Sharif Digital Repository

A highly controllable, green, and rapid strategy is demonstrated for fabricating of highly sensitive non-enzymatic glucose sensing platforms. Carbon nanohorns (CNHs) were decorated onto the screen-printed electrodes. Binary nickel-cobalt sulfide (NiCo-S) nanosheets (NSs) were then deposited on CNH-casted electrodes by a facile and scalable method. Following detailed structural characterization and the electrocatalytic activity of the fabricated NiCo-S/CNH electrodes towards electro-oxidation of glucose was examined in detail. The proposed electrodes operated within two distinct linear dynamic ranges of 0.001- 0.330 mM and 0.330 - 4.53 mM with sensitivities of 1842 µA.mM−1.cm−2 and 854... 

The ever-expanding growth of internet traffic enforces deployment of massive Data Center Networks (DCNs) supporting high performance communications. Optical switching is being studied as a promising approach to fulfill the surging requirements of large scale data centers. The tree-based optical topology limits the scalability of the interconnected network due to the limitations in the port count of optical switches and the lack of optical buffers. Alternatively, buffer-less Fast Optical Switch (FOS) was proposed to realize the nanosecond switching of optical DCNs. Although FOSs provide nanosecond optical switching, they still suffer from port count limitations to scale the DCN. To address... 

Although hematite (i.e., α-Fe2O3) has been widely investigated in photoelectrochemical water oxidation studies due to its high theoretical photocurrent density, it still suffers from serious surface charge recombination and low photoelectrochemical stability. Here we report an in situ electrochemical method to form a uniform and ultrathin (i.e., 3-5 nm) passivation layer all over the pores of an optimized ∼3.2% Ti-doped α-Fe2O3 photoanode. We unveil the amorphous and defective nature of the in situ derived layer assigned to a high concentration of oxygen vacancies and intercalated potassium atoms there, i.e., the formation of Ti/K co-doped defective α-Fe2O3−x. Owing to the efficient... 

Network reliability measures the probability that a target node is reachable from a source node in an uncertain graph, i.e., a graph where every edge is associated with a probability of existence. In this paper, we investigate the novel and fundamental problem of adding a small number of edges in the uncertain network for maximizing the reliability between a given pair of nodes. We study the mathbf {NP}NP-hardness and the approximation hardness of our problem, and design effective, scalable solutions. Furthermore, we consider extended versions of our problem (e.g., multiple source and target nodes can be provided as input) to support and demonstrate a wider family of queries and... 

In recent years, community Q&A websites have attracted many users and have become reliable sources among experts from various fields. These platforms have specific rules to maintain their content quality in addition to general user agreements. Due to the vast expanse of these systems in terms of the number of users and posts, manual checking and verification of new contents by the administrators and official moderators are not feasible, and these systems require scalable solutions. In major Q&A networks, the current strategy is to use crowdsourcing with reliance on reporting systems. This strategy has serious problems, including the slow handling of violations, the loss of new and... 

Sharding, i.e. splitting the miners or validators to form and run several subchains in parallel, is known as one of the main solutions to the scalability problems of blockchains. The drawback is that as the number of miners expanding each subchain becomes small, it becomes vulnerable to security attacks. To solve this problem, a framework, named as Ployshard, has been proposed in which each validator verifies a coded combination of the blocks introduced by different subchains, thus helping to protect the security of all subchains. In this paper, we introduce an attack on Ployshard, called the discrepancy attack, which is the result of malicious nodes controlling a few subchains and... 

Network function virtualization (NFV) and software-defined networking (SDN) are two promising technologies to enable 5G and 6G services and achieve cost reduction, network scalability, and deployment flexibility. However, migration to full SDN/NFV networks in order to serve these services is a time-consuming process and costly for mobile operators. This paper focuses on energy efficiency during the transition of mobile core networks (MCN) to full SDN/NFV networks and explores how energy efficiency can be addressed during such migration. We propose a general system model containing a combination of legacy nodes and links, in addition to newly introduced NFV and SDN nodes. We refer to this... 

This paper investigates the performance of epidemic routing in mobile social networks considering several communities which are frequently visited by nodes. To this end, a monolithic Stochastic Reward Net (SRN) is proposed to evaluate the delivery delay and the average number of transmissions under epidemic routing by considering skewed location visiting preferences. This model is not scalable enough, in terms of the number of nodes and frequently visited locations. In order to achieve higher scalability, the folding technique is applied to the monolithic model, and an approximate folded SRN is proposed to evaluate performance of epidemic routing. Discrete-event simulation is used to... 

The Social Internet of Things (SIoT), integration of the Internet of Things and Social Networks paradigms, has been introduced to build a network of smart nodes that are capable of establishing social links. In order to deal with misbehaving service provider nodes, service requestor nodes must evaluate their trustworthiness levels. In this paper, we propose a novel trust management mechanism in the SIoT to predict the most reliable service providers for each service requestor, which leads to reduce the risk of being exposed to malicious nodes. We model the SIoT with a flexible bipartite graph, then build a social network among the service requestor nodes, using the Hellinger distance.... 

The Social Internet of Things (SIoT), integration of the Internet of Things and Social Networks paradigms, has been introduced to build a network of smart nodes that are capable of establishing social links. In order to deal with misbehaving service provider nodes, service requestor nodes must evaluate their trustworthiness levels. In this paper, we propose a novel trust management mechanism in the SIoT to predict the most reliable service providers for each service requestor, which leads to reduce the risk of being exposed to malicious nodes. We model the SIoT with a flexible bipartite graph, then build a social network among the service requestor nodes, using the Hellinger distance.... 

With the development of cloud computing, many enterprises have been interested in outsourcing their data to cloud servers to decrease IT costs and rise capabilities of provided services. To afford confidentiality and fine-grained data access control, attribute-based encryption (ABE) was proposed and used in several cloud storage systems. However, scalability and flexibility in key delegation and user revocation mechanisms are primary issues in ABE systems. In this paper, we introduce the concept of a fully distributed revocable ciphertext-policy hierarchical ABE (FDR-CP-HABE) and design the first FDR-CP-HABE scheme. Our scheme offers a high level of flexibility and scalability in the key... 

Dynamic Random Access Memory (DRAM) has been the leading main memory technology during the last four decades. In deep submicron regime, however, scaling DRAM comes with several challenges caused by charge leakage and imprecise charge placement. Phase Change Memory (PCM) technology is known as one of the most promising technologies to replace DRAM. Compared to competitive non-volatile memories like NAND Flash, Spin Transfer Torque random-access memory (STT-RAM), Magnetoresistive random-access memory (MRAM), PCM benefits from best attributes of fast random access, negligible leakage energy, superior scalability, high density, and operating in both Single-level Cell (SLC) and Multilevel Cell... 

The sequential deposition method is introduced for suppressing the leakage current in silicone rubber insulators. Room temperature vulcanizing silicone and TiO2/silica nanocomposites are sequentially deposited on silicone insulators surface. TEM results showed that TiO2 nanoparticles size is about 20–30 nm, and the structural study revealed their anatase crystalline structure. Silica nanoparticles are deposited on the surface of insulators by spray deposition. The contact angle was enhanced from 104° to 149° after nanoparticles deposition, which confirms the hydrophobicity improvement. Results show that leakage current for nanocomposite samples in a contaminated environment reduced to about... 

With recent considerable developments in the Internet of Things (IoT), billions of resource-constrained devices are interconnected through the Internet. Monitoring this huge number of IoT devices which are heterogeneous in terms of underlying communication protocols and data format is challenging. The majority of existing IoT device monitoring solutions heavily rely on centralized architectures. Since using centralized architectures comes at the expense of trusting an authority, it has several inherent drawbacks, including vulnerability to security attacks, lack of data privacy, and unauthorized data manipulation. Hence, a new decentralized approach is crucial to remedy these drawbacks. One... 

Hydrogen evolution through photoelectrochemical (PEC) water splitting by tungsten oxide-based photoanodes, as a stable and environmental-friendly material with moderate band gap, has attracted significant interest in recent years. The performance of WO3 photoanode could be hindered by its poor oxygen evolution reaction kinetics and high charge carrier recombination rate. Additionally, scalable and cost-effective commercial procedure to prepare nanostructured electrodes is still challenging. We present, for the first time, a novel and scalable method to fabricate highly efficient self-supported WO3/W nanostructured photoanodes from commercial W–Cu powder metallurgy (P/M) parts for water... 

This paper investigates the performance of epidemic routing, in mobile social networks (MSNs), which makes use of the store-carry-forward paradigm for communication. Real-life mobility traces show that people have skewed location visiting preferences, with some places visited frequently and some others infrequently. In order to model epidemic routing in MSNs, we first analyze the time taken for a node to meet the first node belonging to a set of nodes restricted to move in a specific subarea. Afterwards, a monolithic stochastic reward net (SRN) is proposed to evaluate the delivery delay and the average number of transmissions under epidemic routing by considering skewed location visiting... 

Data center performance is affected by three main factors; bandwidth, latency, and reliability of intra-data center interconnection network. Bandwidth and latency are definitely improved by adopting optical technology for intra-data center communication, but fault tolerance of the corresponding optical networks has been raised less. Recently, we introduced two Torus-based, all-optical, and non-blocking networks, i.e. O-TF and O-FTF, addressing reliability of optical networks, and now, in this paper, to address the scalability problem, we propose a novel Optical Clos-based architecture which reduces minimum number of required wavelength channels, as well as, the switch size in each node.... 

In some applicable scenarios, such as community patrolling, mobile nodes are restricted to move only in their own communities. Exploiting the meetings of the nodes within the same community and the nodes within the neighboring communities, a delay tolerant network (DTN) can provide communication between any two nodes. In this paper, two analytical models based on stochastic reward nets (SRNs) are proposed to evaluate the performance of the epidemic content retrieval in such multi-community DTNs. Performance measures computed by the proposed models are the average retrieval delay and the average number of transmissions. The monolithic SRN model proposed in the first step is not scalable, in... 

Electrochemical exfoliation of graphite has recently attracted a big attention as a simple, fast and scalable method for the preparation of high quality graphene, but there are some drawbacks that hinder its application. Direct deposition is one of the most critical challenges that makes it difficult to deposit uniform, compact and large scale graphene thin films. This work develops a facile electrophoretic deposition route to fabricate exfoliated graphene (EG) film on Ag nanowires (NWs) networks with a controllable film thickness in nanometers scale. EG thin films are deposited with different applied potentials and times from an EG dispersion in N, N-dimethylformamide solvent. Since... 

As technology process node scales down, on-chip SRAM caches lose their efficiency because of their low scalability, high leakage power, and increasing rate of soft errors. Among emerging memory technologies, Spin-Transfer Torque Magnetic RAM (STT-MRAM) is known as the most promising replacement for SRAM-based cache memories. The main advantages of STT-MRAM are its non-volatility, near-zero leakage power, higher density, soft-error immunity, and higher scalability. Despite these advantages, high error rate in STT-MRAM cells due to retention failure, write failure, and read disturbance threatens the reliability of cache memories built upon STT-MRAM technology. The error rate is significantly...