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J. Ahmad

Publications and source records attributed to J. Ahmad.

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Resolving the Decreased Rank Attack in RPL's IoT Networks

The Routing Protocol for Low power and Lossy networks (RPL) has been developed by the Internet Engineering Task Force (IETF) standardization body to serve as a part of the 6LoWPAN (IPv6 over Low-Power Wireless Personal Area Networks) standard, a core communication technology for the Internet of Things (IoT) networks. RPL organizes its network in the form of a tree-like structure where a node is configured as the root of the tree while others integrate themselves into that structure based on their relative distance. A value called the Rank is used to define each node's relative position and it is used by other nodes to take their routing decisions. A malicious node can illegitimately claim a closer position to the root by advertising a lower rank value trapping other nodes to forward their traffic through that malicious node. In this study, we show how this behavior can have a detrimental side effect on the network via extensive simulations and propose a new secure objective function to prevent such an attack.

cs.NI

Understanding the Impact of Customer Reviews on Hotel Rating: An Empirical Research

The ascent of the Internet has caused numerous adjustments in our lives. The Internet has radically changed the manner in which we carry on with our lives, the manner in which we spend our occasions, how we speak with one another day by day, and how we buy items. The development of the Internet among users has created content on the Internet by sources, for example, web-based life, reviews site, online journals, item fan page and some more. This has a lead on to another method for arranging an occasion or searching for a reasonable hotel to remain. Thus, hotel review sites have turned into a famous stage for visitors to share their experiences, reviews, and suggestions on hotels, which they have visited. In Europe, the hotel business has been a standout amongst the most vital monetary developments of the nation. The essential objective of a hotel is to satisfy the customers, to have the capacity to give a high caliber of administration and give them a vital affair while remaining at the hotel. The motivation behind this examination is to comprehend and recognize the scope of elements, which may add as per the general inclination of customers and in addition through their reviews to decide the measures of customers' desires. Information was gathered from online review sites, for example, Booking.com. Text analytics is utilized to analyze the contents gathered.

cs.CY

Magnetoelectric Phase Diagrams of Multiferroic GdMn2O5

Electric and magnetic properties of multiferroic GdMn2O5 in external magnetic fields were investigated to map out the magnetoelectric phases in this material. Due to strong magnetoelectric coupling, the dielectric permittivity is highly sensitive to phase boundaries in GdMn2O5, which allowed to construct the field-temperature phase diagrams. Several phase transitions are observed which are strongly field-dependent with respect to field orientation and strength. The phase diagram for a magnetic field along the crystallographic a-axis corresponds well to a polarization step, as induced by 90 degree rotation of Gd magnetic moments. Our results support the model of two ferroelectric sublattices, Mn-Mn and Gd-Mn with strong R-Mn (4f-3d) interaction for the polarization in RMn2O5.

cond-mat.mtrl-sci

Optical phonons in new ordered perovskite Sr2Cu(Re0.69Ca0.31) Oy system observed by infrared reflectance spectroscopy

We report infrared reflectivity spectra for a new correlated cupric oxide system Sr2Cu(Re0.69Ca0.31)Oy with y ~ 0.6 at several temperatures ranging between 8 and 380 K. The reflectivity spectrum at 300 K comprises of several optical phonons. A couple of residual bands located around 315 and 653 cm-1 exhibit exceptionally large intensity as compared to the other ones. The overall reflectivity spectrum lifts up slightly with increasing temperature. The energy and damping factor of transverse-optical phonons are determined by fitting the imaginary dielectric constant by Lorentz oscillator model and discussed as a function of temperature in terms of lattice anharmonicity.

cond-mat.str-el