Lei Zhang

Bio: Lei Zhang is an academic researcher from University of Glasgow. The author has contributed to research in topics: Orthogonal frequency-division multiplexing & Communication channel. The author has an hindex of 36, co-authored 328 publications receiving 4743 citations. Previous affiliations of Lei Zhang include Huawei & Heriot-Watt University.

When Internet of Things Meets Blockchain: Challenges in Distributed Consensus

Abstract: Blockchain has been regarded as a promising technology for IoT, since it provides significant solutions for decentralized networks that can address trust and security concerns, high maintenance cost problems, and so on. The decentralization provided by blockchain can be largely attributed to the use of a consensus mechanism, which enables peer-to-peer trading in a distributed manner without the involvement of any third party. This article starts by introducing the basic concept of blockchain and illustrating why a consensus mechanism plays an indispensable role in a blockchain enabled IoT system. Then we discuss the main ideas of two famous consensus mechanisms, PoW and PoS, and list their limitations in IoT. Next, two mainstream DAG based consensus mechanisms, the Tangle and Hashgraph, are reviewed to show why DAG consensus is more suitable for IoT system than PoW and PoS. Potential issues and challenges of DAG based consensus mechanisms to be addressed in the future are discussed in the last section.

Blockchain-Enabled Wireless Internet of Things: Performance Analysis and Optimal Communication Node Deployment

Abstract: Blockchain has shown a great potential in Internet of Things (IoT) ecosystems for establishing trust and consensus mechanisms without involvement of any third party. Understanding the relationship between communication and blockchain as well as the performance constraints posing on the counterparts can facilitate designing a dedicated blockchain-enabled IoT systems. In this paper, we establish an analytical model for the blockchain-enabled wireless IoT system. By considering spatio-temporal domain Poisson distribution, i.e., node geographical distribution in spatial domain and transaction arrival rate in time domain are both modeled as Poisson point process (PPP), we first derive the distribution of signal-to-interference-plus-noise ratio (SINR), blockchain transaction successful rate as well as overall throughput. Based on the system model and performance analysis, we design an algorithm to determine the optimal full function node deployment for blockchain system under the criterion of maximizing transaction throughput. Finally, the security performance is analyzed in the proposed networks with three typical attacks. Solutions such as physical layer security are presented and discussed to keep the system secure under these attacks. Numerical results validate the accuracy of our theoretical analysis and optimal node deployment algorithm.

Synergistic Cocatalytic Effect of Carbon Nanodots and Co3 O4 Nanoclusters for the Photoelectrochemical Water Oxidation on Hematite.

Abstract: Cocatalysis plays an important role in enhancing the activity of semiconductor photocatalysts for solar water splitting. Compared to a single cocatalyst configuration, a cocatalytic system consisting of multiple components with different functions may realize outstanding enhancement through their interactions, yet limited research has been reported. Herein we describe the synergistic cocatalytic effect between carbon nanodots (CDots) and Co3O4, which promotes the photoelectrochemical water oxidation activity of the Fe2O3 photoanode with a 60 mV cathodically shifted onset potential. The C/Co3O4-Fe2O3 photoanode exhibits a photocurrent density of 1.48 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode), 78 % higher than that of the bare Fe2O3 photoanode. The slow reaction process on the single CoIII-OH site of the Co3O4 cocatalyst, oxidizing H2O to H2O2 with two photogenerated holes, could be accelerated by the timely H2O2 oxidation to O2 catalyzed on CDots.

Three-dimensional graphene-based aerogels prepared by a self-assembly process and its excellent catalytic and absorbing performance

Abstract: A simple one-step method for fabricating graphene-based hydrogels (GHs) with interconnected 3D networks using Cu nanoparticles was developed. During this process, graphene oxide (GO) was reduced by Cu nanoparticles to form reduced GO (rGO) which then self-assembled to form GHs. Meanwhile, the Cu nanoparticles were oxidized to form copper(I) oxide which deposited onto the rGO sheets and became imbedded in the GHs. The GHs were transformed to graphene-based aerogels (GAs) by a green freeze-drying method. The composition of the GAs can be easily adjusted by simply changing the initial amount of Cu nanoparticles or the concentration of the GO suspension. The GAs not only possess good catalytic performance for the catalytic reduction of 4-nitrophenol and the photocatalytic degradation of methyl orange but also have excellent capacities for removing various oils and dyes from water.

Enabling Massive IoT in 5G and Beyond Systems: PHY Radio Frame Design Considerations

Abstract: The parameters of physical layer radio frame for 5th generation (5G) mobile cellular systems are expected to be flexibly configured to cope with diverse requirements of different scenarios and services. This paper presents a frame structure and design, which is specifically targeting Internet of Things (IoT) provision in 5G wireless communication systems. We design a suitable radio numerology to support the typical characteristics, that is, massive connection density and small and bursty packet transmissions with the constraint of low-cost and low complexity operation of IoT devices. We also elaborate on the design of parameters for random access channel enabling massive connection requests by IoT devices to support the required connection density. The proposed design is validated by link level simulation results to show that the proposed numerology can cope with transceiver imperfections and channel impairments. Furthermore, the results are also presented to show the impact of different values of guard band on system performance using different subcarrier spacing sizes for data and random access channels, which show the effectiveness of the selected waveform and guard bandwidth. Finally, we present system-level simulation results that validate the proposed design under realistic cell deployments and inter-cell interference conditions.

Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study

Abstract: Summary Background Since December, 2019, Wuhan, China, has experienced an outbreak of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Epidemiological and clinical characteristics of patients with COVID-19 have been reported but risk factors for mortality and a detailed clinical course of illness, including viral shedding, have not been well described. Methods In this retrospective, multicentre cohort study, we included all adult inpatients (≥18 years old) with laboratory-confirmed COVID-19 from Jinyintan Hospital and Wuhan Pulmonary Hospital (Wuhan, China) who had been discharged or had died by Jan 31, 2020. Demographic, clinical, treatment, and laboratory data, including serial samples for viral RNA detection, were extracted from electronic medical records and compared between survivors and non-survivors. We used univariable and multivariable logistic regression methods to explore the risk factors associated with in-hospital death. Findings 191 patients (135 from Jinyintan Hospital and 56 from Wuhan Pulmonary Hospital) were included in this study, of whom 137 were discharged and 54 died in hospital. 91 (48%) patients had a comorbidity, with hypertension being the most common (58 [30%] patients), followed by diabetes (36 [19%] patients) and coronary heart disease (15 [8%] patients). Multivariable regression showed increasing odds of in-hospital death associated with older age (odds ratio 1·10, 95% CI 1·03–1·17, per year increase; p=0·0043), higher Sequential Organ Failure Assessment (SOFA) score (5·65, 2·61–12·23; p Interpretation The potential risk factors of older age, high SOFA score, and d-dimer greater than 1 μg/mL could help clinicians to identify patients with poor prognosis at an early stage. Prolonged viral shedding provides the rationale for a strategy of isolation of infected patients and optimal antiviral interventions in the future. Funding Chinese Academy of Medical Sciences Innovation Fund for Medical Sciences; National Science Grant for Distinguished Young Scholars; National Key Research and Development Program of China; The Beijing Science and Technology Project; and Major Projects of National Science and Technology on New Drug Creation and Development.

Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures.

Abstract: and Applications of Fullerenes, Carbon Dots, Nanotubes, Graphene, Nanodiamonds, and Combined Superstructures Vasilios Georgakilas,† Jason A. Perman,‡ Jiri Tucek,‡ and Radek Zboril*,‡ †Material Science Department, University of Patras, 26504 Rio Patras, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic

Challenges in reduction of dinitrogen by proton and electron transfer

Abstract: Ammonia is an important nutrient for the growth of plants. In industry, ammonia is produced by the energy expensive Haber–Bosch process where dihydrogen and dinitrogen form ammonia at a very high pressure and temperature. In principle one could also reduce dinitrogen upon addition of protons and electrons similar to the mechanism of ammonia production by nitrogenases. Recently, major breakthroughs have taken place in our understanding of biological fixation of dinitrogen, of molecular model systems that can reduce dinitrogen, and in the electrochemical reduction of dinitrogen at heterogeneous surfaces. Yet for efficient reduction of dinitrogen with protons and electrons major hurdles still have to be overcome. In this tutorial review we give an overview of the different catalytic systems, highlight the recent breakthroughs, pinpoint common grounds and discuss the bottlenecks and challenges in catalytic reduction of dinitrogen.

Development of MOF-Derived Carbon-Based Nanomaterials for Efficient Catalysis

Abstract: Carbon-based nanomaterials have been widely used as catalysts or catalyst supports in the chemical industry or for energy or environmental applications due to their fascinating properties. High surface areas, tunable porosity, and functionalization are considered to be crucial to enhance the catalytic performance of carbon-based materials. Recently, the newly emerging metal–organic frameworks (MOFs) built from metal ions and polyfunctional organic ligands have proved to be promising self-sacrificing templates and precursors for preparing various carbon-based nanomaterials, benefiting from their high BET surface areas, abundant metal/organic species, large pore volumes, and extraordinary tunability of structures and compositions. In comparison with other carbon-based catalysts, MOF-derived carbon-based nanomaterials have great advantages in terms of tailorable morphologies and hierarchical porosity and easy functionalization with other heteroatoms and metal/metal oxides, which make them highly efficient as...

A review of graphene and graphene oxide sponge: material synthesis and applications to energy and the environment

Abstract: This paper gives a comprehensive review about the most recent progress in synthesis, characterization, fundamental understanding, and the performance of graphene and graphene oxide sponges. Practical applications are considered including use in composite materials, as the electrode materials for electrochemical sensors, as absorbers for both gases and liquids, and as electrode materials for devices involved in electrochemical energy storage and conversion. Several advantages of both graphene and graphene oxide sponges such as three dimensional graphene networks, high surface area, high electro/thermo conductivities, high chemical/electrochemical stability, high flexibility and elasticity, and extremely high surface hydrophobicity are emphasized. To facilitate further research and development, the technical challenges are discussed, and several future research directions are also suggested in this paper.