The World Health Organization (WHO) reported that there are 285 million visually-impaired people worldwide. Among these individuals, there are 39 million who are totally blind. There have been several systems designed to support visually-impaired people and to improve the quality of their lives. Unfortunately, most of these systems are limited in their capabilities. In this paper, we present a comparative survey of the wearable and portable assistive devices for visually-impaired people in order to show the progress in assistive technology for this group of people. Thus, the contribution of this literature survey is to discuss in detail the most significant devices that are presented in the literature to assist this population and highlight the improvements, advantages, disadvantages, and accuracy. Our aim is to address and present most of the issues of these systems to pave the way for other researchers to design devices that ensure safety and independent mobility to visually-impaired people.
Simulating blockchain technology within the IoT has never been as important. Along with this comes the need to find suitable blockchain simulators capable of simulating blockchain networks within an IoT environment. Despite there being a wide variety of blockchain simulators, not all are capable of simulating within an IoT environment and not all are suitable for every IoT environment. This article will review previously published works and present a list of suitable blockchain simulators as well as a few untested simulators that have the potential to simulate blockchain networks within an IoT environment. A total of 18 blockchain simulators are presented and discussed in this paper. In addition, a comprehensive list of the advantages and limitations of each simulator is presented to demonstrate the best situation in which simulators should be used. Finally, recommendations are made on when each simulator should be used and in what situation it should be avoided.
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