Development of Three-Phase Unbalanced Power Flow Using PV and PQ Models for Distributed Generation and Study of the Impact of DG Models

With the increased installations of distributed generators (DGs) within power systems, load flow analysis of distribution systems needs special models and algorithms to handle multiple sources. In this paper, the development of an unbalanced three-phase load flow algorithm that can handle multiple sources is described. This software is capable of switching the DG mode of operation from constant voltage to constant power factor. The algorithm to achieve this in the presence of multiple DGs is proposed. Shipboard power systems (SPS) have other special characteristics apart from multiple sources, which make the load flow difficult to converge. The developed software is verified for a distribution system without DG using the Radial Distribution Analysis Package (RDAP). The developed software analyzes an IEEE test case and an icebreaker ship system. System studies for the IEEE 37-node feeder without the regulator show the effect of different models and varying DG penetration related to the increase in loading. System losses and voltage deviations are compared.     

Application of conducting poly(aniline‐co‐pyrrole) film to cholesterol biosensor

Cholesterol oxidase (ChOx) has been covalently immobilized onto poly(aniline‐co‐pyrrole), electrochemically deposited onto indium‐tin‐oxide (ITO) glass plates, using glutaraldehyde as a crosslinker. These poly (An‐co‐Py)/ChOx films have been characterized using UV–visible spectroscopy fourier transform infrared spectroscopy, scanning electron microscopy, and photometric and amperometric techniques, respectively. The poly(An‐co‐Py)/ChOx bioelectrodes have been utilized for cholesterol estimation in the range of 1–10 mM. The ChOx activity in poly(An‐co‐Py)/ChOx bioelectrode has been found to be the highest at pH 7.0 at 25°C. The sensitivity and stability of poly(An‐co‐Py)/ChOx bioelectrode have been experimentally determined as 93.35 μA/mM and 10 weeks at 4°C, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Poly (pyrrole-co-<Emphasis Type="Italic">N</Emphasis>-methyl pyrrole) for application to cholesterol sensor

Cholesterol oxidase (ChOx) has been electrochemically entrapped onto p-toluene sulphonate (PTS) doped poly (pyrrole-co-N-methyl pyrrole) (1:1) on indium-tin-oxide (ITO) glass plates. This ChOx-copolymer-PTS/ITO bioelectrode has been characterized using cyclic voltammetry (CV), Fourier transform infrared (FTIR) spectroscopy, UV-visible spectroscopy, scanning electron microscopy (SEM) techniques. The cholesterol bioelectrode shows response time of 19 s, linearity from 50 to 400 mg/dL as a function of cholesterol concentration. It exhibits optimum pH range between 6.5 and 7.5, shelf-life of up to 6 weeks at 4 °C and shows almost undisturbed response in presence of interferents like ascorbic acid, uric acid and glucose.     

Two- and three-dimensional models for analysis of optical absorption in tungsten disulphide single crystals

The optical energy gaps of WS₂ single crystal were determined from the analysis of the absorption spectrum near the fundamental absorption edge at room temperature using light parallel to c-axis incident normally on the basal plane. On the basis of two- and three-dimensional models it was found that both direct and indirect band transitions took place in WS₂ bdand the indirect transition was of the allowed type. The optical energy gaps corresponding to both transitions were determined and the phonon energies associated with the indirect transitions estimated. The implications of the results have been discussed.     

Zeolite reinforced carboxymethyl cellulose-Na+-g-cl-poly(AAm) hydrogel composites with pH responsive phosphate release behavior

Phosphate fixation in soils is a matter of concern in agriculture. Conventional application of phosphorus fertilizer suffers from low P use constraint, particularly in acidic soils. Rhizosphere centric slow release strategy bears tremendous prospects. In the present study, monocalcium phosphate (MCP) was impregnated in zeolite reinforced CMC-Na⁺-g-cl-Poly(Aam) hydrogel composites with aim to develop slow phosphate release device for soil application. X-ray diffraction, scanning electron microscopy, and Fourier transform-infrared spectroscopy confirmed the successful synthesis of slow release fertilizer formulations. Presence of zeolite in composite matrix during polymerization resulted in higher MCP loading. The “burst release” phenomena under neutral aqueous environment as compared to diffusion led slow release mechanism under acidic condition suggesting that phosphate release from developed composite matrix was pH responsive. The developed materials possess potential to serve as tool for improving phosphate use efficiency under resource stress agriculture. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47332.     

Quantifying residual stresses in resistance spot welding of 6061-T6 aluminum alloy sheets via neutron diffraction measurements

Residual strains of resistance spot welded joints of 6061-T6 aluminum alloy sheets were measured in three different directions denoted as in-plane longitudinal (σ₁₁), in-plane transversal (σ₂₂), and normal (σ₃₃). The welding process parameters were established to meet or exceed MIL-W-6858D specifications (i.e., approximately 5.7 mm weld nugget and minimum shearing force of 3.8 kN per weld confirmed via quasi-static tensile testing). Electron backscatter diffraction (EBSD) and optical microscopy (OM) were performed to determine grain size and orientation. The residual stress measurements were taken at a series of points along the weld centerline at depths corresponding to the weld mid-plane and at both 1 mm below the top surface of the plate and 1 mm above bottom surface. The residual stresses were captured on the fusion zone (FZ), heat affected zone (HAZ) and base metal (BM) of the resistance spot welded joint. Neutron diffraction results show residual stresses in the weld are approximately 40% lower than yield strength of the parent material. The maximum variation in residual stresses occurs, as expected, in the vertical position of the specimen because of the orientation of electrode clamping forces that produce a non-uniform solidification pattern. Despite the high anisotropy of the welding nugget and surrounding area, a significant result is that σ₃₃ measured stress values are negligible in both the horizontal and vertical directions of the specimen. Consequently, microstructure–property relationships characterized here can indeed inform continuum material models for application in multiscale models.     

Finite element analysis of occupant head injuries: Parametric effects of the side curtain airbag deployment interaction with a dummy head in a side impact crash

In this study, we investigated and assessed the dependence of dummy head injury mitigation on the side curtain airbag and occupant distance under a side impact of a Dodge Neon. Full-scale finite element vehicle simulations of a Dodge Neon with a side curtain airbag were performed to simulate the side impact. Owing to the wide range of parameters, an optimal matrix of finite element calculations was generated using the design method of experiments (DOE); the DOE method was performed to independently screen the finite element results and yield the desired parametric influences as outputs. Also, analysis of variance (ANOVA) techniques were used to analyze the finite element results data. The results clearly show that the influence of moving deformable barrier (MDB) strike velocity was the strongest influence parameter on both cases for the head injury criteria (HIC36) and the peak head acceleration, followed by the initial airbag inlet temperature. Interestingly, the initial airbag inlet temperature was only a ~30% smaller influence than the MDB velocity; also, the trigger time was a ~54% smaller influence than the MDB velocity when considering the peak head accelerations. Considering the wide range in MDB velocities used in this study, results of the study present an opportunity for design optimization using the different parameters to help mitigate occupant injury. As such, the initial airbag inlet temperature, the trigger time, and the airbag pressure should be incorporated into vehicular design process when optimizing for the head injury criteria.     

A Nanoscale Study of Dislocation Nucleation at the Crack Tip in the Nickel-Hydrogen System

Strengthening and embrittlement are controlled by the interactions between dislocations and hydrogen (H)–induced defect structures that can inversely affect the deformation mechanisms in materials. Here we present a simulation framework to understand fundamental issues associated with H-assisted dislocation nucleation and mobility using Monte Carlo (MC) and molecular dynamics (MD). In order to study the interaction between H and dislocations and its effect on material failure, we extensively examined mode I loading of an edge crack using MD simulations. The MD calculations of the total structural energy in the nickel (Ni)–H system shows that H atoms prefer to occupy octahedral interstitial sites in the fcc Ni lattice. As H concentration is increased, the Young’s modulus and the energy required to create free surface decreased, resulting in H-enhanced localized plasticity. The MD simulations also indicate that H not only facilitates dislocation emission from the crack tip but also enhances dislocation mobility, leading to softening of the material ahead of the crack tip. While the decrease in surface energy suggests H embrittlement, the increase in local plasticity induces crack blunting and prohibits crack propagation. The mechanisms responsible for transitioning from a ductile to brittle crack behavior clearly depend on the H concentration and its proximity to the crack tip. Enhanced plasticity will occur within a general field of H atoms that results in lower stacking fault and surface energies, yet H interstitials on preferential slip planes can inhibit dislocation nucleation.     

Size effects on electrical properties of sol–gel grown chromium doped zinc oxide nanoparticles

In this communication, we report the results of the studies on electrical properties of Zn_(0.95)Cr_(0.05)O nanoparticles synthesized using sol–gel method. X–ray diffraction(XRD) and transmission electron microscopy(TEM) measurements were performed for the structural and microstructural behaviors of the nanoparticles. Rietveld analysis was carried out to confirm the single phasic nature. High resolution TEM(HRTEM) confirms the nanoscale nature and polycrystalline orientations in the samples. Dielectric response has been understood in the context of universal dielectric response(UDR) model along with the Koop's theory and Maxwell – Wagner(M–W) mechanism. Variation in ac conductivity with frequency has been discussed in detail in terms of power law fits. Results of the impedance measurements have been explained on the basis of crystal cores and crystal boundary density. Cole – cole behavior has been studied for the impedance data. For potential application of nanoparticles, average normalized change(ANC) in impedance has been estimated and discussed in the light of size effects and oxygen vacancies.