Dynamic Clustering with Relay Nodes (DCRN): A Clustering Technique to Maximize Stability in Wireless Sensor Networks with Relay Nodes

With the growing popularity of wireless sensor networks, network stability has become a key area of current research. Different applications of wireless sensor networks demand stable sensing, coverage, and connectivity throughout their operational periods. In some cases, the death of just a single sensor node might disrupt the stability of the entire network. Therefore, a number of techniques have been proposed to improve the network stability. Clustering is one of the most commonly used techniques in this regard. Most clustering techniques assume the presence of high power sensor nodes called relay nodes and implicitly assume that these relay nodes serve as cluster heads in the network. This assumption may lead to faulty network behavior when any of the relay nodes becomes unavailable to its followers. Moreover, relay node based clustering techniques do not address the heterogeneity of sensor nodes in terms of their residual energies, which frequently occur during the operation of a network. To address these two issues, we present a novel clustering technique, Dynamic Clustering with Relay Nodes (DCRN), by considering the heterogeneity in residual battery capacity and by removing the assumption that relay nodes always serve as cluster-heads. We use an essence of the underlying mechanism of LEACH (Low-Energy Adaptive Clustering Hierarchy), which is one of the most popular clustering solutions for wireless sensor networks. In our work, we present four heuristics to increase network stability periods in terms of the time elapsed before the death of the first node in the network. Based on the proposed heuristics, we devise an algorithm for DCRN and formulate a mathematical model for its long-term rate of energy consumption. Further, we calculate the optimal percentage of relay nodes from our mathematical model. Finally, we verify the efficiency of DCRN and correctness of the mathematical model by exhaustive simulation results. Our simulation results reveal that DCRN enhances the network stability period by a significant margin in comparison to LEACH and its best-known variant.

Influence of Ni substitution on structural,morphological,dielectric,magnetic and optical properties of Cu-Zn ferrite by double sintering sol–gel technique

Polycrystalline NiCuZn ferrite(Ni_(x)Cu_(0.3)Zn(0.7-x)Fe_(2)O_(4);x=0.2,0.3,0.4 and 0.5)were prepared through solgel auto combustion method applying double sintering technique.Structural,morphological,elemental analyses(EDS),Fourier-transform infrared spectroscopy(FTIR),Direct Current(DC)electrical resistivity,dielectric,magnetic and optical properties of prepared samples were analyzed.XRD profiles reveal the formation of simple cubic spinel structure without any traceable impurity.The average crystallite size lies within the range of 22–29 nm.Lattice parameter decreases with increasing Ni concentration.Room temperature DC resistivity was recorded from 6:39×10^(5)to 3:79×10^(5)Ωcm.Both dielectric constant(ε)and loss factor(tanδ)were decreased with increase of frequency while AC conductivity increases.FTIR absorption peak occurred at three different frequency ranges at 570-577 cm^(-1),1635-1662 cm^(-1)and 3439–3448 cm^(-1).Magnetic properties were investigated by using vibrating sample magnetometer(VSM).Decreasing trends were observed for saturation magnetization(Ms),magnetic coercivity(Hc)and remanant magnetization(Mr)with the increase of Ni content.Optical band gap(-2.70-2.79 eV)were calculated from diffuse reflectance data by using Kubelka–Munk function.

Effect of sintering temperature on structural,magnetic,dielectric and optical properties of Ni-Mn-Zn ferrites

Spinel ferrite Ni_(0.08)Mn_(0.90)Zn_(0.02)Fe_(2)O_(4)was prepared by a conventional ceramic process followed by sintering at three different temperatures(1050°C,1100°C and 1150°C).X-ray diffraction(XRD)investigations stated the single-phase cubic spinel structure and the FTIR spectra revealed two prominent bands within the wavenumber region from 600 cm^(−1)to 400 cm^(−1).Surface morphol-ogy showed highly crystalline grain development with sizes ranging from 0.27μm to 0.88μm.The magnetic hysteresis curve at ambient temperature revealed a significant effect of sintering temperature on both coercivity(Hc)and saturation magnetization(Ms).Temperature caused a decrease in DC electrical resistivity,while the electron transport increased,suggesting the semicon-ducting nature of all samples and that they well followed the Arrhenius law from which their activation energies were determined.The values of Curie temperature(Tc)and activation energy were influenced by the sintering temperature.Frequency-dependent dielectric behavior(100 Hz-1 MHz)was also analyzed,which may be interpreted by the Maxwell-Wagner-type polarization.The UV-vis-NIR reflectance curve was analyzed to calculate the bandgap of ferrites,which showed a decreasing trend with increasing sintering temperature.

Synthesis,structural investigation,dielectric and magnetic properties of Zn^(2+)-doped cobalt ferrite by the sol-gel technique

Zinc substituted cobalt ferrite nanoparticles with elemental composition Co_(1-x)Zn_(x)Fe_(2)O_(4)(x=0.0,0.2,0.4,0.6)were prepared by the sol-gel auto-combustion technique using Co,Fe,Zn nitrate as a precursor where nitrates to citrate was 1:3.The as prepared powder of cobalt zinc ferrite was sintered at 900○C for 3 h.Structural,morphological,dielectric and magnetic properties were studied by x-ray diffractometer(XRD),scanning electron microscope(SEM),high precision impedance analyzer and vibrating sample magnetometer(VSM),respectively.The peaks obtained from the XRD confirmed samples having crystallite(32–36 nm)single phase inverse spinel structure without any traceable impurity.Lattice parameters were calculated from XRD and it increases with Zn content.SEM revealed irregularly shaped grains(-0.5–0.7μm)morphology with heterogeneous distribution.The dielectric constant(ε′)and dielectric loss(tanδ),have been measured as a function of frequency at room temperature.The dependence of ε′ and tan δ with frequency showed the normal dielectric behavior in accordance with the Maxwell-Wagner type of interfacial polarization and electron hopping change between Co^(2+)and Co^(3+)as well as between Fe^(2+)and Fe^(3+)ions at octahedral sites.