Performance evaluation of the Over-The-Air activation procedure in a large scale LoRaWAN

LoRaWAN is a promising LPWAN technology for IoT connectivity. It offers long-range and wide-area communication at low-power, low cost and low data rate. LoRaWAN performance has been evaluated according to many features such as coverage, scalability, physical layer parameters, communication reliability and latency. Existing studies assume that the LoRaWAN end-devices are already connected to the LoRa NetServer. Therefore, the performance of LoRaWAN activation procedure has not been well investigated. In this work, we study the performance of LoRaWAN during the Over-The-Air activation procedure. This process enables a large number of end-devices to join the network before being able to exchange any kind of packets. Thus, we analyze the average activation delay and the average energy consumption for an end-device in a large scale LoRaWAN. To achieve this goal, we first implement the Over-The-Air activation procedure in ns-3, especially in the ’lorawan’ module and conduct extensive simulations. Then, we elaborate a mathematical model using Markov-chain to evaluate both the delay and the energy consumption analytically. Our study shows that in a LoRaWAN cell composed of 1000 end-devices, the average activation delay for an end-device is about 35 minutes and this activation requires an average of three join-packet transmissions and an average energy consumption of 0.0887J.

     

RadiaLE: A framework for designing and assessing link quality estimators in wireless sensor networks

Stringent cost and energy constraints impose the use of low-cost and low-power radio transceivers in large-scale wireless sensor networks (WSNs). This fact, together with the harsh characteristics of the physical environment, requires a rigorous WSN design. Mechanisms for WSN deployment and topology control, MAC and routing, resource and mobility management, greatly depend on reliable link quality estimators (LQEs). This paper describes the RadiaLE framework, which enables the experimental assessment, design and optimization of LQEs. RadiaLE comprises (i) the hardware components of the WSN testbed and (ii) a software tool for setting-up and controlling the experiments, automating link measurements gathering through packets-statistics collection, and analyzing the collected data, allowing for LQEs evaluation. We also propose a methodology that allows (i) to properly set different types of links and different types of traffic, (ii) to collect rich link measurements, and (iii) to validate LQEs using a holistic and unified approach. To demonstrate the validity and usefulness of RadiaLE, we present two case studies: the characterization of low-power links and a comparison between six representative LQEs. We also extend the second study for evaluating the accuracy of the TOSSIM 2 channel model.     

Occurrence of Textile Dyes and Metals in Tunisian Textile Dyeing Effluent: Effects on Oxidative Stress Status and Histological Changes in Balb/c Mice

Although it is known that textile wastewater contains highly toxic contaminants whose effects in humans represent public health problems in several countries, studies involving mammal species are scarce. This study was aimed to evaluate the toxicity profile of 90-days oral administration of textile dyeing effluent (TDE) on oxidative stress status and histological changes of male mice. The TDE was collected from the textile plant of Monastir, Tunisia and evaluated for the metals, aromatic amines, and textile dyes using analytical approaches. Metal analysis by ICP-MS showed that the tested TDE exhibited very high levels of Cr, As, and Sr, which exceeded the wastewater emission limits prescribed by WHO and Tunisian authority. The screening of TDE through UPLC-MS/MS confirmed the presence of two textile dyes: a triphenylmethane dye (Crystal violet) and a disperse azo dye (Disperse yellow 3). Exposure to TDE significantly altered the malondialdehyde (MDA), Conjugated dienes (CDs), Sulfhydryl proteins (SHP) and catalase levels in the hepatic and renal tissues. Furthermore, histopathology observation showed that hepatocellular and renal lesions were induced by TDE exposure. The present study concluded that TDE may involve induction of oxidative stress which ensues in pathological lesions in several vital organs suggesting its high toxicity. Metals and textile dyes may be associated with the observed toxicological effects of the TDE. These pollutants, which may have seeped into surrounding rivers in Monastir city, can cause severe health malaise in wildlife and humans.     

Securely outsourcing the ciphertext-policy attribute-based encryption

Attribute-based Encryption (ABE) is a new and promising public key encryption that allows fine-grained authorization on data based on user attributes. Such property is favorable for multiple applications that require encrypted storage or access control on data, in particular: eHealth applications. However, ABE schemes are known not to be efficient in the encryption phase because ciphertext size and the time required to encrypt grow with the complexity of the access policy. Such drawback is critical in the context of pervasive computing, for instance, in the Internet of Things, where data producers are usually resource-constrained devices, e.g. smart phones or sensing platforms. In this work, we propose OEABE standing for Outsourcing mechanism for the Encryption of Ciphertext-Policy ABE (CP-ABE). We show how a user can offload expensive operations of CP-ABE encryption to a semi-trusted party in a secure manner. Our proposed mechanism requires only one exponentiation on resource-constrained devices. We provide also an informal security analysis of possible attacks from a semi-honest adversary against the proposed solution. To demonstrate the performance gains of our mechanism, we first conducted a performance estimation on an emulated Wismote sensor platform. Then, we implemented our proposal and did comparison to an existing implementation of CP-ABE on a laptop.     

Interfacial characteristics of poly(ε-caprolactone)-grafted-halloysites nanotubes bionanocomposites

Dielectric and thermal characterization of nanohybrid films based on poly(ε-caprolactone) biopolymer were investigated. Nano-composites samples with distinct loadings of halloysite nanotubes (HNT) were prepared by in situ Ring Opening Polymerisation of ε-caprolactone. The effect of the incorporated HNT on the molecular relaxation process and interfacial polarization of PCL was studied via broadband dielectric spectroscopy (BDS) on a frequency domain starting from 1E-1 to 1E6 Hz and at temperatures ranging from −70°C to 50°C. The BDS measurements revealed four significant dielectric processes α-primary relaxation attributed to glass transition, β-secondary relaxation and two interfacial polarizations due to the semi-crystalline character of PCL and the added HNT fillers. According to our results, the weight ratio of HNT ranging between 3% and 5% is recommended for achieving the highest performing nanocomposite that can be used in several applications.     

Charge and non-radiative energy transfer in P3HT-CdSe nanocomposite

A theoretical model based on the rate equation is used in the calculation of the light intensity and the exciton density profile. Interesting numerical results have been presented for low and high concentration of CdSe nanoparticles. We have found that the significant reduction of the electroluminescence intensity is related to the exciton density profiles which exhibit a monotonic decrease with the increase of the Förster energy transfer between host polymer (donor) and guest CdSe nanoparticles (acceptors). Moreover our calculations were found to be in good agreement with the experimental data.     

Electrochemical microstructured reactors: design and application in organic synthesis

The use of micro structured reactors is an accepted technology in fundamental chemical research as well as in industrial applications. The application of electrochemical microreactors (ECMR) has not attracted as much attention as continuously performed reactions in a confined space. Nevertheless ECMRs are in use to perform electro-organic reactions. In this review, different aspects of ECMRs with structured electrodes and interelectrode distances of mainly ≤100 μm are investigated and discussed, together with various manufacturing techniques and prototypes described therein. Based on representative examples described in various publications for electrolysis (for direct and indirect electrolysis) advantages and disadvantages of electrochemical microreactors are presented and compared with those of conventional electrochemical reactors.     

Oxidation kinetics of 4-methylanisole in methanol solution at carbon electrodes

A quantitative investigation of the electrochemical oxidation of 4-methylanisole in methanol solution at carbon electrodes has been performed. The oxidation reaction is shown to be complex, resulting in the formation not only of the corresponding diacetal, but also of several intermediate products and side products. Voltammetric measurements and preparative batch syntheses reveal a substantial influence of the choice of both electrode material and supporting electrolyte. The highest selectivity and the most rapid reaction rates are observed at graphite electrodes with potassium fluoride supporting electrolyte, whereas polished surfaces of glassy carbon are far less reactive and result in substantial formation of side products. The observed oxidation kinetics can be represented with a simple empirical model, consisting of three oxidation steps in series yielding respectively an ether, an acetal and an ester. The experimental voltammetric curves have been used to determine the anisole diffusivity in the electrolyte solution and provide fitted values for the kinetic parameters of the three oxidation steps.     

Potent Triple Helix Stabilization by 5′,3′‐Modified Triplex‐Forming Oligonucleotides

Anthraquinone and pyrene analogues attached to the 3′ and/or 5′ termini of triplex‐forming oligonucleotides (TFOs) by various linkers increased the stability of parallel triple helices. The modifications are simple to synthesize and can be introduced during standard solid‐phase oligonucleotide synthesis. Potent triplex stability was achieved by using doubly modified TFOs, which in the most favourable cases gave an increase in melting temperature of 30 °C over the unmodified counterparts and maintained their selectivity for the correct target duplex. Such TFOs can produce triplexes with melting temperatures of 40 °C at pH 7 even though they do not contain any triplexstabilizing base analogues. These studies have implications for the design of triplex‐forming oligonucleotides for use in biology and nanotechnology.     

Design and Performance Analysis of Objective Functions for RPL Routing Protocol

Wireless Personal Communications - Standardized by Internet Engineering Task Force (IETF) working group, RPL (Routing Protocol for Low Power and Lossy networks) stands as an effective IPV6 Routing...