A hotel recommendation system based on customer location: a link prediction approach

Multimedia Tools and Applications - Hotel recommendation is one of the most used application areas in recommendation systems. So far, many hotel recommendation systems have been proposed. Most of...     

Analyzing the determinants of carbon emissions from transportation in European countries: the role of renewable energy and urbanization

Clean Technologies and Environmental Policy - The continuous growth of transport sector and the increase in carbon emissions from transportation attract the attention of policy makers in...     

Managing cohort movement of mobile sensors via GPS-free and compass-free node localization

A critical problem in mobile ad hoc wireless sensor networks is each node’s awareness of its position relative to the network. This problem is known as localization. In this paper, we introduce a variant of this problem, directional localization, where each node must be aware of both its position and orientation relative to its neighbors. Directional localization is relevant for applications that require uniform area coverage and coherent movement. Using global positioning systems for localization in large scale sensor networks may be impractical in enclosed spaces, and might not be cost effective. In addition, a set of pre-existing anchors with globally known positions may not always be available. In this context, we propose two distributed algorithms based on directional localization that facilitate the collaborative movement of nodes in a sensor network without the need for global positioning systems, seed nodes or a pre-existing infrastructure such as anchors with known positions. Our first algorithm, GPS-free Directed Localization (GDL) assumes the availability of a simple digital compass on each sensor node. We relax this requirement in our second algorithm termed GPS- and Compass-free Directed Localization (GCDL). Through experimentation, we demonstrate that our algorithms scale well for large numbers of nodes and provide convergent localization over time, despite errors introduced by motion actuators and distance measurements. In addition, we introduce mechanisms to preserve swarm formation during directed sensor network mobility. Our simulations confirm that, in a number of realistic scenarios, our algorithms provide for a mobile sensor network that preserves its formation over time, irrespective of speed and distance traveled. We also present our method to organize the sensor nodes in a polygonal geometric shape of our choice even in noisy environments, and investigate the possible uses of this approach in search-and-rescue type of missions.     

Pyroelectric and dielectric properties of spin‐coated thin films of vinylidene fluoride–trifluoroethylene copolymers

This work emphasizes the use of vinylidene fluoride and trifluoroethylene copolymer P(VDF‐TrFE) as a pyroelectric sensor. The pyroelectric and dielectric properties of the copolymer have been investigated in the temperature interval 150–350 K. The samples were prepared by using a spin‐coating technique with 70/30 mol% VDF/TrFE copolymer. The final film thickness of the samples, which is mainly determined by the concentration of the copolymer, spinning rate and spin time, was measured with a surface profiler. The samples were annealed at 150 °C for 10 min to improve the crystallinity of the copolymer. The crystallinity of the annealed and non‐annealed samples was compared by IR spectroscopy. The most effective process by which to improve the pyroelectric response of the material is to pole the sample with huge poling field‐strengths at elevated temperatures. Both pyroelectric and dielectric activities of the samples were measured after each successful poling process. It was observed that while the pyroelectric activity of the material increases, the dielectric activity decreases, so the figure‐of‐merit of the material, which shows the sensor capability of the material, was increased by a significant amount. It was found that the pyroelectric coefficient of VDF/TrFE (70/30 mol%) copolymer is 68.7 µC m^?2 K^?1 at 300 K. © 2001 Society of Chemical Industry     

Factors affecting the shape of lactation curves of Holstein cows from the Balikesir Province of Turkey

The shape of the lactation curve for 475 Turkish Holsteins was estimated by fitting a gamma function to daily milk yields from monthly recording of 754 lactations. Lactation curve traits that were analyzed included a scaling factor associated with yield at the beginning of lactation, the inclining and declining slopes before and after peak yield, DIM at peak yield, and peak and lactation yields. Persistency of lactation yield was measured from 1) the gamma function, 2) the coefficient of variation for monthly test-day yields, and 3) the ratio of lactation yield to peak yield. The log-transformed gamma function explained 71% of variation in daily yield. Effects of farm operation, calving year, calving season, parity, and service period were significant for the various lactation curve traits. Peak and lactation yields were higher for cows that calved in fall and winter, and persistency was higher for cows that calved in summer and fall. Peak and lactation yields were lower, but persistency was higher during first lactation. Repeatability estimates were moderate for peak (0.26) and lactation (0.34) yields and lower (0.06 to 0.20) for other lactation curve traits.     

COMPARATIVE STUDY OF Ag2O/CO3O4 CATALYSTS PREPARED BY THE SOL-GEL AND CO-PRECIPITATION TECHNIQUES: CHARACTERIZATION AND CO ACTIVITY STUDIES

In this study effects of the preparation method on the characteristic properties and CO oxidation activities of Ag₂O/Co₃O₄ catalysts were investigated. Catalysts were prepared by two different methods: sol gel and co-precipitation. N₂ physisorption measurements, X-ray diffraction, and scanning electron microscopy measurements were used to characterize the catalysts. CO oxidation activity tests were carried out under 1% CO, 21% O₂, and the remainder He feed condition between 20° and 200°C. According to the N₂ physisorption measurements, catalysts prepared by the co-precipitation method have a higher surface area than the catalysts prepared by the sol-gel method. Co₃O₄ and AgCoO₂ phases were obtained from catalysts prepared by both techniques. In addition to these phases, metallic silver peaks were obtained by increasing calcination temperature. SEM micrographs of the catalysts showed that catalysts have uniform particles. Increasing the calcination temperature caused the formation of different-sized agglomerates and an increase in the gaps between agglomerates. The best activity was obtained from the Ag₂ O/Co₃ O₄ catalyst calcined at 200°C and prepared by the co-precipitation method. This catalyst gave 50% CO conversion at 106°C. The other two catalysts gave 100% CO conversion at a higher temperature of 200°C.     

Electrocatalytic oxidation of sodium borohydride on metal ad-atom modified Au(111) single crystal electrodes in alkaline solution

The electrochemical oxidation of borohydride was investigated by using various ad-atom modified Au(111) electrodes in alkaline media in comparison to Au(111) single crystal, polycrystalline Au, Pt and Zn electrodes. The catalytic activity of gold towards borohydride oxidation has tended to increase in more alkaline media as reflected in the oxidation peak in the concentration range of NaOH (0.01-2.0 M) studied. Additional shift on the oxidation peak potential of borohydride on Pt and Zn ad-atom modified Au(111) electrodes was observed for both ad-atom modified electrodes to more negative potentials compared to that of bare electrodes, respectively. The ad-atom modified Au(111) electrodes surfaces do not only provide a superior electrical contact, but also accelerates electron transfer as proven by the increase in peak current and positive shift in the peak potential.