LSTR: Lightweight and Secure Tree-Based Routing for Wireless Sensor Networks

Wireless Personal Communications - This paper proposes a Lightweight and Secure Tree-based Routing protocol (LSTR) for Wireless Sensor Networks. The security of data routing from sensor nodes to...     

Characterization of the thermal behavior of PN thermoelectric couples by scanning thermal microscope

In this paper, we present the temperature profile measurements of a PN thermoelectric couple. The study is made in the AC regime. A couple is fed by a sinusoidal current and, using a scanning thermal microscope (SThM) and a lock-in scheme, we measure the amplitude and the phase of the first harmonic of the temperature along the surface of the couple. The influence of frequency is observed and we present a model which predicts the thermal behavior of the couple. The results of this model are in excellent agreement with the measurements.     

Fatty Acids in Heterocyclic Synthesis. Part XIV: Synthesis of Surface Active Agents from Some Novel Class of Oxadiazole,Thiadiazole and Triazole Derivatives Having Microbiological Activities

Reaction of stearic acid with semicarbazide in refluxing POCl₃ afforded 2-amino-5-heptadecyl 1,3,4-oxadiazole. Acylation of the amino group with acetic anhydride, ethyl chloroacetate and chloroacetic acid gave amide and β-amino acid derivatives. These compounds were cyclized to imidazo[2,1-b]oxadiazole derivatives by two different techniques. Treating the starting oxadiazole compound with P₂S₅, hydroxyl amine and hydrazine hydrate in benzene afforded thiadiazole and triazole derivatives. Unexpectedly, triazolo[3,4-b][1,3,4]oxadiazole derivative was obtained when 1,3,4-oxadiazole derivative was refluxed with hydrazine hydrate in ethanol. The biological activities of the synthesized compounds were screened in vitro against some gram positive and gram negative bacteria and fungi. Addition of quantitative amount of propylene oxide units (3, 5, 7 mol) to the synthesized compounds afforded new nonionic surfactants. The physico-chemical and surface properties of the novel synthesized surfactants such as surface and interfacial tension, cloud point, wetting time, emulsion stability, foam height, CMC, resistance to hydrolysis and their biodegradability were investigated. In addition, surface parameters including effectiveness (π _CMC), efficiency (PC₂₀), maximum surface excess (Γ_max) and (A _min) were examined.     

Intercalation of halloysite from Djebel Debagh (Algeria) and adsorption of copper ions

Halloysite available in Djebel Debagh, Guelma (eastern region of Algeria) was characterised by XRF, SEM, XRD, FTIR and by CEC, specific surface area and electrokinetic measurements. The crude halloysite was modified with Mⁿ⁺(CH₃COO)_n (M = Na⁺, NH₄⁺ or Pb²⁺), and intercalation of NaCH₃COO was monitored with time. XRD showed that the intercalation rate exceeded 90% for NaCH₃COO at long reaction time. X-ray diffraction also showed an expansion of the interlamellar space of 5.5 and 6.3 Å due to the intercalation of Pb(CH₃COO)₂ and NH₄CH₃COO. FTIR proved that Mⁿ⁺(CH₃COO)_n reacted with the inner surface hydroxyl groups of halloysite, on the basis of disappearance of the frequence bands at 3676 and 3652 cm^− 1 and the appearance of new bands around 3699 and 3457 cm^− 1. Intercalation of Pb(CH₃COO)₂ and NH₄CH₃COO shifted the band at 1650 towards 1663 and 1671 cm^− 1, respectively. The untreated and intercalated halloysite samples were used for removing copper(II) ions from aqueous solutions. The adsorption isotherms were of L-type according to the classification of Giles et al. (Giles, C.H., Mac Ewan, T.H., Makhwa, S.N., Smith, D., 1960. Studies in adsorption. Part XI. A system of classification of solution adsorption isotherms and its use in diagnosis of adsorption mechanisms and in measurement of specific surface areas of solids. J. Colloid Interface Sci. 3, 3973–3993.). The adsorption of copper ions was explained by electrostatic interaction between the copper(II) ions and negatively charged binding sites on halloysite surface and ion-exchange of the cations associated with acetate within the interlayer space.     

The rheological modelling of carbon nanotube (CNT) suspensions in steady shear flows

This paper is concerned with the rheological modelling of both chemically treated and untreated carbon nanotube (CNT) suspended in a Newtonian epoxy resin. CNT suspensions generally exhibited shear-thinning characteristic—the apparent viscosity decreases as shear rate increases—when subject to steady shear flows. Chemically treated CNT suspensions with little optical microstructure were found to exhibit a less significant shear-thinning effect compared with untreated CNT suspensions where clear optical aggregates were observed. In the case of treated CNT suspensions, the shear-thinning characteristic could be described using a Fokker–Planck based orientation model. The model assumed that the treated CNTs behaved as high aspect ratio rods and that shear flow was able to align the CNTs in the flow direction, thereby resulting in a decrease in the shear viscosity. Despite the success in describing the rheological response of treated CNT in steady shear flows, the orientation model failed to explain the more pronounced shear-thinning effect observed in untreated CNT suspensions having a hierarchy of aggregate structures. A new model called the aggregation/orientation (AO) model was formulated by modifying the Fokker–Planck equation. The AO model considered elements of aggregation as well as CNT orientation and it was capable of capturing the steady shear response of untreated CNT suspensions.