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We prepared magnetite nano-hollow spheres with diameter 100–725 nm using solvothermal method. We studied the magnetic domain structures of the spheres and found them to vary from single domain for smaller diameter to multi-domain structure for the spheres of larger diameter. We also reported the frequency dependence of their magnetic properties and interestingly, found a systematic power law variation in coercivity and hysteresis loss with frequency, magnetic field strength and also with hollow sphere diameter. The results clearly represent that the domain wall width or the number of domains depends not only on the sphere diameter but also on the applied field frequency.

The present paper deals with the nonlinear finite element analysis of elastic water tanks. Both fluid and tank walls are discretized and modeled by two dimensional eight-node isoperimetric elements. In the governing equations, displacement for tank walls and pressure for the fluid domain are considered as independent nodal variables. The nonlinear term for the convective acceleration in Navier–Stokes equations is incorporated in the present analysis. The nonlinearity effects of the fluid are studied considering excitations both harmonic of various frequencies and random. The hydrodynamic pressure on tank wall is presented both from linear and nonlinear analysis for a comparison. The results show that the convective nonlinearity increases the magnitude of hydrodynamic pressure to a considerable amount when the excitation frequency approaches to the fundamental frequency of the water tank. The magnitude of hydrodynamic pressure in nonlinear analysis is quite large compare to that in linear analysis when the distance between the two vertical walls are relatively closer. However, the increase in pressure is insignificant when the tank is vibrated with a frequency higher than the frequency of the fluid domain. The seismic analysis results show that the distribution of nonlinear hydrodynamic pressure is almost similar to the linear pressure due to ground excitation.

Here, we report the synthesis of TiO2/BiFeO3 nanoheterostructure (NH) arrays by anchoring BiFeO3 (BFO) nanoparticles on TiO2 nanotube surface and investigate their pseudocapacitive and photoelectrochemical properties considering their applications in green energy fields. The unique TiO2/BFO NHs have been demonstrated both as energy conversion and storage materials. The capacitive behavior of the NHs has been found to be significantly higher than that of the pristine TiO2 NTs, which is mainly due to the anchoring of redox active BFO nanoparticles. A specific capacitance of about 440 F g–1 has been achieved for this NHs at a current density of 1.1 A g–1 with ∼80% capacity retention at a current density of 2.5 A g–1. The NHs also exhibit high energy and power performance (energy density of 46.5 Wh kg–1 and power density of 1.2 kW kg–1 at a current density of 2.5 A g–1) with moderate cycling stability (92% capacity retention after 1200 cycles). Photoelectrochemical investigation reveals that the photocurrent ...

Herein, we have performed rational surface modification of CoFe2O4 nanoparticles (NPs) to tune its room temperature ferrimagnetic properties by using different non-ionic surfactants. The NPs have been prepared by surfactant-assisted chemical co-precipitation technique with a narrow size distribution. For our study, we have chosen four non-ionic surfactants of triton X and tween group having different chain-lengths. Interestingly, we have found that surfactant co-ordinated magnetic NPs show a maximum of ~94% increase in coercivity along with a considerable decrease in magnetization as compared to the bare one. Systematic investigation reveals that both the nature and number of surfactant׳s head group and chain-length of its alkyl tail group have a remarkable impact on the magnetic properties of CoFe2O4 NPs. We believe that the tuned magnetic response of CoFe2O4 NPs depending on the nature of the surface binding ligand would open up many new opportunities as well as enhance their beneficial activities toward diverse application fields.

Composites of ferroelectric and magnetostrictive materials show more magnetoelectric coupling than single phase materials. Core–shell CoFe 2 O 4 :BaTiO 3 nanocomposites (1:1 weight ratio) and a mixture of both of them have been synthesized by a combination of hydrothermal and sol gel techniques. X ray diffraction analysis confirms the presence of both the materials in the samples. High Resolution Transmission Electron Microscope images confirm the core shell structure. The magnetoelectric coupling effect is investigated by measuring the magnetoelectric coefficient. It is observed that the coefficient is 35 times larger in the core–shell nanocomposites compared to that of the mixture.

Optimal operation of distribution systems plays an important role in the successful economic and secure operation of modern-day power systems under deregulated environment. Reduction in distribution loss and enhancement of bus voltage profile is often considered as the key parameters for economic and secure operation for distribution systems. Various methods including both mathematical and methods based on soft computing techniques have been utilized to address these problems. As reported in the literature, success of any heuristic technique greatly depends on the determination of optimal values of control parameters. Unfortunately, no analytical and straightforward method is available for the purpose. Usually, these parameters are selected experimentally considering different combination each time. A new hybrid algorithm using differential evolution and chaos theory is presented in the present work. Tent map chaotic sequence is utilized for self-adaptation of control parameters. The method is referred as tent map differential evolution (TMDE) in this work. The proposed hybrid algorithm is tested on 33-bus radial distribution system for validation and demonstration purpose. Systematic simulation results are presented and compared with same obtained by other modern techniques. It has been observed that it is capable of producing higher quality solution.

Co3O4 as a multifunctional nanomaterial, possessing simultaneously, unique optical, magnetic, and catalytic properties is sparse in the existing literature. We have activated intrinsic multicolor fluorescence covering the entire visible region by the functionalization of Co3O4 nanocubes (NCs) with Na-tartrate. The functionalized Co3O4 NCs show excellent catalytic efficiency in the degradation of both biologically and environmentally harmful dyes, which opens up a way for the possible application of the NCs toward therapeutic and wastewater treatment. Systematic investigations using UV-visible absorption, steady state, and time-resolved photoluminescence studies reveal the mechanistic origin behind the generation of multicolor fluorescence from the ligand-functionalized Co3O4 NCs. Moreover, from the magnetic study we have found that the room temperature antiferromagnetic nature of Co3O4 NCs turns to ferromagnetic after ligand functionalization due to the surface modification of the NCs. We believe that the developed multifunctional Co3O4 NCs could open up a new horizon toward their diverse applications in the present era of multitasking.

Distribution system is one of the important parts of power transfer systems. Large amount of power losses take place in the distribution system. Many modern heuristic techniques have been successfully applied over the years to solve the problem. Satisfactory performance of evolutionary algorithms like differential evolution is highly dependent on the setting of control parameters. One of the major difficulties for them is the selection of parameters which usually depend on specific problem under consideration. Sometimes, wrongly selected parameters may lead to premature convergence or even stagnation. It has been found that self-adaptation is a viable alternative option in setting control parameters. In this paper, a new hybrid optimization algorithm based on differential evolution and chaos theory called logistic map differential evolution (LMDE) is presented for minimization of loss and cost of distribution networks. Enhancement of voltage profile is also considered. The motivation behind the present work is to get rid of early convergence. To validate and demonstrate the effectiveness of the proposed method, a sample test system is considered. The simulation results clearly show that it can successfully avoid premature convergence. A comparison result is also presented which shows the capability of the proposed technique.

Economic load dispatch is one of fundamental issues in optimal power system operation. Several classical and modern heuristic techniques have been used to solve the problem. A novel algorithm is presented in this paper for solving economic load dispatch problem using a recently introduced simple yet powerful optimization technique called Jaya algorithm (JA). Most of the modern heuristic techniques require setting of control parameters which are usually problem specific. Moreover, there is no specific rule for the selection of these user-defined control parameters for most of the heuristic techniques. A wrong parameter may even lead to premature convergence. One of the major advantages in the proposed algorithm is that it does not require any problem-dependent control parameters. The economic load dispatch (ELD) problem is formulated by considering prohibited zones, ramp rate limits, and transmission losses satisfying a set of equality and inequality constraints. The proposed algorithm is tested on a six-unit test system in order to verify its effectiveness and efficiency. The simulation results are compared with those obtained by modern heuristic techniques. The simulation results show that the proposed technique has the capability of producing comparable results.

This paper presents utilization of particle swarm optimization in solving combined economic emission dispatch (EED) problem. The economic emission dispatch is an important problem in power sector as it combines two major objectives viz., cost minimization and emission minimization while maintaining operational constraints. Several meta-heuristic techniques have been developed in recent times and have been applied on power dispatch problems. PSO is such a meta-heuristic technique where time-varying acceleration coefficients (TVAC) are incorporated and used in the EED problem in this work. Thus it addresses the techno-economic-environmental aspect of power system operation. Economic emission dispatch problem is first resolved using weighted sum method, and second trade-off curve between two objectives has been found, referred to as pareto front which traces solutions obtained by non-dominated approach of the problem. The formulation is implemented on IEEE 30 bus test system and outcome obtained validates effectiveness of this research work.

In recent time due to diminishing fossil fuel reserves and increasing social pressure in terms of environmental pollution, complex power system has no other option except to seek for another possibility of alternative energy to eliminate the environmental pollution. Solar energy accounts for the most of the renewable energy on earth. PV module is a particular procedure to accomplish the generation of electric power from solar radiation using semiconductor devices which exhibit photovoltaic effects. The concepts of a PV module and its characteristics have been studied. The P–V and V–I curves have been obtained at changing solar irradiation levels and temperatures.

The effective utilization of abundant visible solar light for photoelectrochemical water splitting is a green approach for energy harvesting, to reduce the enormous rise of carbon content in the atmosphere. Here, a novel efficient design strategy for p-n type nano-heterojunction photoanodes is demonstrated, with the goal of improving water splitting efficiency by growing low band gap p-CuFeO

Optimal reactive power scheduling is one of the most complex and challenging problems in modern power system operation. This has recently gained intense attention from the scientist and researchers all over the world due to the introduction of liberalization or deregulation of electricity industry where reactive power is being traded as an ancillary service. This paper proposes an improved algorithm for optimal reactive power scheduling (ORPS) problem and a recently introduced simple yet powerful optimization technique called Jaya Algorithm (JA) is utilized for the same. The main advantage of the Jaya Algorithm is that it does not require any problem dependent control parameters. The optimal reactive power scheduling (ORPS) problem is formulated considering minimization of both losses and system cost satisfying several equality and inequality constraints. The algorithm described in this work is implemented on a standard test system for verifying its effectiveness and randomness. A comparison study of the simulation results is also performed with other modern heuristic techniques. The simulation results prove that it can produce acceptable results.

Integration of Distributed Generators (DG) in radial distribution system is one of the important and challenging works in the power system. Optimal allocation of DGs in the network system leads to the minimization of the overall distribution power loss as well as the improvement of the voltage profile. The main objective of this work is to minimize the total active power loss by strategically selecting the optimal sizes of DGs and its optimal locations in the system. Operating power factor of different types of DG may be different, so the power factor is also considered for the case studies. To minimize the objective function, opposition based chaotic differential evolution (OCDE) technique is used in this work. The proposed technique is tested on IEEE-33 bus and IEEE-69 bus radial distribution systems to verify the effectiveness of the proposed method. The results obtained by this technique are also compared with other techniques. It is observed that the proposed technique performs well for this type of problem.

Very recently, vacancy-type defects have been found to play a major role in stabilizing d0 ferromagnetism in various low dimensional ZnO systems. In this context, the evolution of vacancy-type defects within the ZnO nanocrystals due to the doping of ZnO by alkali metal lithium (Li) is investigated using X-ray photoelectron (XPS), photoluminescence (PL) and positron annihilation spectroscopy (PAS). Li-doping is found to have significant effects in modifying the vacancy-type defects, especially the Zn vacancy (VZn) defects within the ZnO lattice. XPS measurement indicated that initially the Li1+ ions substitute at Zn2+ sites, but when Li concentration exceeds 7 at%, excess Li starts to move through the interstitial sites. The increase in positron lifetime components and the lineshape S-parameter obtained from coincident Doppler broadening spectra with Li-doping indicated an enhancement of VZn defect concentration within the doped ZnO lattice. The vacancy type defects, initially of the predominant configuration VZn+O+Zn got reduced to neutral ZnO divacancies due to the partial recombination by the doped Li1+ ions but, when the doping concentration exceeded 7 at% and Li1+ ions started migrating to the interstitials, positron diffusion is partly impeded and this results in reduced probability of annihilation. PL spectra have shown intense green and yellow-orange emission due to the stabilization of a large number of VZn defects and Li substitutional (LiZn) defects respectively. Hence Li can be a very useful dopant in stabilizing and modifying significant amount of Zn vacancy-defects which can play a useful role in determining the material behavior.

Herein, we demonstrate the emergence of intrinsic multicolor fluorescence in α-Fe 2 O 3 nanoparticles (NPs) from blue, cyan, to green, upon functionalization and further surface modification with a small organic ligand, Na-tartrate. Furthermore, we have found an excellent photocatalytic property of the functionalized α-Fe 2 O 3 NPs in the decoloration of a model water contaminant. Detailed characterization of α-Fe 2 O 3 NPs before and after functionalization were carried out by X-ray diffraction and transmission electron microscopy. Proper investigation through UV-visible absorption and photoluminescence study along with theoretical support from literature reveals that ligand-to-metal charge transfer from tartrate ligand to lowest unoccupied energy level of Fe 3+ of the NPs and d-d transitions centered over Fe 3+ ions in the NPs play the key role in the generation of multiple fluorescence from the ligand functionalized α-Fe 2 O 3 NPs. Vibrating sample magnetometry measurements exhibit magnetic behavior of Fe 2 O 3 NPs changed considerably after surface modification. We believe that the developed ferromagnetic, multicolor fluorescent α-Fe 2 O 3 NPs would pioneer new opportunities toward diverse applications.

Ni-rich and Mn-rich Ni-Mn-Sn Heusler alloys have been prepared and studied to find out their magnetocaloric properties. The martensitic transition temperature decreases for Ni-rich and increases for Mn-rich alloys with the increase of their respective rich element. The value of isothermal magnetic entropy change is almost double for Mn-rich alloys as compared with the Ni-rich alloys. The refrigerant capacity is also higher for the same alloy series. The origin of such enhancement in magnetocaloric potentials in Mn-rich alloys has been discussed in the context of ferro/antiferro correlations present between the intersite Mn atoms of these alloy families.

The present article reports a facile method for preparing the vertically-aligned 1D arrays of a new type of type II n–n TiO2/ZnO core/shell nano-heterostructures by growing the nano-shell of ZnO on the electrochemically fabricated TiO2 nanotubes core for visible light driven photoelectrochemical applications. The strong interfacial interaction at the type II heterojunction leads to an effective interfacial charge separation and charge transport. The presence of various defects such as surface states, interface states and other defects in the nano-heterostructure enable it for improved visible light photoelectrochemical performance. The presence of such defects has also been confirmed by the UV-vis absorption, cathodoluminescence, and crystallographic studies. The TiO2/ZnO core/shell nano-heterostructures exhibit strong green luminescence due to the defect transitions. The TiO2/ZnO core/shell nano-heterostructures photo-electrode show significant enhancement of visible light absorption and it provides a photocurrent density of 0.7 mA cm−2 at 1 V vs. Ag/AgCl, which is almost 2.7 times that of the TiO2/ZnO core/shell nano-heterostructures under dark conditions. The electrochemical impedance spectroscopy results demonstrate that the substantially improved photoelectrochemical and photo-switching performance of the nano-heterostructures photoanode is because of the enhancement of interfacial charge transfer and the increase in the charge carrier density caused by the incorporation of the ZnO nano-shell on TiO2 nanotube core.

Arrays of permalloy nanowires (NWs) were fabricated into the pores of self-engineered Anodic Aluminium Oxide (AAO) templates by a simple electrodeposition technique (EDT) with a diameter -200 nm. By varying the length of the nanowires from 1.5 to 7.5 microm, got corresponding changes in aspect ratio from 7.5 to 37.5. We studied the growth and structural properties of permalloy nanowires using scanning electron microscopy, X-ray diffraction spectra and transmission electron microscopy. We performed the magnetic measurements of permalloy nanowires using vibrating sample magnetometer. The coercivity (H(c)) and anisotropy field (H(an)) observed considerably higher when the applied magnetic field was perpendicular to the nanowires axial direction (In-Plane) compare to the applied magnetic field was parallel to the nanowire axial direction (Out-of-plane). Reverse trend was observed for the maximum remanent ratio (M(r)/M(s)). So we concluded that the magnetic easy axis of the permalloy nanowires are along the axial direction of the nanowires and magnetic hardness of the nanowires higher in transverse direction compare to the axial direction of nanowires. For the first time temperature (80 K < or = T < or = 300 K) and aspect ratio dependence magnetic properties of the permalloy nanowires have been studied in detail.

Nickel rich Ni 52 Mn 34 Sn 14 Heusler alloy was prepared by arc melting and subsequent homogenization by annealing. Existence of first order magneto-structural transition (FOMST) was confirmed by various measurements. In comparison to conventional Ni 50− x Mn 36+ x Sn 14 alloys, a larger magnetic entropy change (∆ S M ≈8 J/kg K using Maxwell׳s thermodynamic equation and ∆ S M ≈18 J/kg K using Clasius–Clapeyron equation) and large negative magnetoresistance (MR≈−30%) were observed in the vicinity of martensitic transition temperature due to a change of 3 T and 8 T magnetic fields respectively. Effect of excess Ni content was discussed by considering other nearer compositions as reported by other researchers. Irreversibility in FOMST due to kinetic arrest was also studied from MR vs magnetic fields curves taken at a single temperature in two different initial phases. The exchange bias behavior in this alloy was studied by various magnetic measurements.

The MnFe2O4 nanoparticle has been among the most frequently chosen systems due to its diverse applications in the fields ranging from medical diagnostics to magnetic hyperthermia and site-specific drug delivery. Although numerous efforts have been directed in the synthesis of monodisperse MnFe2O4 nanocrystals, unfortunately, however, studies regarding the tuning of surface property of the synthesized nanocrystals through functionalization are sparse in the existing literature. Herein, we demonstrate the emergence of intrinsic multicolor fluorescence in MnFe2O4 nanoparticles from blue, cyan, and green to red, upon functionalization and further surface modification with a small organic ligand, Na-tartrate. Moreover, we have found an unprecedented photocatalytic property of the functionalized MnFe2O4 nanoparticles in the degradation of a model water contaminant. Detailed characterization through XRD, TEM, and FTIR confirms the very small size and functionalization of MnFe2O4 nanoparticles with a biocompatibl...

Nanostructured multiferroic Bi (1− x ) Ba x FeO 3 x =0.0, 0.1, 0.2 were prepared by hydrothermal technique. All samples belonged to the rhombohedrally distorted perovskite structure. The morphology of the particles changed with the doping of barium. Effect of barium doping on the dielectric constant was studied over a wide frequency range of 1000 Hz–1 MHz. The activation energy due to relaxation and due to conduction was measured from the Cole Cole plot and the AC conductivity versus frequency plot respectively. The activation energy estimated from both the studies was close to each other. The activation energy also enhanced with the increase in the barium content. The magnetization at the highest available field (~1.6 T) increased from 0.05 emu/g for the sample with x =0.0–12 emu/g for the sample with x =0.2. The magnetic measurements show a significant increase in magnetization around 400 °C. Remnant polarization for x =0.0 was negligible and it increased to 0.06 µC/cm 2 for x =0.2.

A plausible mechanism have been proposed here on the formation of chain like structure of Ni-Au-DNA (deoxyribo nucleic acid) composite which has been synthesized by simple wet-chemical process. The composite has been designed in such a fashion that it can be easily probed by optically, electrically and magnetically. In this paper, we are reporting its structural and physical properties in detail. Optical properties have been probed by Circular Dichroism (CD) which indicates no denaturization or melting of DNA even after formation of the composite structure. X-ray diffraction (XRD) study and Fourier transform infrared spectroscopy (FTIR) analysis show the nickel and gold are fcc in phase and bound to DNA through chemical bond, respectively. The composite shows room temperature semiconductor behavior. Temperature dependent magnetization and magnetic hysteresis loops are investigated in detail. The detail study of the composite indicates a possibility of its capability to be used in bio-devices. Furthermore, the tri-functionality of the composite will open-up its versatile applications.

In this article, we have investigated the effects of Li incorporation on the lattice defects and room-temperature d0 ferromagnetic behaviour in ZnO nanocrystals by correlating X-ray photoelectron, photoluminescence and positron annihilation spectroscopic study in details. It is found that at low doping level (

Here solvo-thermal technique has been used to synthesize hollow-nanospheres of magnetite. We have shown that PVP plays an important role to control the particle size and also helps the particles to take the shape of hollow spheres. Structural analysis was done by XRD measurement and morphological measurements like SEM and TEM were performed to confirm the hollow type spherical particles formation and their shape and sizes were also investigated. The detail ac-dc magnetic measurements give an idea about the application of these nano spheres for hyperthermia therapy and spontaneous dye adsorption properties (Gibbs free energy deltaG0 = -0.526 kJ/mol for Eosin and -1.832 kJ/mol for MB) of these particles indicate its use in dye manufacturing company. Being hollow in structure and magnetic in nature such materials will also be useful in other application fields like in drug delivery, arsenic and heavy metal removal by adsorption technique, magnetic separation etc.

Monodisperse, unagglomerated nanoparticles of CoFe2O4 were synthesized by a solvothermal technique using various capping agents. Three sets of particles were synthesized having size ∼7 nm, ∼14 nm and ∼23 nm. Detailed morphology study was done by X ray diffraction and High resolution Transmission Electron Microscope. Ac hysteresis loops of these samples were measured at room temperature within a frequency range of 50 Hz–600 Hz. We have reported the frequency dependence of coercivity and Specific absorption rate (SAR) and have found a very interesting result that the coercivity varies with different power of frequency for the particles of different size. Particles of sample A followed the Neel type of relaxation. The relaxation measurements were also done on all the samples to vindicate the occurrence of Neel type of relaxation. The SAR values and the fast relaxation proves that these particles can be utilized for hyperthermia treatment.

Multiferroic materials having good magneto-electric coupling are of great interest due to their enormous variety of applications in the field of spintronic devices. Despite having good magneto-electric coupling and multiferroic properties, gallium ferrite (GaFeO3) is plagued for having a very high leakage current compared to other multiferroic materials, which shadows the possibility of its application in device fabrication. The conduction mechanism behind this exceptionally high leakage current in GaFeO3 is still not identified properly. Here, we have carefully investigated the variation of leakage conduction with the change in morphologies, especially at the grain boundaries due to heat treatment temperature during sample preparation. A connected conductive network is detected along the fused grain boundaries, which provides the pathway for the leakage electrons to propagate through the material. Interestingly, the conductive atomic force microscopy image shows that oxygen vacancies at the near grain boundaries produce poor conductive regions. Small polaron hopping could be an effective transport mechanism present in the conductive ridges at the grain boundaries. Therefore, modification of grain boundaries could produce more effective results for the reduction in leakage current of GaFeO3.

Two dimensional (2D) arrays of CoxPt1−x alloy nanowires (NWs) with x = 0.75, 0.5, and 0.28 having wire diameter of ∼200 nm are synthesized in porous alumina membrane by electrodeposition technique. The as-deposited arrays of NWs show a distinct magnetic easy axis along their perpendicular direction with respect to the NWs axes. All the as-prepared NWs show low remanence (

The Ni 50 Mn 36.5 Sn 13.5 alloy was prepared and annealed for four different times (6, 12, 18 and 24 hrs) at 1173 K. The width of the martensitic transition (MT) was found to decrease with the increase of annealing time. The 24 hrs annealed sample showed a larger magnetic entropy change ( ΔS M ) near MT, but relatively narrower transition width limited its refrigerant capacity (RC) to a significant extent. The sample annealed for 12 hrs exhibited larger RC and indicated that the partially disordered Ni-Mn-Sn alloys can be a better magnetocaloric candidate as compared to the ordered one.

Structural and magnetic transitions of Ni48.5−xCoxMn37Sn14.5 (x = 0, 1 and 2) alloys were studied by thermal, electrical and magnetic measurements. The exchange bias was found to be present in all the samples below 120 K. Contrary to other Heusler alloys, no magnetic hysteresis was observed in the isothermal M–H curves for x = 0 sample at the first order magneto-structural transition. Large magnetic entropy change (ΔSM) ∼ 6.15, 10.36 and 9.85 J/kg K was obtained respectively for x = 0, 1 and 2 due to a change of only 1.5 T magnetic field. Incorporating hysteresis losses, refrigerant capacity was estimated to be 50, 74 and 54.7 J/kg for the same samples respectively.

1D porous ultrathin nanoribbons of hematite (α-Fe2O3) were prepared by controlled annealing of different oxides and hydroxides of iron obtained from a solvothermal synthesis method. It is found that calcination at a temperature of 500 °C for 150 min decomposes these iron hydroxides into their most stable oxide form, i.e., α-Fe2O3. Driven by different attractive forces, these porous α-Fe2O3 nanoparticles get aggregated in an ordered fashion to form an ultrathin 1D nanoribbon structure, as observed by detailed time dependent TEM and HRTEM analysis. It has been found that the high aspect ratio and porous surface morphology of these nanoribbons have significantly improved their electronic and spintronic properties as manifested by their photocatalysis, gas sensing, electrochemical, and magnetic behaviors. These hematite nanoribbons exhibit a weak ferromagnetic behavior due to surface spin disorder and shape anisotropy. Lateral confinement of electrons increases the band gap of the nanoribbons, as evident from the UV absorption analysis, which in turn improves their photocatalytic degradation efficiency (rate constant ∼0.95 h(-1)) by delaying the electron-hole recombination process. However, their liquid petroleum gas sensing properties have been found to be mainly governed by the improved (porous) surface of the hematite nanoribbons that provides huge interaction sites for the analyte gas. Most of all, these hematite nanoribbons show a significantly enhanced pseudocapacitive performance exhibited by their high specific capacitance of about 145 F g(-1) at a current density of 1 A g(-1), high rate capability, and also long cycle stability (nearly 96% of capacity retention after 1600 charging/discharging cycles).

We report the effect of the variation of diameter on the optical, magnetic, and magnetodielectric properties of the Pr–Cr-codoped BiFeO3 (BFO) nanowires (NWs). Pr–Cr-codoped BFO NWs with different diameters (18, 35, 55, 100, 150, and 250 nm) have been fabricated by employing a simple wet chemical template-assisted route. The effect of quantum confinement has been found to have a significant influence on the room-temperature photoluminescence and Raman spectra of the NWs. An interesting blue shift in the band gap emission is observed in the photoluminescence spectra of the NWs as a result of quantum confinement. The position and the intensity of the Raman peaks are found to change significantly depending on the variation in the NW diameter. The room-temperature ferromagnetism of the codoped BFO NWs increases consistently with the decrease in the diameter of the NWs because of the suppression of the spiral spin structure and the increase in the number of uncompensated for spins at the NW surface (as the sur...

A simple wet chemical technique has been employed to fabricate MnO2 nanolayer-coated α-Fe2O3/MnO2 core–shell nanowire heterostructure arrays to prepare unique pseudocapacitor electrodes. The coating of MnO2 on α-Fe2O3 nanowires is triggered by the reduction of KMnO4 solutions by the metallic (Au) film on which the polycrystalline α-Fe2O3 nanowires have been grown electrochemically. This metallic film also acts as the current collector by making direct contact with the arrays of the 1D nanoheterostructures. The as-prepared α-Fe2O3/MnO2 nanoheterostructures are found to exhibit excellent specific capacitance, high energy density, high power density, and long-term cyclic stability as compared with the bare α-Fe2O3 nanowire electrodes. The unique geometry of the 1D nanoheterostructures with high effective surface area to allow faster redox reaction kinetics, the incorporation of two highly redox active materials in the same structure, and the porous surface structures of the heterostructure to allow facile el...

The evolution of vacancy-type crystalline defects across the transition from anatase to rutile structure of titanium dioxide (TiO2) nanoparticles during high-temperature annealing in oxygen and argon is studied by using positron lifetime and coincidence Doppler broadening spectroscopic measurements. The TiO2 nanoparticles were synthesized through a simple sol–gel chemical route. The changes in the crystalline phase and lattice parameters of the nanoparticles upon thermal treatment were investigated by X-ray diffraction and high-resolution transmission electron microscopy, and the results were correlated with those of photoluminescence spectroscopy and positron annihilation measurements. The structural defects, mostly 3D vacancy clusters, in the nanoparticles were found to decrease in concentration during the annealing in O2 rather than in Ar at elevated temperatures. In the case of annealing in Ar, the vacancy-type defects persisted even at the highest annealing temperature of 900 °C used in the experimen...

Congestion management (CM) is one of the severe problems in deregulated or liberalized electricity industry. In a liberalized electricity market, transmission lines are normally operated near its rated capacity and sometimes, this may cause congestion in the lines. This is because every market participants have the intention to maximize their profits. Failure of managing congestion properly may ultimately lead to the system collapse. Several methods including both classical and modern heuristic techniques have been used to address the problems of congestion management with different level of success. A novel hybrid algorithm based on differential evolution and chaos theory is presented in the present paper to alleviate congestion in power systems by rescheduling of participating generators. The algorithm tested on a standard system to demonstrate its capability in alleviating congestion of power systems. A comparative result is also presented in the present work. It is observed that the present technique is capable in improving the quality of solutions.

Development of solar energy worldwide in the last ten years has brought into purview the maximum power point tracking and module mismatch losses. Such losses are mainly occurred by partial shading of the solar panel and various kinds of solar modules. These losses can be reduced by different parameter analysis. There are five various interconnected plans, which depict reasonably reliable power production prognosticate under normal operating condition. PV is the method of generating electric power conversion i.e. solar radiation into electrical power using semiconductor devices exhibiting the photovoltaic effects. The analysis of current over voltage and power over voltage characteristics at varying solar irradiation levels and temperatures has been obtained. In this study, a novel theoretical model, offering a good compromise between simplicity and accuracy, is developed using Matlab to determine the parametric study of different types of solar module /arrays to demonstrate a feasibility and reliability of the simulation model.

The origin of photoluminescence (PL) of the anodic aluminium oxide (AAO) membranes synthesized by electrochemical anodization of aluminium by using oxalic, phosphoric and sulfuric acid electrolytes for different anodization time duration have been investigated. All the as prepared AAO membranes exhibit strong visible blue luminescence around 410–430 nm at room temperature. The mechanism of the visible light emission in AAOs has been explained by correlating the structural studies of the membranes with the PL and electron paramagnetic resonance (EPR) spectroscopy measurements. It is found that the AAO membranes are amorphous in nature (XRD and HRTEM study) and they contain large concentration of structural of defects (HRTEM study). The extensive PL and EPR investigations have indicated the presence of singly ionized oxygen vacancy related defects (F + center defects) in AAO membranes. Based on the experimental evidences, the F + center defects are attributed to the visible blue light emission from the AAOs.

Au nanoparticle decorated α-Fe2O3 NWs exhibit enhanced band gap luminescence due to coupling between excitons in α-Fe2O3 NWs and the surface plasmons of Au particles. The enhanced magnetization in α-Fe2O3 NWs with Au coating is attributed to the interfacial effects arising from the trapped metallic electrons at the Au/α-Fe2O3 NWs interface.

Optimal reactive power planning is one of the most challenging problems in power system operation. Different techniques including classical and modern heuristic methods have been utilized to address the problem successfully. It is observed that success of heuristic techniques largely depends on the selection of some user defined control parameters. Multiple runs are required to find the optimal values of control parameters. Again these parameters are usually problem dependent. In other words, for different problems these parameters are to be selected separately. A wrong parameter selection may even lead to premature convergence. No specific rule is available for setting these parameters. A new improved hybrid algorithm for optimal reactive power planning (ORPP) problem using differential evolution combining with chaos theory is proposed in this paper. A self adaptive parameter automation strategy is adopted is this paper. For the present work, tent map chaotic sequence is used and the proposed technique is termed as tent map differential evolution (TMDE). Minimization of loss and system cost are taken into account in problem formulation. The proposed algorithm is applied on IEEE-30 bus system in order to verify its effectiveness and efficiency. A comparison result with other recent methods is presented which shows the capability of the proposed technique in producing good quality solutions.

This article demonstrates comprehensive studies on different visible-light driven photoelectrochemical and photocatalytic aspects of a hydrothermally synthesized n-type H

We report a facile method to design Co3O4–MnO2–NiO ternary hybrid 1D nanotube arrays for their application as active material for high-performance supercapacitor electrodes. This as-prepared novel supercapacitor electrode can store charge as high as ∼2020 C/g (equivalent specific capacitance ∼2525 F/g) for a potential window of 0.8 V and has long cycle stability (nearly 80% specific capacitance retains after successive 5700 charge/discharge cycles), significantly high Coulombic efficiency, and fast response time (∼0.17s). The remarkable electrochemical performance of this unique electrode material is the outcome of its enormous reaction platform provided by its special nanostructure morphology and conglomeration of the electrochemical properties of three highly redox active materials in a single unit.

Here we report the facile synthesis of 1D ZnO/α-Fe2O3 semiconductor nanoheterostructures (SNHs), and we investigate the strong interfacial interactions at the heterojunction, resulting in novel multifunctional properties. ZnO-coated α-Fe2O3 nanowires (NWs) have been prepared by combining electrodeposition and wet chemical methods. Significant improvement in electrical conductivity, photoluminescence, and room temperature magnetic properties have been observed for the ZnO/α-Fe2O3 SNHs over the pristine α-Fe2O3 NWs because of the contribution of the ZnO nanolayer. The increase in electrical conductivity in ZnO/α-Fe2O3 SNHs is because of the increase in free electrons in the conduction band of the SNHs due to the formation of type-II n-n band configuration at the heterojunction. The SNHs are found to exhibit enhanced visible green photoluminescence along with the UV emission at room temperature. The band-gap emission of the α-Fe2O3 NWs coupled to the defect emissions of the ZnO in SNHs can be attributed to t...

Room temperature magnetization of two dimensional (2D) arrays of cobalt nanowires (NWs) having diameter 50 and 150 nm prepared by electrodeposition are studied in details. Diffraction patterns of the NWs reveal that the crystallites of the NWs become more textured on decreasing their diameter. Magnetic hysteresis loop measurements show the magnetic easy axis changes its direction from axial to perpendicular direction of NWs on increasing the length of the NWs. The magnetostatic interaction among the NWs, known as the key factor in defining the easy direction is found not to be dipolar at all the circumstances. An aspect ratio (length/diameter of NWs) dependence of the non-dipolar interaction in 150 nm NWs is evident from the static magnetization as well as from ferromagnetic resonance (FMR) measurements.

Bi1–xBaxFeO3 (0.0≤x≤0.25) ceramics are prepared by chemical synthesis route. At room temperature, antiferromagnetic BiFeO3 is converted to ferromagnetic on doping Ba. A large change in the magnetization is observed around 370 °C which is close to the Neel temperature (TN) of parent compound. Another magnetic transition is also observed near 600 °C. Spin canting or impurity phase could be a probable reason for the origin of ferromagnetism in both cases. Ferroelectric and magnetic transitions of the compounds shift towards higher temperature with Ba-doping concentration. Anomaly in the dielectric constant is also observed near the TN of BiFeO3. The composition x=0.15 shows the maximum magnetic moment at room temperature while better fatigue resistance and maximum magnetoelectric coupling are observed for x=0.20 composition.

Highlights: Black-Right-Pointing-Pointer Rod shaped lanthanum doped bismuth ferrite was obtained. Black-Right-Pointing-Pointer The diameter of the particles were found to be decreasing on doping with lanthanum. Black-Right-Pointing-Pointer Both ferromagnetic and dielectric properties enhanced. Black-Right-Pointing-Pointer A transition due to spin canting is observed near 550 Degree-Sign C. Black-Right-Pointing-Pointer Electron spin resonance study shows the breakage of spin cycloid due to doping. -- Abstract: Cylindrical-shaped multiferroic Bi{sub 1-x}La{sub x}FeO{sub 3} (x = 0.0, 0.05, 0.1 and 0.15) were synthesized successfully by hydrothermal method. All samples were found to be rhombohedrally distorted perovskite structure. Diameter of the cylindrical particles reduces from {approx}450 nm for x = 0.0 to {approx}100 nm for x = 0.1 prepared under the same conditions. The Neel temperature as well as the dielectric constant was also found to increase with the increase in lanthanum content. Lanthanum doping also enhanced the magnetic properties. Magnetization measurements above room temperature show a significant increase in magnetization at around 400 Degree-Sign C. Enhanced magnetic properties due to lanthanum doping are caused by the breakage of spin cycloid as observed by electron spin resonance study.

The effects of rare-earth-element Gd doping on the intrinsic magnetic ordering, photoluminescence, and electrical-conducting properties of the pristine SnO(2) nanocrystalline thin films fabricated by radio-frequency (RF) sputtering are investigated. The pristine SnO(2) thin film exhibits significant ferromagnetism while Gd doping results in an absence of intrinsic ferromagnetism. The presence of large amounts of singly ionized oxygen vacancies (V(O)(+)) is traced by photoluminescence spectroscopic analysis and they are found to be responsible for the observed ferromagnetism in pristine SnO(2) thin films. A significant reduction of oxygen vacancies is observed after Gd doping, and that might be insufficient to mediate long-range ferromagnetic ordering between V(O)(+) defects in a Gd-doped SnO(2) system. Although the associated magnetic moment is increased by 1 order of magnitude, because of the insertion of Gd(3+) ions, which have localized f-shell paramagnetic moment, there is no intrinsic FM ordering. Hall measurement reveals that the pure SnO(2) exhibits n-type behavior whereas Gd-doped SnO(2) films show the p-type conductivity with higher resistivity. The studies demonstrate that only structural defects such as V(O)(+) defects, not magnetic ions such as Gd(3+), are responsible for inducing ferromagnetism in SnO(2) thin films.

Arrays of SnO 2 nanowires are fabricated by employing a wet chemical template assisted sol–gel route using ordered nanoporous anodic aluminium oxide as the host. The origin of room temperature d 0 ferromagnetism in pristine polycrystalline SnO 2 nanowires is investigated by correlating photoluminescence and electron paramagnetic resonance (EPR) studies. It has been found that the naturally grown structural defects of oxygen vacancies namely singly ionised oxygen vacancy ( V O ) clusters induce the characteristic photoluminescence and contribute in ferromagnetism of pristine SnO 2 nanowires at room temperature. The presence of the V O structural defects in the pure SnO 2 nanowires is also assured by the EPR spectroscopy. Present study will help understand the puzzle about the unexpected magnetic phenomenon in these undoped wide band gap oxide semiconductors.