**Zahir Shah 1,\*, Ebraheem Alzahrani 2, Muhammad Jawad 3 and Umair Khan 4**

Received: 28 August 2020; Accepted: 16 October 2020; Published: 19 October 2020

**Abstract:** In this research work, our goal is to scrutinize the case, where water-based nanofluids having single-wall and multi-wall carbon nanotubes (CNTs) flow through a vertical cone. The second law of thermodynamic is taken for the aim of scheming effective heat storage units. The body package is layered in convective heat and diluted permeable medium. The effects of Joule heating, rotary microorganisms, heat generation/absorption, chemical reactions, and heat radiation increase the novelty of the established model. By using a local similarity transformation technique, the partial differential equations (PDEs) change into a coupled differential equation. By using the numerical technique, bvp4c, to get the solution of the conservation equations and their relevant boundary conditions. The parameters appearing in the distribution analysis of the alliance are scrutinized in detail, and the consequences are depicted graphically. It can be perceived that in the situation of composed nanotubes, the velocity of fluid decreases as the magnetic field is increased.

**Keywords:** gyrotactic microorganisms; micropolar magnetohydrodynamics (MHD); Maxwell nanofluid; single wall carbon nanotubes (SWCNTs) and multi wall carbon nanotubes (MWCNTs); thermal radiation; chemical reaction; mixed convection; permeability


**2.3 Blockchain technology**

Blockchain is a distributed ledger (register) technology that achieves immutability, traceability, anonymity, security, transparency, and decentralization through the use of consensus algorithms and cryptographic methods. All nodes on the blockchain verify and record confirmed transactions with a timestamp. The distribution of the ledger among the blockchain network's members provides transparency. Security of the information kept in the record is ensured and cannot be obstructed. One of the most important aspects of blockchain is the smart contract. It is a short piece of code that is part of the blockchain and can be executed automatically if the conditions are met. Blockchain is known to be of three types: These include consortium, public, and private blockchains. A private blockchain is more trusted by participants because it is managed by a single organization and governs its activities, such as who can participate in the blockchain. Any entity can participate in a public blockchain, which does not require permission. Privacy, security, and performance are among its drawbacks due to its highly decentralized nature. A permissioned blockchain created by a group of different businesses is known as a consortium blockchain. Nodes are the entities in this kind of blockchain. Which organizations or entities participate in the blockchain is controlled by the consortium [4].

The Internet of Things (IoT) has been the primary beneficiary of blockchain technology's features, such as the decentralized characteristics that enable devices to connect and share sensitive data securely in an IoT environment. These applications include auctions, mutual authentication, and blockchain technology. Blockchain is able to provide authentication systems with a dependable computational platform and secure storage thanks to these characteristics. A consensus algorithm helps the devices in a blockchain network establish trust. This makes it possible for devices to keep cryptographic keys (both private and public keys) and a digital signature. This makes it easier for devices in the network to communicate and transact. These transactions are tamper-proof on the blockchain network because they cannot be changed [4].

*A Simulation Model of a Blockchain-Based Decentralized Patient Information Exchange… DOI: http://dx.doi.org/10.5772/intechopen.109591*

A blockchain is designed to resist data modification. It is "an open, distributed ledger that can efficiently and permanently record transactions between two parties." A blockchain is typically managed by a peer-to-peer network that collectively adheres to a protocol for inter-node communication and block validation in order to function as a distributed ledger. The data in any given block cannot be changed after it has been recorded without changing all subsequent blocks, which requires the majority of the network. Blockchains may be considered as secure by design and represent a distributed computing system with high Byzantine fault tolerance (any fault presenting different symptoms to different observers), despite the fact that their records can be changed. As a result, a blockchain has been advertised as providing decentralized consensus [6]. **Figure 2** represents the functional diagram of Blockchain.