This paper proposes an adaptive hierarchical MAC protocol (AH-MAC) with cross-layer optimization for low-rate and large-scale wireless sensor networks. The main goal of the proposed protocol is to combine the strengths of LEACH and IEEE 802.15.4 while offsetting their weaknesses. The predetermined cluster heads are supported with an energy harvesting circuit, while the normal nodes are battery-operated. To prolong the network’s operational lifetime, the proposed protocol transfers most of the network’s activities to the cluster heads while minimizing the node’s activity. Some of the main features of this protocol include energy efficiency, self-configurability, scalability, and self-healing. The simulation results showed great improvement of the AH-MAC over LEACH protocol in terms of energy consumption and throughput. AH-MAC consumes eight times less energy while improving throughput via acknowledgment support.

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Detection of pornographic images can effectively prevent pornographic images from spreading on the Internet. This research proposes a new approach of pornographic images detector. Naive Bayesian classifier is used by the proposed detector to identify potential pornographic images. Skin and non-skin color models are constructed and exploited by constructing a Bayesian decision rule based skin detector. Several features are extracted from the output of skin detector which forms the features vector. The naive Bayesian classifier is trained on these features for both porn and non-porn classes. An experiment used Constructing Pornographic Images Detector based on naïve Bayesian classifier. ٨٥ (136) images for training the pornographic images detector and (154) images for testing it. The pornographic images detector is evaluated by using sensitivity, precision, specificity and accuracy metrics. It achieves a detective rate of (91.48%) with (6.67%) false positive rate.

This paper investigates many drawbacks and limitations of current clustering algorithms designed for wireless sensor networks. These limitations include high resource requirements, significant overhead, tight synchronization requirements, and TDMA limitations. A new clustering algorithm called hybrid access and an adaptive duty cycle clustering (HADC) protocol is introduced, aiming to address the previous limitations. HADC protocol is based on several concepts, including static clusters, adaptive duty cycling, hybrid scheme channel access, minimum node's functionality, and pseudo synchronization. The resulting network's important features are energy efficiency, robustness, low latency, scalability, and self-healing. The functionality of HADC is validated by both simulation and laboratory experiments. Simulation results show significant improvement of HADC over the well-known LEACH protocol in terms of energy, latency, and packet delivery ratio. The experiment results show that the node's lifetime with two 3000 mAh batteries and transmitting four packets per minute is about 16 years. The lifetime of the cluster head supported by the same energy sources ranges from 110 to 472 days. HADC is the first clustering algorithm designed for sporadic and low rate WSN applications to the best of authors' knowledge.

Radiation by a microstrip patch antenna is well understood. Although typically such antennas are fed in a manner to achieve linear polarization, circular polarization is also of interest. Of more recent interest is the use of engineered composite materials (e.g. metamaterials) to control radiation. In some cases, inherently anisotropic materials have been characterized using isotropic inversion methods. Radiation through an isotropic material is fundamentally different than that of the true anisotropic material. In this paper, radiation of such an antenna through a uniaxial superstrate is investigated to demonstrate the hazard of using isotropic material properties for an inherently anisotropic material. One of the primary effects involves the distortion of radiated field polarization.Keywords-microstrip patch antenna; metamaterial; uniaxial superstrate; finite element method; measured material properties.