This work presents the design techniques to synthesize a class of compact inline quasi-elliptic-type waveguide cavity bandpass filters based on novel nonlinear frequency-variant couplings (NFVCs). ...These highly dispersive frequency-variant couplings (FVCs) are realized by means of a pair of partial-height posts that are placed at the junctions between every two cavity resonators. Each NFVC produces a transmission pole in between a pair of independently adjustable transmission zeros (TZs). Although the pole is added to the overall filtering function to augment its order, the TZs can be placed at each side of the filter passband to attain sharp rejection capability and increase the stopband attenuation levels. To synthesize these filters, two coupling-routing-diagram (CRD) approaches for the NFVC are presented that either consider: 1) an arbitrary FVC (AFVC) or 2) two resonating nodes interacting with a zero-susceptance nonresonating node through constant inverters. An equivalent lumped-element circuit model associated with both CRD approaches is provided. It is demonstrated that both CRD models can be exploited for the theoretical synthesis of this type of filter, whereas the equivalent lumped-element circuit model can provide a deeper insight into the systematic dimensioning of the posts. For experimental validation purposes, three design examples are synthesized, and 10-GHz proof-of-concept filter prototypes of two of them are EM-simulated, fabricated, and characterized. The measured results agree well with the simulations and the design theory, thus verifying the concept of inline waveguide cavity filters with TZs using NFVCs.
In this work, a family of frequency-variant reactive coupling (FVRCAFVC) networks is introduced and discussed as new building blocks for the synthesis of coupled-resonator bandpass filters with real ...or complex transmission zeros (TZs). The FVRCAFVC is a type of nonideal frequency-dependent inverter that has nonzero elements on the diagonal of the impedance matrix, along with a nonlinear frequency-variation profile of its transimpedance parameter. The distinctive feature of these new FVRCsAFVC is that they can be modeled with a simple bridged-T network consisting of four reactive elements. Such FVRCsAFVCs can introduce one pole and up to two TZs-so that they are referred to as double-zero single-pole (DZSP) networks. DZSP networks allow the pole to be located above, below, or in-between the TZs. Depending on the choice of the elements in the bridged-T circuit, the position of the TZs and the pole can be controlled independently. The coupling matrix for filters with DZSP networks can be found by solving an inverse-structured nonlinear eigenvalue problem (ISNEVP). Examples of possible implementations of DZSP couplingAFVC networks are provided for both lumped and quasi-lumped-element circuits, as well as for transmission-line-based and waveguide technologies. The application of DZSP coupling networks to the design of microwave bandpass filters with generalized Chebyshev-type characteristics is illustrated by means of the synthesis of three microstrips and two waveguide coupled-resonator bandpass filters. The waveguide filters are verified through electromagnetic (EM) simulations and the microstrip filters are manufactured and characterized for proof-of-concept demonstration purposes, showing a fairly close agreement between EM simulations and measurements.
The cure models based on standard distributions like exponential, Weibull, lognormal, Gompertz, gamma, are often used to analyze survival data from cancer clinical trials with long-term survivors. ...Sometimes, the data is simple, and the standard cure models fit them very well, however, most often the data are complex and the standard cure models don't fit them reasonably well. In this article, we offer a novel generalized Gompertz promotion time cure model and illustrate its fitness to gastric cancer data by three different methods. The generalized Gompertz distribution is as simple as the generalized Weibull distribution and is not computationally as intensive as the generalized F distribution. One detailed real data application is provided for illustration and comparison purposes.
In this study, molecular imprinted polymer (MIP)-based impedimetric sensor has been developed to detect dengue infection at an early stage. Screen-printed carbon electrode (SPCE) was modified with ...electrospun nanofibers of polysulfone (PS) and then, coated with dopamine while using NS1 (non-structural protein 1—a specific and sensitive biomarker for dengue virus infection) as template during polymerization. The self-polymerization of dopamine at room temperature helps to retain exact structure of template (NS1) which results in generating geometrically fit imprinted sites for specific detection of target analyte. The electrochemical properties of MIP-modified SPCEs were studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) at every step of modification. Under optimal conditions, impedimetric measurements showed linear response in the range from 1 to 200 ng/mL. The developed sensor can selectively detect NS1 concentrations as low as 0.3 ng/mL. Moreover, impedimetric sensor system was also employed for NS1 determination in real human serum samples and satisfying recoveries varying from 95 to 97.14% were obtained with standard deviations of less than 5%.
Bimetallic Ag
(core)
/Au
(shell)
and Au
(core)
/Ag
(shell)
core-shell nanoparticles are synthesized in aqueous phase using simple citrate reduction method with variations for both sets in the ...reaction conditions during the fabrication of shell structure, i.e., change in salt concentration, temperature (from 25 to 100 °C), and pH for salt solutions (from 2 to 12). The surface plasmon resonance effect, size and morphology, elemental composition, crystalline structure, and crystallite size were observed for these bimetallic core-shell nanoparticles using techniques such as UV-Vis spectroscopy, SEM, EDX, and XRD respectively. The size observed for Ag
(core)
/Au
(shell)
nanoparticles was 50 ± 6 nm, and Au
(core)
/Ag
(shell)
nanoparticles was 64 ± 8 nm. Increasing the concentration of salt for Au or Ag shows better coating and increase in shell thickness as observed by surface plasmon resonance (SPR) peaks. At lower temperatures, generally, agglomeration occurs or in case of Au
(core)
/Ag
(shell)
nanoparticles, formation of Ag
3
O
4
occurs; however, at higher temperatures, homogenous small-sized nanoparticles with higher crystallinity are formed. For Ag
(core)
/Au
(shell)
nanoparticles, at pH 4, best uniformly distributed nanoparticles are formed with higher crystallinity; however for Au
(core)
/Ag
(shell)
nanoparticles, pH 7 is the optimal pH, where uniformly sized nanoparticles with higher crystalline structure are formed.
Graphical Abstract
The article deals with an objective Bayesian analysis for Weibull distribution with application in random censorship model. The objective Bayesian analysis has a long history from Bayes and Laplace ...through Jeffreys and is reaching the level of sophistication gradually. The reference prior method of Bernardo is a nice attempt in this direction. We apply this method to random censorship model using Weibull distribution and compare it with Jeffreys and maximum likelihood methods. It is observed that the closed-form expressions for the Bayes estimators are not possible; we use importance sampling technique to obtain the approximate Bayes estimates. The behaviour of maximum likelihood and Bayes estimators is observed via extensive numerical simulation. The proposed methodology is used for the analysis of a real life application for illustration and appropriateness of the model is tested by Hollander and Proschan goodness-of-fit test specially designed for randomly censored data.
Synergistic integration based on some transition-metal (TM) derived compounds is a unique and appealing technique, especially toward oxygen evolution reaction (OER) under alkaline circumstances. ...Herein, we present a cobalt-selenide (CoSe2) and cobalt-oxide (Co3O4) based composite (CSCO-2) material through a wet chemical method. As-prepared catalyst has been analyzed for various physicochemical characterizations. CSCO-2 offers efficient OER performance in 1.0 M KOH with an overpotential of 252 mV at current density of 20 mA/cm2, with a low Tafel slope value of 69 mV/dec. Importantly, as-prepared catalyst shows stability of 48 h for longer electrochemical performance as a potential candidate for OER.
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•Robust CoSe2 and Co3O4 based electrocatalyst for OER in the alkaline media.•Electrochemical efficiency with lower overpotential of 252 mV and Tafel slope of 69 mV/dec.•Having an electrochemical surface area of 367.5 cm2.•Stability for 48 h as longer performance.
In response to the increasing availability of hydrogen energy and renewable energy sources, molybdenum disulfide (MoS2)-based electrocatalysts are becoming increasingly important for efficient ...electrochemical water splitting. This study involves the incorporation of palladium nanoparticles (PdNPs) into hydrothermally grown MoS2via a UV light assisted process to afford PdNPs@MoS2 as an alternative electrocatalyst for efficient energy storage and conversion. Various analytical techniques, including scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopy (EDS), were used to investigate the morphology, crystal quality, and chemical composition of the samples. Although PdNPs did not alter the MoS2 morphology, oxygen evolution reaction (OER) activity was driven at considerable overpotential. When electrochemical water splitting was performed in 1.0 M KOH aqueous solution with PdNPs@MoS2 (sample-2), an overpotential of 253 mV was observed. Furthermore, OER performance was highly favorable through rapid reaction kinetics and a low Tafel slope of 59 mV dec−1, as well as high durability and stability. In accordance with the electrochemical results, sample-2 showed also a lower charge transfer resistance, which again provided evidence of OER activity. The enhanced OER activity was attributed to a number of factors, including structural, surface chemical compositions, and synergistic effects between MoS2 and PdNPs.
The rationale behind this study was to investigate the potential new low cost and biocompatible aqueous choline based ionic liquid for dissolution and regeneration of silk fibroin obtained from the ...mulberry silkworm. The silk due to its high biocompatibility and mechanical properties finds many applications in the field of biomedical science. Earlier, silk extraction methods have issues of either extraction efficiency or environmental concerns. The ionic liquid is a relatively green solvent was used to dissolve silk fibroin and optimized the process with respect to variables like temperature, time, stirring speed, type of ionic liquid and maximum dissolution ability. The dissolution process was observed through the naked eye as well as using optical microscopy. The optimized conditions at which maximum dissolution i.e. 25% was obtained, are heating the mixture at 50 °C for 2 h. Various analytical characterization such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray diffraction (XRD), Zeta potential, nuclear magnetic resonance (
1
H NMR) and thermogravimetric analysis (TGA) was performed for cocoon, fiber and regenerated silk powder in order to understand the effect of ionic liquid treatment. FTIR, NMR and Raman spectra shows the characteristic peaks assigned to the silk. SEM analysis shows nanoparticles of silk fibroin powder. The crystallinity and thermal stabilities were decreased for regenerated silk as observed from XRD and TGA analysis. The nano-silk exhibited a zeta potential of − 24.6 ± 3 mV.
Recently, the nanostructured nickel–cobalt bimetallic oxide (NiCo2O4) material with high electrochemical activity has received intensive attention. Beside this, the biomass assisted synthesis of ...NiCo2O4 is gaining popularity due to its advantageous features such as being low cost, simplicity, minimal use of toxic chemicals, and environment-friendly and ecofriendly nature. The electrochemical activity of spinel NiCo2O4 is associated with its mixed metal oxidation states. Therefore, much attention has been paid to the crystal quality, morphology and tunable surface chemistry of NiCo2O4 nanostructures. In this study, we have used citrus lemon juice consisting of a variety of chemical compounds having the properties of a stabilizing agent, capping agent and chelating agent. Moreover, the presence of several acidic chemical compounds in citrus lemon juice changed the pH of the growth solution and consequently we observed surface modified and structural changes that were found to be very effective for the development of energy conversion and energy storage systems. These naturally occurring compounds in citrus lemon juice played a dynamic role in transforming the nanorod morphology of NiCo2O4 into small and well-packed nanoparticles. Hence, the prepared NiCo2O4 nanostructures exhibited a new surface-oriented nanoparticle morphology, high concentration of defects on the surface (especially oxygen vacancies), sufficient ionic diffusion and reaction of electrolytic ions, enhanced electrical conductivity, and favorable reaction kinetics at the interface. The electrocatalytic properties of the NiCo2O4 nanostructures were studied in oxygen evolution reaction (OER) at a low overpotential of 250 mV for 10 mA cm−2, Tafel slope of 98 mV dec−1, and durability of 40 h. Moreover, an asymmetric supercapacitor was produced and the obtained results indicated a high specific capacitance of (Cs) of 1519.19 F g−1, and energy density of 33.08 W h kg−1 at 0.8 A g−1. The enhanced electrochemical performance could be attributed to the favorable structural changes, surface modification, and surface crystal facet exposure due to the use of citrus lemon juice. The proposed method of transformation of nanorod to nanoparticles could be used for the design of a new generation of efficient electrocatalyst materials for energy storage and conversion uses.
