In many applications of Wireless Sensor Networks (WSNs), the sensing data are disseminated from a source to multiple mobile sinks. Since WSNs consists of a number of sensor nodes with limited capabilities, previous studies mainly discuss on how to send the data efficiently and do not consider the group mobility of mobile sinks that move together staying closely and randomly move within a geographically restricted region. Although the existing multicasting protocols could be applied, they suffer from high congestion and control overhead due to location updates by individual mobile sinks. Geocasting protocols are effective for data delivery to a sink group within a restricted region, but do not guarantee since they only focus on transmitting data to all nodes within a stationary region. Therefore, we propose Region Based Data Dissemination (RBDD) scheme to address these problems. RBDD provides efficient data dissemination scheme for mobile sink groups, so it guarantees data transmission not only when a sink group does move as a whole, but also its member sinks move inside of the region or outside of it. Simulation results show that RBDD guarantees data delivery to a mobile sink group.
This experimental study examined the aplication effect of polycaprolactone (PCL), an organic resin material with excellent elasticity and ductility, on improving the mechanical performance of cellulose nanocrystal (CNC) cement composites. PCL was compared according to its shape, and in the case of Granules, which is the basic shape, interfacial adhesion with cement was not achieved, so a dichloromethane (DCM) solution was used to dissolve and use the Granules form. As a method for bonding PCL to the CNC surface, the CNC surface was modified using 3-aminopropyltriethoxysilane (APTES), and surface silylation was confirmed through Fourier transform infrared spectroscopy (FT-IR) analysis. In order to evaluate the dispersibility according to the application of PCL to the modified CNC, particle size analysis (PSA) and zeta potential analysis were performed according to the PCL mixing ratio. Through the PSA and zeta potential values, the highest dispersion stability was shown at 1 vol.%, the cohesive force of CNC was low, and the dispersion stability was high according to the application of PCL. According to the results of the dispersion stability evaluation, the degree of hydration of the dissolved PCL 1 vol.%, CNC-only specimens, and plain specimens were analyzed. CNC acted as a water channel inside the cement to accelerate hydration in the non-hydrated area, resulting in an increased degree of hydration. However, the incorporation of PCL showed a low degree of hydration, and the analysis of strength characteristics also showed a decrease of approximately 27% compared with that of plain specimens. This was because the bonding with SiO2 was not smooth owing to the solvent, thus affecting internal hydration. In order to investigate the effect of the PCL shape, the compressive and flexural strength characteristics were compared using PCL powder as an additional parameter. The compressive strength and flexural strength were improved by about 54% and 26%, respectively, in the PCL powder 15 wt% specimen compared to the general specimen. Scanning electron microscopy (SEM) analysis confirmed that the filler effect, which made the microporous structure denser, affects the mechanical performance improvement.
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