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Wireless communication technology experienced drastic developments during the last few decades. Meanwhile the reconfigurable antenna had attracted more researchers because of its growing needs in various applications. Reconfiguration was performed to replace numerous antennas with single reconfigurable antenna which is capable of changing the Frequency, Polarization, Radiation Pattern etc. Antenna reconfigurability is attained by deploying several switching mechanisms among them electronic switching mechanisms are commonly used because of its simple integration, reliability, and efficiency. In this paper, review of various implementation techniques for antenna reconfiguration using meta surface are studied. Some of the reviewed factors are: Meta surface is the distribution of electrically small scatters called two-dimensional metamaterial. Metamaterial is an artificially built periodic array structure which consists of subwavelength cells. Some of the reviewed challenges in reconfiguration of the antenna are modeling of reconfigurable reflectarray, low-profile, high gain, unidirectional radiation pattern etc. Finally, some of the features, parameters and fundamental properties for designing reconfigurable antenna were investigated. Based on the study conducted, reconfigurable structure for 5 G application using meta surface is proposed.

Sign language is the most putative language among hearing impaired people. They use non-verbal form of communication that involves hand gestures, head or body movement or facial expressions. Of these hand gestures is more widely used. Automatic Sign Language Recognition (ASLR) System can be used to convert these non-verbal signs into text or sound so that normal people can identify them without learning the sign language. ASLR employs Image Processing and Artificial Intelligence (AI) algorithms for effective conversion from sign to sound or text. This review unveils various image processing and AI steps involved in the conversion process, bringing out important topologies in the Image acquisition, segmentation, feature extraction, classification and detection process and a comparative analysis among various topologies. Attempts have been made to shed light into adoption of alternate design strategies in segmentation and feature extraction that enhance the performance in a complex environment.

Organic Light Emitting Diodes (OLED) are receiving increased attention due to tremendous application potential these devices hold in the areas of large area displays and lighting applications. However, the problems of efficiency, stability and shelf life are major challenges for making OLEDs an attractive alternative. The simple device structure involving anode, emissive layer and cathode is no longer the norm. Recently, various buffer layers like Hole Injection Layer (HIL), Hole transport Layer (HTL), Electron Injection Layer (EIL), Electron Transport Layer (ETL) etc. are being widely used as integral parts of the OLED architecture to enhance the performance parameters. The nomenclature of these layers is often confusing and sometimes used by different authors to mean different layers and a common and universal nomenclature for layers is still wanting. Applying a buffer layer, often called as the hole injecting layer (HIL) between anode and emissive layer is a general technique for increasing the efficiency and stability of organic light emitting diodes. Poly- (3,4-ethyhylene dioxythiophene): poly- (styrenesulphonate) (PEDOT:PSS) is a very common and popular such HIL used in OLEDs. In this chapter, a basic structure of OLEDs has been discussed in perspective with this HIL material and the effect of annealing this PEDOT: PSS layer on the characteristics of the device at different temperatures ranging from 100°C to 300°C in vacuum. Devices fabricated in clean room conditions are characterized for their electrical and optical properties. Equivalent circuits of the devices are deduced using impedance spectroscopy and discussed. Surface morphology of the HIL layers using atomic force microscopy (AFM) provides reasons for the variation of the device properties with the annealing of HIL.

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