Technological Educational Institute of Western Macedonia

About: Technological Educational Institute of Western Macedonia is a based out in . It is known for research contribution in the topics: Catalysis & Symplectic geometry. The organization has 291 authors who have published 522 publications receiving 7682 citations. The organization is also known as: TEI of West Macedonia & TEI of Western Macedonia.

Middleware IoT protocols performance evaluation for carrying out clustered data

Abstract: Several IoT middleware protocols have been proposed for the wireless transfer of IoT data. The main representatives are the CoAP, the SOAP, the MQTT and the HTTP protocols. The main concerns on these technologies are the delay, packet loss, processing effort and power consumption that IoT devices demand, in order to successfully transfer wireless data to the cloud. In exchange for the reduction of the power consumption, many of these technologies try to lower the data throughput, minimize security, or even reduce the distance range of device coverage. In this paper authors compare the performance of IoT application protocols, based on M2M delay and the extra payload that they enforce to the transmitted data. Experimentation tests reveal which protocol is best suited for different network and application scenarios accordingly.

A Sizing Method for Decentralized Energy Storage Systems Operating Under a Peak Shaving Control Strategy

Abstract: Decentralized energy storage systems (ESSs) can provide great advantages to low-voltage (LV) distribution networks, enhancing the further penetration of photovoltaic (PV) systems in existing electrical grids. An ESS can locally absorb the PV produced energy during periods of high solar irradiation, thus alleviating potential overvoltages in distribution system, caused by reverse power flow. This work investigates the impact of battery ESSs operation when installed in residential PV prosumers. The charging process of the battery is activated when PV power exceeds a certain power threshold, mitigating the generation peaks in the grid. A sizing method is developed to estimate the capacity of ESSs, aiming to maximize prosumer self-consumption ratio (SCR). The proposed methodology is tested in a real LV network with increased PV integration. Results verify the effectiveness of the developed method. Overvoltages are successfully avoided while prosumers’ SCR is maximized and storage utilization is preserved high. The methodology may constitute a useful tool for both distribution system operators and prosumers having storage systems.

Nanocomposites of poly(3‐hydroxybutyrate)/organomodified montmorillonite: Effect of the nanofiller on the polymer's biodegradation

Abstract: Poly(3-hydroxybutyrate) (PHB) is a biopolymer that can be degraded by extracellular PHB depolymerase. This enzyme is secreted by various microorganisms, but bacterial PHB depolymerases are the most widely studied. The biodegradability rate depends on various factors. By controlling them, the biodegradability rate can change and be customized, and thus, the applications of the polymer can increase and become more diverse. In this work, the role of organomodified montmorillonite (OMMT) on PHB biodegradation was investigated. Using the melt-mixing method, nanocomposites of PHB and OMMT as the nanofiller were prepared. The enzyme was isolated from the fungus Penicillium pinophilum and the enzymatic degradation was studied for both pure polymer and its nanocomposites. It was found that, after 25 days of enzymatic degradation, the mass loss was very low, while the polymer's average molecular weight as measured by gel permeation chromatography was significantly reduced (more than 50%). Additional peaks corresponding to PHB oligomers (from pentamers to nonamers) appeared after biodegradation. This behavior was observed for pure PHB and the hybrid materials. Scanning electron microscopy imaging of the biodegraded surfaces and analysis of these images showed that the higher amount of nanoclay (10 wt %) resulted in larger biodegraded area of the specimens. The results presented here demonstrate that the presence of the nanoclays enhances the biodegradation rate of pure PHB polymer and provide quantitative data for the biodegradation of PHB/organoclay hybrid materials. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41656.