between laboratory and field sample performance. Laboratory samples protected their structural integrity along with the test duration and did not showed tertiary creep. It is concluded from this study that laboratory samples state expressly higher performance according to the core field samples.     

Nanoscale communication with molecular arrays in nanonetworks

Molecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 μs and 2 nm, respectively.     

An integrated fuzzy-lp approach for a supplier selection problem in supply chain management

In supply chain management process, the firm select best supplier takes the competitive advantage to other companies. Thus, supplier selection is an important issue and with the multiple criteria decision-making approach, the supplier selection problem includes both tangible and intangible factors. This paper is aimed to present an integrated fuzzy and linear programming approach to the problem. Firstly, linguistic values expressed in trapezoidal fuzzy numbers are applied to assess weights and ratings of supplier selection criteria. Then a hierarchy multiple model based on fuzzy set theory is expressed and fuzzy positive and negative ideal solutions are used to find each supplier’s closeness coefficient. Finally, a linear programming model based on the coefficients of suppliers, buyer’s budgeting, suppliers’ quality and capacity constraints is developed and order quantities assigned to each supplier according to the linear programming model. The integrated model is illustrated by an example in a textile firm.     

Hydrogen sorption characteristics of Zonguldak region coal activated by physical and chemical methods

Hydrogen sorption characteristics of activated carbons (ACs) produced by physical and chemical activations from two coal mines (Kilimli and Armutcuk) in the Zonguldak region, Turkey were investigated by a volumetric technique at 77 K. H₂ adsorption isotherms were obtained on the samples exposed to pyrolytic thermal treatments in a temperature range of 600–900 °C under N₂ flow and chemical activation using different chemical agents such as KOH, NH₄Cl, ZnCl₂ from the two mines. Experimental hydrogen adsorption isotherm data at 77 K were used for the evaluation of the adsorption isotherm constants of the Brunauer-Emmett-Teller (BET) and the Langmuir models, and also the amount of hydrogen adsorbed on the various samples was evaluated by using the adsorption isotherm data. Higher hydrogen adsorption capacity values were obtained for all the heat and the chemically treated activated carbon samples from the Kilimli coal samples than Armutcuk. The amount of H₂ adsorbed on the original Kilimli coal samples was 0.020 wt%, and it was increased to 0.89 wt% on the samples pyrolyzed at 800 °C. The highest value of hydrogen adsorption obtained was 1.2 wt% for the samples treated with KOH+NH₄Cl mixture at 750 °C followed by oxidation with ZnCl₂. It was shown that chemical activations were much more effective than physical activations in increasing the surface area, pore volume and the hydrogen sorption capacities of the samples.     

Distributed audio sensing with homeostasis-inspired autonomous communication

Emerging applications of wireless sensor networks (WSN) requiring wide-band event signal communication such as multimedia surveillance sensor networks impose additional challenges including high communication bandwidth requirement and energy cost. Besides their partially or fully dependency on feedback messages from sink node, the existing protocols designed for WSN do not address the communication of wide-band event signals. Furthermore, the feedback messages may not reach in time to provide reliable communication of event information and save scarce network resources. Therefore, an autonomous communication protocol is imperative in order to provide wide-band event signal communication without any feedback from the sink. In nature, biological systems have self-organization capability, i.e., homeostasis, as they autonomously maintain a relatively stable equilibrium state for operation of vital functions. Hence, this natural phenomenon clearly gives promising inspirations in order to develop autonomous and efficient communication models and protocols for WSN domain. In this paper, the homeostasis-inspired autonomous communication (HAC) protocol is introduced for wireless audio sensor networks (WASN). Using the spectral properties of the wide-band event signal, i.e., audio signal, HAC enables WASN to maintain a relatively stable state in which sensor nodes reliably and energy-efficiently communicate the event signal to the sink node. Furthermore, with its self-organization capability, HAC does not rely on any feedback message from the sink node. Performance evaluations reveal that HAC successfully communicates wide-band event signal with minimum energy expenditure.     

Selective thermal recycling for graphene growth on natural substrates: A comparative study on life cycle assessment,energy consumption,and mechanical performance in recompounding

Manufacturing of carbon-based materials from waste thermoplastics is a keystone to reduce adverse environmental impacts. There are numerous attempts for sustainable graphene manufacturing from various waste sources by thermal treatment but there is no clear distinction on the effective conversion process by addressing reliable CO₂ footprints. This study provides a comprehensive benchmarking study on the conversion of waste polypropylene plastics coming from yogurt containers into graphene on the substrate of talc by applying two upcycling techniques of catalytic carbonization (CC) and flash pyrolysis (FP) by comparing energy and speed of the processes and a dimensional stability and physical characteristics of the produced graphene substances by adopting a comparative life cycle assessment. FP led to the sphericalization of graphenes due to fast dehydration, cross-linking, and carbonization of aromatic structures. On the other hand, gradual heating in CC caused the formation of tubular-like graphene structures. In addition, FP became advantageous by resulting in 52% of CO₂ emission compared with CC process. On the other hand, graphenes separated from talcs exhibited a remarkable 70% reduction in global warming potential compared with conventional graphene production from graphite. In order to complete the value chain and circularity, the mechanical performance of two different hybrid additives produced by selective thermal recycling in recompounding with copolymer polypropylene was examined, and additives from CC enhanced the flexural and tensile properties two times better than the one from FP. With this study, it becomes possible to compare analysis of graphene growth on natural substrates by exploring life cycle assessment, energy consumption, and mechanical performance with selective thermal recycling and recompounding.