Tree-Chain: A Fast Lightweight Consensus Algorithm for IoT Applications

Blockchain has received tremendous attention in non-monetary applications including the Internet of Things (IoT) due to its salient features including decentralization, security, auditability, and anonymity. Most conventional blockchains rely on computationally expensive consensus algorithms, have limited throughput, and high transaction delays. In this paper, we propose tree-chain a scalable fast blockchain instantiation that introduces two levels of randomization among the validators: i) transaction level where the validator of each transaction is selected randomly based on the most significant characters of the hash function output (known as consensus code), and ii) blockchain level where validator is randomly allocated to a particular consensus code based on the hash of their public key. Tree-chain introduces parallel chain branches where each validator commits the corresponding transactions in a unique ledger. Implementation results show that tree-chain is runnable on low resource devices and incurs low processing overhead, achieving near real-time transaction settlement

Theoretical Reflexivity in Qualitative Research

Introduction: Theoretical reflexivity is a concept that has been widely accepted in health research and most researchers have acknowledged the importance of reflexivity in the clarity and increased accuracy of qualitative research. The purpose of this study was to introduce, explain the importance of, and describe reflexivity ‎as an important characteristic of qualitative research. Method: This research was conducted using library and internet resources without time limitation until 2015. Information was collected by searching library resources and scientific websites. Then, relevant articles were selected and their contents were extracted. Results: There are many factors for the improvement of the quality of a qualitative study; one of these factors is reflexivity‎. Reflexivity ‎is a characteristic of research that can be considered during the whole process of qualitative research and is not limited to a certain stage. It is an extensive activity in which the researcher tries to be aware of his/her ideas, attitudes, and beliefs and make their influence on his/her own research clear for him/herself and sometimes the audience. Despite the existing doubts about the ability to conduct it, almost all experts in qualitative research have emphasized its necessity in qualitative research, especially in the field of health. Creating reflexivity in qualitative research and preserving it during the development of qualitative research will increase their precision and accuracy. Conclusion: Reflexivity ‎can enrich qualitative research, improve their quality, and prevent the occurrence of bias. Therefore, attention to this factor is recommended in every step of qualitative research. ‎ Keywords: Reflexivity, Qualitative research, Theoretical reflexivity, Precisio

The Application of Structure Shift in the Persian Translation

Man as a social beings need to change what he wishes, it may be one the most desires to achieve it. In this research the researcher as a translator suffered from the wrong or unknown translation for the children. Hatim and Munday (2004) claimed that "shifts are the small linguistic changes that happen between units in a source text- target text pair"(p.265. The researcher applied the theory of Catford to concentrates on shifts utilized by the translator in the translation of children’s text named The Pearl, to compare structures of English as a source language, with its related translation counterparts of Persian, as a target language. Since the way of researching and data gathering was based on (DTS).The researcher aimed at investigating the shifts applied by translators. And accordingly to clarify the most common shifts in translating children’s texts from English to Persian and to identify the degree of correspondence between original and target. texts. The book has 1068 sentences in English that the researcher used a comparative study in Persian.. According to the theory of shift developed by Catford, there were 4 types of shifts consisted: structure, class, unit and intra system shift. The researcher found that structure shift was the essence of translation and without it, the following matters maybe occurred in translation: word for word translation, un-translatability or translation without beauty or kicking style through unawareness or ignorance of structure shift in children's translation

MOF-BC: A Memory Optimized and Flexible BlockChain for Large Scale Networks

BlockChain (BC) immutability ensures BC resilience against modification or removal of the stored data. In large scale networks like the Internet of Things (IoT), however, this feature significantly increases BC storage size and raises privacy challenges. In this paper, we propose a Memory Optimized and Flexible BC (MOF-BC) that enables the IoT users and service providers to remove or summarize their transactions and age their data and to exercise the "right to be forgotten". To increase privacy, a user may employ multiple keys for different transactions. To allow for the removal of stored transactions, all keys would need to be stored which complicates key management and storage. MOF-BC introduces the notion of a Generator Verifier (GV) which is a signed hash of a Generator Verifier Secret (GVS). The GV changes for each transaction to provide privacy yet is signed by a unique key, thus minimizing the information that needs to be stored. A flexible transaction fee model and a reward mechanism is proposed to incentivize users to participate in optimizing memory consumption. Qualitative security and privacy analysis demonstrates that MOF-BC is resilient against several security attacks. Evaluation results show that MOF-BC decreases BC memory consumption by up to 25\% and the user cost by more than two orders of magnitude compared to conventional BC instantiations

On the Activity Privacy of Blockchain for IoT

Security is one of the fundamental challenges in the Internet of Things (IoT) due to the heterogeneity and resource constraints of the IoT devices. Device classification methods are employed to enhance the security of IoT by detecting unregistered devices or traffic patterns. In recent years, blockchain has received tremendous attention as a distributed trustless platform to enhance the security of IoT. Conventional device identification methods are not directly applicable in blockchain-based IoT as network layer packets are not stored in the blockchain. Moreover, the transactions are broadcast and thus have no destination IP address and contain a public key as the user identity, and are stored permanently in blockchain which can be read by any entity in the network. We show that device identification in blockchain introduces privacy risks as the malicious nodes can identify users' activity pattern by analyzing the temporal pattern of their transactions in the blockchain. We study the likelihood of classifying IoT devices by analyzing their information stored in the blockchain, which to the best of our knowledge, is the first work of its kind. We use a smart home as a representative IoT scenario. First, a blockchain is populated according to a real-world smart home traffic dataset. We then apply machine learning algorithms on the data stored in the blockchain to analyze the success rate of device classification, modeling both an informed and a blind attacker. Our results demonstrate success rates over 90\% in classifying devices. We propose three timestamp obfuscation methods, namely combining multiple packets into a single transaction, merging ledgers of multiple devices, and randomly delaying transactions, to reduce the success rate in classifying devices. The proposed timestamp obfuscation methods can reduce the classification success rates to as low as 20%

Lightweight Blockchain Framework for Location-aware Peer-to-Peer Energy Trading

Peer-to-Peer (P2P) energy trading can facilitate integration of a large number of small-scale producers and consumers into energy markets. Decentralized management of these new market participants is challenging in terms of market settlement, participant reputation and consideration of grid constraints. This paper proposes a blockchain-enabled framework for P2P energy trading among producer and consumer agents in a smart grid. A fully decentralized market settlement mechanism is designed, which does not rely on a centralized entity to settle the market and encourages producers and consumers to negotiate on energy trading with their nearby agents truthfully. To this end, the electrical distance of agents is considered in the pricing mechanism to encourage agents to trade with their neighboring agents. In addition, a reputation factor is considered for each agent, reflecting its past performance in delivering the committed energy. Before starting the negotiation, agents select their trading partners based on their preferences over the reputation and proximity of the trading partners. An Anonymous Proof of Location (A-PoL) algorithm is proposed that allows agents to prove their location without revealing their real identity. The practicality of the proposed framework is illustrated through several case studies, and its security and privacy are analyzed in detail

Resonant electron-lattice cooling in graphene

Controlling energy flows in solids through switchable electron-lattice cooling can grant access to a range of interesting and potentially useful energy transport phenomena. Here we discuss a unique switchable electron-lattice cooling mechanism arising in graphene due to phonon emission mediated by resonant scattering on defects in crystal lattice, which displays interesting analogy to the Purcell effect in optics. This mechanism strongly enhances the electron-phonon cooling rate, since non-equilibrium carriers in the presence of momentum recoil due to disorder can access a larger phonon phase space and emit phonons more effciently. Resonant energy dependence of phonon emission translates into gate-tunable cooling rates, exhibiting giant enhancement of cooling occurring when the carrier energy is aligned with the electron resonance of the defect

Effect of cardiac rehabilitation on physical and mental health components: A randomized controlled clinical trial

Background and Aim: Cardiovascular disease can affect physical and mental conditions. The purpose of the present study was to investigate the effect of phase 1 and 2 of cardiac rehabilitation on physical and mental health components in the patients with acute coronary syndrome. Materials and methods: This clinical trial study included 50 patients with acute coronary syndrome admitted to the coronary care units of the hospitals of Isfahan University of Medical Sciences between 2013 and 2014. The participants were randomly assigned to control and experimental groups. The experimental group performed cardiac rehabilitation program and the control group received routine care. QOL-sf36 questioner was used before and one month after intervention to assess physical and mental health components. Using SPSS18 software, data were analyzed by T- test. Results: There were no significant differences in the demographic variables and cardiovascular risk factors between the experimental and control groups. The mean scores of physical component and mental component after intervention, were 40.9± 9.9 and 37.7 ±10.4 in the control group and 46.9±8.6 and 45.3±10.6 in the experimental group respectively. The results of T-test showed that the mean scores of physical (p=0.02) and mental (p=0.01) health components in the experimental group were significantly higher than those in the control group. Conclusion: The results of this study showed that cardiac rehabilitation program can improve physical and mental health components in the patients with acute coronary syndrome. © 2016, Kurdistan University of Medical Sciences. All rights reserved

BlockChain: A distributed solution to automotive security and privacy

Interconnected smart vehicles offer a range of sophisticated services that benefit the vehicle owners, transport authorities, car manufacturers and other service providers. This potentially exposes smart vehicles to a range of security and privacy threats such as location tracking or remote hijacking of the vehicle. In this article, we argue that BlockChain (BC), a disruptive technology that has found many applications from cryptocurrencies to smart contracts, is a potential solution to these challenges. We propose a BC-based architecture to protect the privacy of the users and to increase the security of the vehicular ecosystem. Wireless remote software updates and other emerging services such as dynamic vehicle insurance fees, are used to illustrate the efficacy of the proposed security architecture. We also qualitatively argue the resilience of the architecture against common security attacks