We study price and lead time quotation decisions in a make-to-order system with two customer classes: (1) contract customers whose orders are practically always accepted and fulfilled based on a ...contract price and lead time agreed on at the beginning of the time horizon, and (2) spot purchasers who arrive over time and are quoted a price and lead time pair dynamically. The objective is to maximize the long-run expected average profit per unit time, where profit from a customer is defined as revenues minus lateness penalties incurred because of lead time violations. We model the dynamic quotation problem of the spot purchasers as an infinite horizon Markov decision process, given a fixed price and lead time for contract customers. We analyze the impact of customer preferences (e.g., price and lead time sensitivity) on the optimal price and lead time decisions for spot purchasers and characterize the optimal policy. We explore the benefits of dynamic quotation compared to the use of fixed price and lead times, and provide recommendations for firms. Finally, we analyze the optimal contract terms given the dynamic quotation strategy for spot purchasers and discuss the profit improvements offered by the optimal mix of spot and contract customers.
Display omitted
•The reduction of azo dyes and nitro compounds were instantly completed with MnFe2O4@SiO2@Ag MRCs.•MnFe2O4@SiO2@Ag MRCs was used as heterogeneous catalyst.•MnFe2O4@SiO2@Ag MRCs with ...the room-temperature magnetism showed that it could be used as a recyclable catalyst.•MnFe2O4@SiO2@Ag MRCs showed high catalytic activity both for studied azo dyes and nitro compounds.
In this study, magnetically recycable MnFe2O4@SiO2@Ag nanocatalyst (MnFe2O4@SiO2@Ag MRCs) has been synthesized through co-precipition and chemical reduction method. XRD analysis confirmed the synthesis of single phase nanoproduct with crystallite size of 10nm. VSM measurements showed the superparamagnetic property of the product. Catalytic studies showed that MnFe2O4@SiO2@Ag MRC could catalyze the reduction of the various azo compounds like methyl orange (MO), methylene blue (MB), eosin Y (EY), and rhodamine B (RhB) and also aromatic nitro compounds such as 4-nitrophenol (4-NP), 4-nitroaniline (4-NA) and 2-nitroaniline (2-NA). Moreover, the magnetic nanocatalyst showed an excellent reusability properties that remained unchanged after several cycles. Therefore, MnFe2O4@SiO2@Ag is the potential candidate for the application of organic pollutants for wastewater treatment.
•Series of spinel CoxMg1−xFe2O4 nano-catalysts synthesized by sol-gel method.•Samples were characterized by XRD, SEM, EDX, TEM, DRS, VSM techniques.•Structural phase formation shows cubic crystal ...planes.•Average crystallite size was calculated by Sherer formula found that 18.59–21.22 nm.•Optical energy-band shows increasing with dopant altering between 2.14 and 2.59 eV.
In this study, spinel magnesium cobalt ferrite (CoxMg1−xFe2O4: x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0) nanocomposites were synthesized successfully by modified sol-gel combustion method. Magnesium nitrate, cobalt nitrate and iron nitrate were used as the source of divalent (Mg2+ and Co2+) and trivalent (Fe3+) cations, respectively and urea were used as the reducing (fuel) agent. The effects of cobalt ions on morphology, structural, optical, magnetic and photo-catalytic properties of spinel CoxMg1−xFe2O4 nanocomposites were investigated. Various characterization methods, including X-ray powder diffraction (XRD), high resolution scanning electron microscope (HR-SEM), transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transforms infrared (FT-IR) spectroscopy, vibrating sample magnetometer (VSM) and photo-catalytic degradation (PCD) activity were used to study the phase purity, microstructure, particle size, elemental composition, functional group determination, band gap calculation, magnetic properties and degradation efficiency of nanoparticles, respectively. The observed results showed that the final products consists cubic spinel phase with sphere-like nanoparticles morphologies. Furthermore, spinel Co0.6Mg0.4Fe2O4 nanocomposite showed highest PCD efficiency (98.55%) than other composition of ferrite nanoparticles.
Strontium hexagonal ferrite, SrFe
12
O
19
, with platelet-like structure was synthesized directly by hydrothermal method without any calcination process. The product was characterized by Scanning ...electron (SEM), X-ray powder diffraction (XRD), Fouier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometry (VSM) techniques. The optimum Fe/Sr moler atio is identified as 8:1, and the optimum weight of NaOH was 4.0 g for the synthesis of the Flake-like SrFe
12
O
19
nanoparticles. The average crystallite size of the product was calculated as 28±5 nm. The low coercivities of the synthesized platelet crystals indicate soft magnetic behavior, which is a consequence of the large shape anisotropy (the platelet crystals are highly anisotropic). The reduced Ms can be explained by increasing surface area of the platelets.
•Nanosized M-type SrFe12−xVxO19 (0.00 ≤ x ≤ 0.1) hexaferrites have been synthesized via sol-gel auto-combustion method.•Lattice constant ‘c’ found to be increased with vanadium substitution.•The ...Vanadium substitutions weaken the magnetic properties of SrM hexaferrites.•The V3+ ions have the preference to occupy the 2a and 2b sites.
In the present study, the preparation of nanocrystalline strontium vanadium nanohexaferrites was undertaken using a sol-gel auto-combustion method. The structural and morphological properties were characterized using X-ray diffraction (XRD), Fourier transform infra-red (FT-IR) analysis, and scanning electron microscopy (SEM). The XRD analysis showed that the crystallite sizes (t) of the products vary between 55 and 60 nm, while the SEM analysis confirmed the hexagonal platelet structure of the products. The magnetic hysteresis loops indicated that the synthesized nanohexaferrites exhibit ferrimagnetic-like (FM) behavior. The deduced saturation (MS) and the remnant (Mr) magnetizations, the coercive (HC) and magneto-crystalline anisotropy (Ha) fields diminished as the V3+ content increased. The Ha values are very high, pointing to the hard FM characteristics of the synthesized nanohexaferrites. Except for x = 0.0, the squareness ratios, Mr/MS, are below 0.50, suggesting the presence of multi-domain nano-sized particles for SrFe12−xVxO19 (0.00 ≤ x ≤ 0.1) nanohexaferrites.
•Bi2Mo2O9 NPs were prepared by microwave combustion route.•Bi2Mo2O9 NPs were characterized by various techniques.•The EC properties were investigated by CV, GCD, and EIS.•The specific capacitance is ...197 F/g at 0.4 A/g with cycle stability of 94 %.•The results showed potential application for energy storage systems.
In this present work, bismuth molybdate (Bi2Mo2O9) nanoparticles (NPs) were prepared by microwave combustion method using urea as the fuel. The phase formation and purity of the product was identified by powder X-ray diffraction (XRD). Fourier transform-infrared (FT-IR) analysis was adopted to record the functional group of Bi2Mo2O9 NPs. The morphology, purity, size and elemental composition of the sample were confirmed by Scanning electron microscope (SEM), elemental mapping, energy dispersive X-ray (EDX) analysis and High-Resolution transmission electron microscope (HR-TEM) technique respectively. The UV–visible and photoluminescence (PL) spectra were used to examine optical and electronic behavior of the prepared sample at room temperature (RT). The chemical bonding of Bi2Mo2O9 NPs was studied by Raman spectroscopy. The magnetic properties of Bi2Mo2O9 NPs were examined by vibrating sample magnetometer (VSM) at RT. The particle size distribution was examined by X-ray Photoelectron spectroscopy (XPS). The Electrochemical (EC) properties of Bi2Mo2O9 NPs were investigated by Cyclic voltammetry (CV), Galvanostatic charge/discharge (GCD) and Electrochemical impedance spectral (EIS) studies. The specific capacitance (Cs) of prepared Bi2Mo2O9 NPs is 197 F/g at 0.4 A/g with excellent cycle stability of 94% specific capacitance after 1000 cycles. Hence, the results of electrochemical characteristics exhibits excellent performance and have potential application of electrode for energy storage systems.
•Rare earth element Ce3+ doped CoFe2O4 NPs were prepared by simple sol-gel combustion technique.•Cerium was successfully substituted into the spinel lattice without any distortion.•Powder XRD and SEM ...along with EDX studies confirmed the pure phase formation.•There was a substantial decrease in the crystallite size on doping with Ce3+.•Magnetic properties altered by the addition of Ce3+ in the CoFe2O4 matrix.
In this present study, we made an attempt for the different concentration of rare earth element (REE) Cerium (Ce3+) doped cobalt ferrite (CoFe2O4) nanoparticles (NPs) were prepared by the simple sol-gel combustion technique. Cerium was successfully substituted into the spinel lattice without any distortion. It was analyzed the effect of Ce3+ ions doping on structural, morphological, magnetic properties and antibacterial activities using the various instrument techniques. Powder XRD and SEM along with EDX studies confirmed the pure phase formation Ce3+ doped CoFe2O4 NPs and spherical shaped agglomerated nanoparticles morphology without any other impurity. The well resolved broad peaks in the XRD pattern clearly indicated the nanosized, single phased, cubic spinal nature of these samples. There was a substantial decrease in the crystallite size on doping with Ce3+. A more in-depth morphological study was facilitated using the TEM and SAED analysis. TEM investigation revealed random shaped, sharp edged nanoparticles with a normally facetted morphology. The presence of distinctive diffractions spots on the SAED pattern indicated the formation of nanoparticles that are highly crystalline in nature. The magnetic response of the Ce3+ doped CoFe2O4 NPs was recorded at room temperature (RT) using the VSM technique. The magnetic properties have been seen to be altered by the addition of Ce3+ in the CoFe2O4 matrix. The decrease in the saturation magnetization (Ms, emu/g) with the increase in Ce3+ content rendered the synthesized sample applicable in field of antenna construction. This change will be also suitable for reducing the size of the antenna. The antibacterial activity of Ce3+ doped CoFe2O4 nanoparticles was found to be enhanced with increase in Ce3+ doping level as it cause a reduction in the grain size.
We report in this investigation the preparation as well as characterization of bulk YBa2Cu3O7-δ superconductor produced by solid state reaction route and added by various amount (x) of CNTs (x = 0.0, ...0.1 and 1.0 wt%). The analysis of X-ray diffraction (XRD) indicated the achievement of orthorhombic structure of YBCO phase for various sintered samples. No relevant variations in the lattice parameters is observed with CNTs inclusion. The analysis of microstructure revealed a dispersion of CNTs into YBCO and presence of lattice defects for CNTs added samples. We evaluated the impacts of CNTs on inter-granular traits of YBCO using AC susceptibility measurements. Various superconducting parameter including critical temperature (Tc), inter-granular critical current density (Jc inter), grain volume fraction (fg), grains susceptibility (χg) and matrix susceptibility (χm) were estimated and deeply discussed. The obtained results confirm that the CNTs addition has a beneficial role on the inter-granular properties of YBCO system. Also, the critical current density Jcm was determined and its value has been shown to be greatly enhanced with the addition of CNTs in the existence of the applied magnetic field.
•YBa2Cu3O7-δ/(CNTs)x with 0.0 ≤ x ≤ 1.0 wt% were produced by solid-state reaction process.•Microstructural analysis revealed a dispersion of CNTs into YBCO.•Presence of lattice defects for CNTs added samples.•Highest critical current density was achieved with CNTs addition into YBCO superconductor.•CNTs addition has a beneficial role on the inter-granular properties of YBCO system.
Abstract
Indium-substituted strontium hexaferrites were prepared by the conventional solid-phase reaction method. Neutron diffraction patterns were obtained at room temperature and analyzed using the ...Rietveld methods. A linear dependence of the unit cell parameters is found. In
3+
cations are located mainly in octahedral positions of 4f
VI
and 12 k. The average crystallite size varies within 0.84–0.65 μm. With increasing substitution, the T
C
Curie temperature decreases monotonically down to ~ 520 K. ZFC and FC measurements showed a frustrated state. Upon substitution, the average and maximum sizes of ferrimagnetic clusters change in the opposite direction. The M
r
remanent magnetization decreases down to ~ 20.2 emu/g at room temperature. The M
s
spontaneous magnetization and the k
eff
effective magnetocrystalline anisotropy constant are determined. With increasing substitution, the maximum of the ε
/
real part of permittivity decreases in magnitude from ~ 3.3 to ~ 1.9 and shifts towards low frequencies from ~ 45.5 GHz to ~ 37.4 GHz. The maximum of the tg(α) dielectric loss tangent decreases from ~ 1.0 to ~ 0.7 and shifts towards low frequencies from ~ 40.6 GHz to ~ 37.3 GHz. The low-frequency maximum of the μ
/
real part of permeability decreases from ~ 1.8 to ~ 0.9 and slightly shifts towards high frequencies up to ~ 34.7 GHz. The maximum of the tg(δ) magnetic loss tangent decreases from ~ 0.7 to ~ 0.5 and shifts slightly towards low frequencies from ~ 40.5 GHz to ~ 37.7 GHz. The discussion of microwave properties is based on the saturation magnetization, natural ferromagnetic resonance and dielectric polarization types.
ABSTRACT
In this study, we examine the long-term torque noise fluctuations of persistent X-ray binaries Her X-1, Vela X-1, GX 301-2, Cen X-3, 4U 1538-53, OAO 1657-415, and 4U 1626-67 using the ...historical pulse frequency measurements provided by CGRO/BATSE and Fermi/GBM. We find that known disc-fed sources exhibit a 1/ω2 red noise component in their power density spectra which is saturated over long time-scales. On the other hand, wind-fed sources form a clear white noise component, and the wind-fed sources with occasional transient disc formation imprint 1/ω type flicker noise. We discuss their long-term timing noise properties based on the models to describe the power density spectrum of pulse frequency derivative fluctuations in terms of monochromatic and coloured noise processes. Furthermore, we investigate the relation between measured timing noise strengths and other independently measured physical parameters. Despite the low number of sample sources, we suggest that the noise strengths of these sources are correlated with their luminosities and uncorrelated with their magnetic field strengths, implying that the dominant noise-generating mechanism is accretion.
PDF
