Hydrolysis of Fe(OH)SO4 in the presence of metallic iron

Hydrolysis of Fe(OH)SO₄ was carried out in the presence of metallic iron in order to prevent the formation of iron(III) oxides with strongly bonded sulphate. Under the conditions of the experiment, the products were found to be mixtures of ?-Fe₂O₃ and α-FeOOH. The occluded sulphate, if any, could be easily washed out with water. The hydrolysis reaction passes through an equilibrium state before coming to completion. The entropy with enthalpy of the hydrolysis corresponding to the equilibrium state were found to be 4 e.u. and 0·5 kJ/mol, respectively. The activation energy of the hydrolysis reaction was found to be 21 kJ/mol.     

Social‐based reputation‐aware data forwarding for improved multicast delivery in the presence of selfish nodes in DTNs

Delay/disruption tolerant networks (DTNs) are potentially applicable in the challenged scenarios like post‐disaster environments. In such networks, data forwarding generally relies on the mutual cooperation of the nodes. However, in reality, despite the availability of necessary resources for data forwarding, a node could misbehave by dropping messages received from other nodes with whom it has no strong social ties. Such a node is called a socially selfish node, which would cause a poor delivery ratio in the network. In this paper, we aim to address the problem of multicast data forwarding in the presence of such selfish nodes, by means of efficient relay selection in DTNs. First, we define a realistic reputation model, in contrast to existing models, to define the socially selfish/misbehaving nodes in the network. Further, a game‐theoretic analysis is carried out that implies data forwarding cost is also an influential parameter in handling selfishness/misbehavior. Subsequently, the problem is formulated as a constrained optimization problem, which is NP hard. Therefore, a heuristic is proposed by combining the reputation of a node and the cost of message forwarding to appropriately identify relay nodes, thus improve the performance of the multicast message delivery in the network. We utilize a social metric, centrality to minimize the message forwarding cost in terms of the number of relay nodes. Finally, the comparative performance evaluation in ONE simulator with practical scenarios shows the superiority of the proposed scheme over the other prominent schemes.     

A heterostructured SnO2–TiO2 thin film prepared by Langmuir–Blodgett technique

SnO₂–TiO₂ heterostructure films were prepared through Langmuir–Blodgett (LB) route. LB films of octadecyl amine (ODA)–titanyl oxalate multilayer deposited on Si (100) and decomposed at 600 °C showed rutile and anatase phases of ultrathin TiO₂ film. Subsequently, multilayer LB film of ODA–stannate deposited on the pre deposited TiO₂ film after decomposition at 600 °C resulted in thin SnO₂ films on the TiO₂ thin film. The phase analysis of the SnO₂–TiO₂ film showed cassiterite phase of SnO₂ as well as the rutile/anatase mixture of TiO₂ indicating a SnO₂–TiO₂ heterostructured film. Surface morphology of the pure TiO₂ film and SnO₂–TiO₂ film were analyzed by using AFM. Electrical characterization by AC impedance analysis suggested SnO₂–TiO₂ heterostructure formation. DC current voltage measurement showed increase in photocurrent indicating visible light absorption and efficient charge separation under the sunlight type radiation.     

Fairness in message delivery in delay tolerant networks

Wireless Networks - Rare existence of the end-to-end path and intermittent connectivity among the nodes are the key characteristics of delay tolerant networks (DTNs). Such networks are potentially...     

Synthesis of Glutamic Acid Derived Organogels and their Applications in Dye Removal from Aqueous Medium

To develop glutamic acid derived cross‐linked polymeric organogels for dye adsorption from aqueous media, dimethyl 2‐(methacrylamido)pentanedioate (Glu‐MAC) is polymerized using diethylene glycol dimethacrylate as cross‐linker via the reversible addition‐fragmentation chain transfer (RAFT) technique to synthesize cross‐linked polymeric organogels with pendant glutamate moieties. The mechanical properties of organogels are examined by rheological study. The organogels exhibit higher value of storage modulus (G′) than the loss modulus (G′′) within the linearity limits of deformation, and strong dependence of G′ values on the extent of cross‐linking in the gel matrix. Field emission scanning electron microscopy shows porous structure of the gel matrix, therefore, organogels are able to exhibit swelling behaviors in organic solvents such as dichloromethane, N,N‐dimethylformamide, tetrahydrofuran, acetone, and methanol. Dye adsorption properties of these organogels are investigated using different aqueous dye solutions, such as crystal violet (CV), malachite green (MG), rhodamine‐B, and uranine. The gels show high dye adsorption capacities (≥97%) toward cationic dyes like CV and MG.     

LoWaNA: low overhead watermark based node authentication in WSN

Nodes in a wireless sensor network (WSN) are generally deployed in unattended environments making them susceptible to attacks. Therefore, the need of defending such attacks is of utmost importance. The challenge in providing security in this network is that the securing mechanism must be lightweight to make it implementable for such resource-constrained nodes. A robust security solution for such networks must facilitate authentication of sensor nodes. So far, only data authentication has drawn much attention from the research community. In this paper, a digital watermark based low-overhead solution (LoWaNA) is proposed for node authentication. The proposed watermarking technique consists of three modules viz. watermark generation, embedding and detection. The robustness of the algorithm is measured in terms of cracking probability and cracking time. This robustness analysis helps us to set the design guideline regarding size of watermark. Performance of the scheme is analyzed in terms of storage, computation and communication overhead. The analytical results are compared with two of the existing schemes and that show significant reduction of all such overheads. Thus it proves the suitability of the proposed scheme for resource-constrained networks like WSN. Finally the entire scheme is simulated in Cooja, the Contiki network simulator to make it readily implementable in real life mote e.g. MICAz.

     

Low-overhead video compression combining partial discrete cosine transform and compressed sensing in WMSNs

Wireless multimedia sensor network (WMSN) is a special wireless sensor network (WSN) made up of several multimedia sensor nodes, specially designed to retrieve multimedia content such as video and audio streams, still images, and scalar sensor data from the environment. Due to strict inherent limitations in terms of processing power, storage and bandwidth, data processing is a challenge in such network. Further, energy is one of the scarcest resources in WSN, especially in WMSN and therefore, saving energy is of utmost importance. Data compression is one of the solutions of such a problem. This paper proposes an energy saving video compression technique for WMSN by judicious combination of partial discrete cosine transform and compressed sensing. This amalgamation exploits the benefits of both the techniques towards fulfilling the objective of saving energy along with achieving desired peak signal to noise ratio (PSNR). When the transform technique ensures low-overhead compression, compressed sensing guarantees the reconstruction of the same video with lesser amount of measurements. Performance of the scheme is measured both qualitatively and quantitatively. In qualitative analysis, overhead of the scheme is measured in terms of storage, computation, and communication overheads and the results are compared with a number of existing schemes including the base scheme. The results show considerable reduction of all such overheads thereby justifying the appropriateness of the proposed scheme for resource-constrained networks like WMSNs. In quantitative analysis, for both ideal and packet loss environment, the scheme is simulated in Cooja, the Contiki network simulator to make it readily implementable in real life mote e.g. MICAz. When compared with the existing state-of-the-art schemes, it performs better not only in terms of 34.31% energy saving but also in getting an acceptable PSNR of 35–37 dB and SSIM of 0.85–0.88 in ideal environment. In packet loss environment, these values are 32.9–35.5 dB and 0.81–0.85 respectively implying acceptable reconstruction even in packet loss environment. Further, it requires the least storage of 51.2 KB. The observation on simulation results is also justified by statistical analysis.

     

A dynamic TDMA based scheme for securing query processing in WSN

Nodes in a wireless sensor network (WSN) are generally deployed in unattended environments making the nodes susceptible to attacks. Therefore, the need of defending such attacks becomes a big challenge. We propose a scheme to build a security mechanism in a query-processing paradigm within WSN. The scheme is capable of protecting replay attack while preserving essential properties of security such as authentication, data integrity and data freshness. The solution is made lightweight using symmetric key cryptography with very short-length key. Further, the key used in our scheme is neither pre-deployed nor is transmitted directly. The key information is established among nodes through an efficient use of one variant of dynamic TDMA mechanism which ensures security of key. Another variant of dynamic TDMA is used to make the scheme bandwidth saving, an essential quality of WSN. Performance of the scheme is analyzed in terms of storage, computation and communication overhead. Finally the analytical results are compared with two of the existing schemes including the previous version of the present scheme that show significant reduction of all such overheads thereby proving the suitability of the proposed scheme for a resource-constrained network like WSN.     

Studies on the formation of Langmuir monolayer and Langmuir–Blodgett films of octadecyl amine-bromocresol purple dye complex

Properties of the monolayer of octadecyl amine (ODA) molecules on aqueous solution of bromocresol purple (Bcp) dye have been studied over a wide range of pH by measuring the surface pressure-area isotherms. A strong interaction of ODA molecule was observed with the dye molecule in the pH range of 4–9. Under the present study, the dye molecules were adsorbed on the ODA monolayer at the water surface and subsequently a Langmuir–Blodgett (LB) film of ODA–dye complex was transferred from the air–water interface onto a solid substrate. Alternatively, dye molecules were incorporated into LB film by immersing the predeposited LB film of pure ODA into the dye solution, i.e. by adsorption of dye molecule at the solid–liquid interface. The adsorption behavior of ODA–Bcp dye complexes obtained through these two different routes was characterised with the help of UV–Visible spectroscopy. The nature of the ODA–dye complex deposited from air–water interface using the LB technique was found to be quite different from that of the complex formed by the adsorption of the dye into the pure ODA LB film. The adsorption spectra of the ODA–dye complex obtained from the air–water interface did not change with pH, while those of the ODA–dye complex formed from the solid–liquid interface showed pH dependence.     

Atmospheric Fine and Coarse Mode Aerosols at Different Environments of India and the Bay of Bengal During Winter-2014: Implications of a Coordinated Campaign

In this paper, we present mass concentrations of particulate matter [PM_2.5, PM₁₀ size fractions and total suspended particulates (TSP)] measured simultaneously over land stations (Kullu, Patiala, Delhi, Ajmer, Agra, Lucknow, Varanasi, Giridih, Kolkata, Darjeeling, Jorhat, Itanagar, Imphal, Bhubaneswar, and Kadapa), mostly distributed across the Indo-Gangetic plain (IGP) of India as well as in the marine atmosphere over Bay of Bengal (BoB) in the period from 20 January to 3 February, 2014. The main objective of this study was to quantify the continental outflow of particulates (PM_2.5, PM₁₀ and TSP) from IGP and associated regions into the BoB along with low level north-east wind flow during winter monsoon period. The present study provides a glimpse of the aerosol loading over the IGP region. During this campaign, the highest average PM_2.5 (187.8 ± 36.5 µg m^?3, range 125.6–256.2 µg m^?3), PM₁₀ (272.6 ± 102.9 µg m^?3, range 147.6–520.1 µg m^?3) and TSP (325.0 ± 71.5 µg m^?3, range 220.4–536.6 µg m^?3) mass concentrations were recorded at Varanasi, Kolkata and Lucknow over middle and lower IGP regions. The PM_2.5 (average 41.3 ± 11.9 µg m^?3; range 15.0–54.4 µg m^?3), PM₁₀ (average 53.9 ± 18.9 µg m^?3; range 30.1–82.1 µg m^?3) and TSP (average 78.8 ± 29.7 µg m^?3; range 49.1–184.5 µg m^?3) loading over BoB were found to be comparable to land stations and suggests possible continental outflow. Over the continental region, the highest PM_2.5/PM₁₀ ratio was recorded at Delhi (0.87). The PM_2.5/PM₁₀ ratio over BoB (0.77) was found to be quite high and comparable to Varanasi (0.80) and Agra (0.79).